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Cover Page - shares	6 Months Ended
Cover Page - shares	Jun. 30, 2020	Jul. 31, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-36783
Entity Registrant Name	BELLICUM PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-1450200
Entity Address, Address Line One	2130 W. Holcombe Blvd
Entity Address, Address Line Two	Ste. 800
Entity Address, City or Town	Houston
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77030
City Area Code	832
Local Phone Number	384-1100
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	BLCM
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		5,059,779
Entity Central Index Key	0001358403
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Amendment Flag	false

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 66,408	$ 91,028
Restricted cash, current	87	2,788
Accounts receivable, interest and other receivables	127	303
Prepaid expenses and other current assets	1,528	884
Assets held for sale	0	16,851
Total current assets	68,150	111,854
Operating lease right-of-use assets	869	1,042
Property and equipment, net	1,615	2,529
Restricted cash, non-current	1,500	0
Other assets	341	825
Total assets	72,475	116,250
Current liabilities:
Accounts payable	2,486	2,643
Accrued expenses and other current liabilities	7,108	9,770
Warrant derivative liability	28,183	52,184
Private placement option liability	33,970	12,094
Current portion of long-term debt	6,390	11,000
Current portion of lease liabilities	491	454
Liabilities Held-For-Sale, Not Part Of Disposal Group, Current	0	6,273
Total current liabilities	78,628	94,418
Long-term debt, net of deferred issuance costs	20,715	25,717
Long-term lease liabilities	609	864
Total liabilities	99,952	120,999
Commitments and contingencies
Preferred stock: $0.01 par value; 10,000,000 shares authorized	21,308	21,468
Stockholders’ deficit:
Common stock, $0.01 par value; 80,000,000 and 40,000,000 shares authorized at June 30, 2020 and December 31, 2019, respectively, 5,127,525 shares issued and 5,059,779 shares outstanding at June 30, 2020; 5,076,593 shares issued and 5,008,846 shares outstanding at December 31, 2019	51	507
Treasury stock: 67,746 shares held at June 30, 2020 and December 31, 2019	(5,056)	(5,056)
Additional paid-in capital	515,252	511,684
Accumulated other comprehensive loss	(389)	(327)
Accumulated deficit	(558,643)	(533,025)
Total stockholders’ deficit	(48,785)	(26,217)
Total liabilities, preferred stock and stockholders' deficit	$ 72,475	$ 116,250

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	80,000,000	80,000,000
Common stock, issued (in shares)	5,127,525	5,076,593
Common stock, outstanding (in shares)	5,059,779	5,008,846
Treasury stock, shares (in shares)	67,746	67,746
Convertible Preferred Stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized (in shares)	1,517,500	1,517,500
Preferred stock, shares issued (in shares)	534,000	538,000
Preferred stock, outstanding (in shares)	534,000	538,000

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues
Revenues	$ 0	$ 1,391	$ 0	$ 1,907
Operating expenses
Research and development	11,758	20,032	22,206	36,880
General and administrative	3,761	7,518	7,932	15,054
Total operating expenses	15,519	27,550	30,138	51,934
Gain on dispositions, net	(3,761)	0	(3,761)	0
Loss from operations	(11,758)	(26,159)	(26,377)	(50,027)
Other income (expense):
Interest income	28	311	382	721
Interest expense	(763)	(1,088)	(1,748)	(2,158)
Change in fair value of warrant and private placement option liabilities	(30,701)	0	2,125	0
Total other (expense) income	(31,436)	(777)	759	(1,437)
Net loss	$ (43,194)	$ (26,936)	$ (25,618)	$ (51,464)
Net loss per common share attributable to common shareholders, basic and diluted (in shares)	$ (8.55)	$ (5.85)	$ (5.08)	$ (11.40)
Weighted-average shares outstanding, basic and diluted (in shares)	5,052,234	4,605,234	5,045,965	4,515,311
Other comprehensive income (loss):
Unrealized gain on available-for-sale securities, net of tax	$ 0	$ 5	$ 0	$ 56
Foreign currency translation adjustment	(49)	(46)	(62)	(18)
Comprehensive loss	(43,243)	(26,977)	(25,680)	(51,426)
Grants
Revenues
Revenues	$ 0	$ 1,391	$ 0	$ 1,907

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ (Deficit) Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Series 1 redeemable convertible non-voting preferred stock
Balance, beginning of period (in shares) at Dec. 31, 2018		4,424,205	67,746
Balance, beginning of period at Dec. 31, 2018	$ 68,478	$ 442	$ (5,056)	$ 493,784	$ (420,548)	$ (144)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	2,136			2,136
Issuance of common stock upon vesting of restricted stock units (in shares)		2,271
Comprehensive loss	(24,449)				(24,528)	79
Exercise of stock options (in shares)		2,765
Exercise of stock options	70			70
Issuance of common stock in open market transactions, net of issuance costs (in shares)		135,065
Issuance of common stock in open market transactions, net of issuance costs	4,625	$ 14		4,611
Balance, end of period (in shares) at Mar. 31, 2019		4,564,306	67,746
Balance, end of period at Mar. 31, 2019	50,860	$ 456	$ (5,056)	500,601	(445,076)	(65)
Balance, beginning of period (in shares) at Dec. 31, 2018		4,424,205	67,746
Balance, beginning of period at Dec. 31, 2018	68,478	$ 442	$ (5,056)	493,784	(420,548)	(144)
Increase (Decrease) in Stockholders' Equity
Comprehensive loss	(51,426)
Balance, end of period (in shares) at Jun. 30, 2019		4,693,162	67,746
Balance, end of period at Jun. 30, 2019	30,308	$ 469	$ (5,056)	507,013	(472,012)	(106)
Balance, beginning of period (in shares) at Mar. 31, 2019		4,564,306	67,746
Balance, beginning of period at Mar. 31, 2019	50,860	$ 456	$ (5,056)	500,601	(445,076)	(65)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	1,996			1,996
Issuance of common stock upon vesting of restricted stock units (in shares)		585
Comprehensive loss	(26,977)				(26,936)	(41)
Exercise of stock options (in shares)		221
Exercise of stock options	6			6
Issuance of common stock in open market transactions, net of issuance costs (in shares)		124,050
Issuance of common stock in open market transactions, net of issuance costs	4,352	$ 12		4,340
Issuance of common stock - Employee Stock Purchase Plan (in shares)		4,000
Issuance of common stock - Employee Stock Purchase Plan	71	$ 1		70
Balance, end of period (in shares) at Jun. 30, 2019		4,693,162	67,746
Balance, end of period at Jun. 30, 2019	30,308	$ 469	$ (5,056)	507,013	(472,012)	(106)
Preferred stock, beginning balance (in shares) at Dec. 31, 2019							538,000
Preferred stock, beginning balance at Dec. 31, 2019	21,468						$ 21,468
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of redeemable preferred stock into common stock (in shares)		40,000					(4,000)
Conversion of redeemable preferred stock into common stock	(160)	$ (1)		(159)			$ 160
Preferred stock, ending balance (in shares) at Mar. 31, 2020							534,000
Preferred stock, ending balance at Mar. 31, 2020							$ 21,308
Balance, beginning of period (in shares) at Dec. 31, 2019		5,076,593	67,746
Balance, beginning of period at Dec. 31, 2019	(26,217)	$ 507	$ (5,056)	511,684	(533,025)	(327)
Increase (Decrease) in Stockholders' Equity
1-for-10 Reverse Stock Split		$ (457)		457
Share-based compensation	1,323			1,323
Issuance of common stock upon vesting of restricted stock units (in shares)		1,045
Comprehensive loss	17,563				17,576	(13)
Balance, end of period (in shares) at Mar. 31, 2020		5,117,638	67,746
Balance, end of period at Mar. 31, 2020	(7,171)	$ 51	$ (5,056)	513,623	(515,449)	(340)
Preferred stock, beginning balance (in shares) at Dec. 31, 2019							538,000
Preferred stock, beginning balance at Dec. 31, 2019	21,468						$ 21,468
Preferred stock, ending balance (in shares) at Jun. 30, 2020							534,000
Preferred stock, ending balance at Jun. 30, 2020	21,308						$ 21,308
Balance, beginning of period (in shares) at Dec. 31, 2019		5,076,593	67,746
Balance, beginning of period at Dec. 31, 2019	(26,217)	$ 507	$ (5,056)	511,684	(533,025)	(327)
Increase (Decrease) in Stockholders' Equity
Comprehensive loss	(25,680)
Balance, end of period (in shares) at Jun. 30, 2020		5,127,525	67,746
Balance, end of period at Jun. 30, 2020	(48,785)	$ 51	$ (5,056)	515,252	(558,643)	(389)
Preferred stock, beginning balance (in shares) at Mar. 31, 2020							534,000
Preferred stock, beginning balance at Mar. 31, 2020							$ 21,308
Preferred stock, ending balance (in shares) at Jun. 30, 2020							534,000
Preferred stock, ending balance at Jun. 30, 2020	21,308						$ 21,308
Balance, beginning of period (in shares) at Mar. 31, 2020		5,117,638	67,746
Balance, beginning of period at Mar. 31, 2020	(7,171)	$ 51	$ (5,056)	513,623	(515,449)	(340)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	1,564			1,564
Issuance of common stock upon vesting of restricted stock units (in shares)		361
Comprehensive loss	(43,243)				(43,194)	(49)
Issuance of common stock - Employee Stock Purchase Plan (in shares)		9,526
Issuance of common stock - Employee Stock Purchase Plan	65			65
Balance, end of period (in shares) at Jun. 30, 2020		5,127,525	67,746
Balance, end of period at Jun. 30, 2020	$ (48,785)	$ 51	$ (5,056)	$ 515,252	$ (558,643)	$ (389)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (25,618)	$ (51,464)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	2,887	4,132
Depreciation and amortization expense	925	3,742
Change in fair value of warrant and private placement option liabilities	(2,125)	0
Gain on dispositions, net	(3,761)	0
Amortization of discount on investment securities, net	0	(28)
Amortization of right-of-use assets	173	636
Accretion of lease liability	(535)	355
Amortization of deferred issuance costs	388	439
Changes in operating assets and liabilities:
Accounts receivable, interest and other receivables	176	372
Prepaid expenses and other assets	(160)	(2,336)
Accounts payable	(157)	(1,735)
Accrued liabilities and other	(2,662)	1,747
Deferred revenue	0	(1,907)
Net cash used in operating activities	(30,469)	(46,047)
Cash flows from investing activities:
Proceeds from sale of investment securities	0	35,679
Proceeds from sale of property and equipment, net	14,909	0
Purchases of property and equipment	(229)	(551)
Net cash provided by investing activities	14,680	35,128
Cash flows from financing activities:
Payment on debt	(10,000)	0
Proceeds from issuance of common stock in a public offering, net	0	8,977
Proceeds from issuance of stock from employee stock purchase plan	65	71
Proceeds from exercise of stock options	0	76
Payment on financing lease obligations	(35)	(14)
Net cash (used in) provided by financing activities	(9,970)	9,110
Effect of exchange rate changes on cash	(62)	(18)
Net change in cash, cash equivalents, and restricted cash	(25,821)	(1,827)
Cash, cash equivalents and restricted cash at beginning of period	93,816	48,668
Cash, cash equivalents and restricted cash at end of period	67,995	46,841
Supplemental cash flow information:
Cash paid during the period for interest	1,413	1,722
Non-cash investing and financing activities:
Purchases of property and equipment in accounts payables and accrued liabilities	60	0
Conversion of redeemable preferred stock into common stock	160	0
Reclassification of property and equipment, net to assets held for sale	$ 199	$ 0

ORGANIZATION, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

6 Months Ended

Jun. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

ORGANIZATION AND BUSINESS DESCRIPTION

ORGANIZATION, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Organization

Bellicum Pharmaceuticals, Inc. (“Bellicum”) is a clinical stage biopharmaceutical company focused on discovering and developing novel cellular immunotherapies for various forms of cancer, including both hematological cancers and solid tumors. Bellicum is devoting substantially all of its present efforts to developing next-generation product candidates in areas of cellular immunotherapy, including CAR-T and CAR-NK therapy.

Bellicum has two wholly-owned subsidiaries, Bellicum Pharma Limited, a private limited company organized under the laws of the United Kingdom, and Bellicum Pharma GmbH, a private limited liability company organized under German law. Both were formed for the purpose of developing product candidates in Europe. Bellicum, Bellicum Pharma Limited and Bellicum Pharma GmbH are collectively referred to herein as the “Company”. All intercompany balances and transactions among the consolidated entities have been eliminated in consolidation.

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker. The Company has determined that it has one operating and reporting segment as it allocates resources and assesses financial performance on a consolidated basis. The Company’s chief operating decision maker is its Chief Executive Officer who manages operations and reviews the financial information as a single operating segment for purposes of allocating resources and evaluating its financial performance.

Reverse Stock Split

On February 5, 2020, the Company filed a Certificate of Amendment of the Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware to (i) effect a reverse stock split of all issued and outstanding shares of the Company’s common stock at a ratio of 1-for-10 and (ii) reduce the number of authorized shares of the Company’s common stock from 200,000,000 to 40,000,000. On June 15, 2020, the Company filed with the Secretary of State of the State of Delaware a Second Certificate of Amendment to the Company’s Amended and Restated Certificate of Incorporation to increase the authorized number of shares of the Company’s common stock from 40,000,000 shares to 80,000,000 shares.

The accompanying condensed consolidated financial statements and notes to the condensed consolidated financial statements gives retroactive effect to the reverse stock split for all periods presented.

Basis of Presentation

The accompanying unaudited condensed financial statements have been prepared in conformity with the authoritative U.S. generally accepted accounting principles (“GAAP”) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC). Accordingly, the accompanying unaudited condensed consolidated financial statements do not include all of the information and notes required by GAAP for complete financial statements. The unaudited interim financial statements reflect all adjustments, which, in the opinion of management, are necessary for a fair statement of the results for the periods presented. All such adjustments are of a normal and recurring nature. The operating results presented in these unaudited condensed consolidated financial statements are not necessarily indicative of the results that may be expected for any future periods. These unaudited condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto in the Company’s Annual Report on Form 10-K (“Annual Report”) for the fiscal year ended December 31, 2019, as filed with the SEC on March 12, 2020.

The accompanying interim condensed financial statements have been prepared on a basis that assumes that the Company will continue as a going concern, and do not include any adjustments that may result from the outcome of this uncertainty. This basis of accounting contemplates the recovery of the Company’s assets and the satisfaction of the Company’s liabilities and commitments in the normal course of business and does not include any adjustments to reflect the possible future effects of the recoverability and classification of recorded asset amounts or amounts and classification of liabilities that might be necessary should the Company be unable to continue as a going concern. The Company has recorded losses from operations since its inception and if the Company does not successfully obtain regulatory approval and commercialize any of its product candidates, the Company will not be able to achieve profitability. As of June 30, 2020, and December 31, 2019, the Company had an accumulated deficit of $558.6 million and $533.0 million, respectively.

The Company is subject to risks common to companies in the biotechnology industry and the future success of the Company is dependent on its ability to successfully complete the development of, and obtain regulatory approval for, its product candidates, manage the growth of the organization, obtain additional financing necessary in order to develop, launch and commercialize its product candidates, and compete successfully with other companies in its industry.

The Company believes that its current capital resources, which consist of cash and cash equivalents are sufficient to fund operations through at least the next twelve months from the date the accompanying interim financial statements are issued based on the expected cash burn rate. The Company may be required to raise additional capital to fund future operations through the sale of additional equity, incurrence of additional debt allowed under existing debt arrangements, the entry into licensing or collaboration agreements with partners, grants or other sources of financing. Sufficient funds may not be available to the Company at all or on attractive terms when needed from equity or debt financings. If the Company is unable to obtain additional funding from these or other sources when needed, or to the extent needed, it may be necessary to significantly reduce its controllable and variable expenditures and current rate of spending through reductions in staff and delaying, scaling back, or suspending certain research and development, sales and marketing programs and other operational goals.

Reclassifications

Certain reclassifications have been made to prior year financial statements to conform to the current year presentation.

Use of Estimates

The preparation of the interim condensed consolidated financial statements in accordance with GAAP requires management to make certain estimates and judgments that affect the reported amounts of assets, liabilities, and expenses. Actual results could differ from those estimates.

Significant Accounting Policies

There have been no significant changes to the accounting policies during the six months ended June 30, 2020 as compared to the significant accounting policies described in Note 1 of the “Notes to Consolidated Financial Statements” in the Company’s audited financial statements included in its Annual Report for the fiscal year ended December 31, 2019.

Revenue Recognition

Cancer Research Grant Contract

On August 9, 2017, the Company entered into a Cancer Research Grant Contract (the “CPRIT Agreement”) with the Cancer Prevention Research Institute of Texas (“CPRIT”), pursuant to which CPRIT awarded a grant of approximately $16.9 million to the Company to fund development of rivo-cel for hematologic cancer (the “CPRIT Award”). The CPRIT Award is contingent upon funds being available during the term of the CPRIT Agreement and subject to CPRIT’s ability to perform its obligations under the CPRIT Agreement.

During 2017, the Company received $4.2 million in advance funding from CPRIT, which was recorded as deferred revenue. During the three and six month periods ended June 30, 2020, the Company did not incur expenses or recognize revenue for work performed under the CPRIT grant. During the three and six month periods ended June 30, 2019, the Company incurred expenses and recognized revenue of $1.4 million and $1.9 million, respectively, for work performed under the CPRIT grant.

The CPRIT Agreement was due to expire on February 29, 2020, but was terminated early by the Company on January 31, 2020. Upon termination of the CPRIT Agreement, the Company reclassified the remaining unexpended award proceeds of $0.8 million from deferred revenue to accrued liabilities. During the three month period ended June 30, 2020, the Company returned the remaining unexpended award proceeds to CPRIT and released the accrued liability.

Cash, Cash Equivalents and Restricted Cash

The Company considers all short-term, highly liquid investments with maturity of three months or less from the date of purchase and that can be liquidated without prior notice or penalty, to be cash equivalents.

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows.


(in thousands)	June 30, 2020		December 31, 2019
Cash and cash equivalents	$	66,408	$	91,028
Restricted cash, current	87		2,788
Restricted cash, non-current	1,500		—
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$	67,995	$	93,816

During 2017, $4.2 million was received from CPRIT, and is being held in a separate account to be used for costs solely related to the CPRIT grant. Release of the CPRIT funds are subject to the terms of the grant agreement and requirements therein and require the authorization of CPRIT. To date, CPRIT authorized the release of $3.3 million of restricted funds from the CPRIT account. During the three months ended June 30, 2020, the Company returned the remaining unexpended award proceeds to CPRIT, leaving a balance of $0.1 million recorded as restricted cash, requiring the authorization of CPRIT to release, on the accompanying balance sheets at June 30, 2020.

In addition to the restricted cash held and released by CPRIT, there was $1.1 million of restricted cash as of December 31, 2019 in escrow to cover specific construction of manufacturing improvement costs related to the facility lease. The release of the funds was subject to the authorized completion of certain aspects of the manufacturing improvements. The funds were released during the six months ended June 30, 2020.

In connection with the closing of the Asset Purchase Agreement with M.D. Anderson on April 14, 2020, $1.5 million of the cash proceeds received are subject to certain escrow provisions and recorded as restricted cash, non-current. The funds are required to be held for a period of up to 18 months subsequent to the April 14, 2020 closing date.

Disposition of Assets and Liabilities Held for Sale

In 2019, the Company completed the buildout of manufacturing space at its leased headquarters in Houston, Texas and began in-house clinical supply manufacturing. The facility included capacity far in excess of the Company's anticipated current and near-term manufacturing needs and management decided to seek a partner for the facility with the goal of reducing the Company's costs while maintaining dedicated cell therapy manufacturing capacity to support the Company's product candidates.

The disposal of the assets and liabilities of such facility was completed on April 14, 2020, at a purchase price of $15.0 million. The disposal group consisted of property and equipment, net of $12.0 million, right-of-use assets of $4.8 million, current portion of lease liabilities of $1.4 million and long-term lease liabilities of $4.6 million. During the three and six month periods ended June 30, 2020, the Company recognized a net gain of $3.8 million in connection with the disposal, which is presented as Gain on dispositions, net within the accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss. The primary reason for the disposal was to reduce the Company's fixed operating expenses by transitioning from an in-house clinical supply manufacturer to a third party manufacturer.

Accrued Expenses and Other Current Liabilities

Accrued expenses and other liabilities consist of the following:


(in thousands)	June 30, 2020		December 31, 2019
Accrued payroll	$	2,104	$	2,032
Accrued patient treatment costs	954		1,162
Accrued manufacturing costs	273		2,230
Accrued professional services	639		654
Accrued obligations under material supply agreements	1,123		1,121
Accrued other	2,015		2,571
Total accrued expenses and other current liabilities	$	7,108	$	9,770

Warrant Derivatives

Freestanding warrants are classified as liabilities in the accompanying consolidated balance sheets as they are exercisable for multiple underlying instruments that are potentially redeemable. The Company accounts for these warrants at fair value on the date of issuance and are subject to re-measurement to fair value at each balance sheet date. Any change in fair value is recognized as a component of other income (expense) on the accompanying consolidated statements of operations and comprehensive loss. The Company will continue to adjust the liability for changes in fair value until the earlier of the exercise or expiration of the warrants or a change in control, as defined. The warrants are freely exercisable at any time from the issuance date until the expiration date, provided exercise does not cause a warrant holder to exceed a pre-determined beneficial ownership limit.

The Company estimates the fair value of these liabilities using the Black-Scholes valuation technique, which utilizes assumptions including (i) the fair value of the underlying stock at the valuation measurement date, (ii) volatility of the price of the underlying stock, (iii) the expected term, and (iv) risk-free interest rates.

Private Placement Option

The Company has entered into a security purchase agreement that contains a call option on preferred shares that are callable outside the control of the Company. The Company recorded the option as a liability and measured the fair value of the option at the time of issuance. The Company will re-measure the option to fair value at each balance sheet date and record changes in fair value in other income (expense) in the accompanying condensed consolidated statement of operations and comprehensive loss at each reporting period. Offering expenses arising from the issuance of the private placement option were expensed as incurred.

The Company estimates the fair value of these liabilities using a binomial lattice model, which utilizes assumptions including (i) the fair value of the underlying stock at the valuation measurement date, (ii) volatility of the price of the underlying stock, (iii) the expected term, and (iv) risk-free interest rates.

Preferred Stock

Preferred shares issued by the Company that are subject to mandatory redemption are classified as liability instruments in the accompanying condensed consolidated balance sheets and are measured at fair value at the date of issuance. Conditionally redeemable preferred shares (including preferred shares that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified within mezzanine equity in the accompanying condensed consolidated balance sheets. At all other times, preferred shares are classified within stockholders’ (deficit) equity.

Operating Leases

At the inception of a contractual arrangement, the Company determines whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. If both criteria are met, upon lease commencement, the Company records a lease liability which represents the Company’s obligation to make lease payments arising from the lease, and a corresponding right-of-use (“ROU”) asset which represents the Company’s right to use an underlying asset during the lease term.

Operating leases are recognized as ROU assets and operating lease liabilities on the balance sheet based on the present value of the future minimum lease payments over the lease term at commencement date calculated using the Company's incremental borrowing rate applicable to the underlying asset unless the implicit rate is readily determinable. Any lease incentives received are deferred and recorded as a reduction of the ROU asset and amortized over the term of the lease. Rent expense, comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term. The Company determines the lease term as the non-cancellable period of the lease and may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Leases with a term of 12 months or less are not recognized on the balance sheets.

Fair Value of Financial Instruments

Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in an orderly transaction between market participants in a principal market on the measurement date.

Accounting standards include disclosure requirements around fair values used for certain financial instruments and establish a fair value hierarchy. The three-tier hierarchy defines a three-tiered valuation hierarchy for disclosures that prioritizes valuation inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market, as described further in Note 2.

Observable inputs reflect readily obtainable data from independent sources, and unobservable inputs reflect the Company’s market assumptions.

These inputs are classified into the following hierarchy:

Level 1 Inputs - quoted prices (unadjusted) in active markets for identical assets that the reporting entity has the ability to access at the measurement date;

Level 2 Inputs - inputs other than quoted prices included within Level 1 that are observable for the asset, either directly or indirectly; and

Level 3 Inputs - unobservable inputs for the assets.

The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

The Company believes the recorded values of its financial instruments, including cash and cash equivalents, accounts payable, accrued liabilities, and debt approximate their fair values due to the short-term nature of these instruments.

Financial Instruments and Credit Risks

Financial instruments that potentially subject the Company to credit risk include cash and cash equivalents and accounts receivable. Cash is deposited in demand accounts in federally insured domestic institutions to minimize risk. Insurance is provided through the Federal Deposit Insurance Corporation and Security Investor Protection Corporation. Although the balances in these accounts exceed the federally insured limit from time to time, the Company has not incurred losses related to these deposits.

Equity Issuance Costs

Equity issuance costs represent costs paid to third parties in order to obtain equity financing. The costs related to preferred and common stock have been netted against the proceeds of the equity issuances.

Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders

Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period without consideration for common stock equivalents. Diluted earnings per share is based on the treasury stock method and includes the effect from potential issuance of ordinary shares, such as shares issuable pursuant to the conversion of preferred stock to common stock, exercise of warrants to purchase common stock, exercise of stock options, and vesting of restricted stock units.

The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per share of common stock attributable to common stockholders for the periods presented as the effect of including such securities would be anti-dilutive.


	June 30, 2020	June 30, 2019
Common Stock Equivalents:	Number of Shares
Redeemable convertible series 1 preferred stock	5,340,000	—
Warrants to purchase common stock	5,750,000	—
Private placement option	9,675,000	—
Options to purchase common stock	1,122,938	766,533
Unvested shares of restricted stock units	187,705	21,593
Total common stock equivalents	22,075,643	788,126

New Accounting Requirements and Disclosures

Fair Value Measurement

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which modifies fair value disclosures and removes some disclosure requirements for both public and private companies. In addition, public companies are subject to some new disclosure requirements which requires to disclose the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. ASU No. 2018-13 is effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company adopted the standard effective January 1, 2020 with no material effect on its financial statements.

Financial Instruments – Credit Losses

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires the measurement of all expected credit losses for financial assets including trade receivables held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. ASU No. 2016-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The Company adopted the standard effective January 1, 2020 with no material effect on its financial statements. Subsequent to the issuance of ASU 2016-13, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses. This ASU does not change the core principle of the guidance in ASU 2016-13, instead these amendments are intended to clarify and improve operability of certain topics included within the credit losses guidance. The FASB also subsequently issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Derivatives and Hedging (Topic 815), and Financial Instruments (Topic 842), which did not change the core principle of the guidance in ASU 2016-13 but clarified that expected recoveries of amounts previously written off and expected to be written off should be included in the valuation account and should not exceed amounts previously written off and expected to be written off. The guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2019 for public business entities, excluding smaller reporting companies. Early adoption is permitted. As a smaller reporting company, the guidance will be effective for the Company during the first quarter of 2023. The Company is in the process of assessing the impact adoption will have on its consolidated financial statements.

Income Taxes

In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740). The guidance eliminates certain exceptions for recognizing deferred taxes for investments, performing intraperiod allocation and calculating income taxes in interim periods. This guidance also includes guidance to reduce complexity in certain areas, including recognizing deferred taxes for tax goodwill and allocating taxes to members of a consolidated group. ASU 2019-12 is effective for annual and interim periods in fiscal years beginning after December 15, 2020. Early adoption is permitted. The Company is currently evaluating the impact this change will have on its consolidated financial statements.

Investments

In January 2020, the FASB issued Accounting Standards Update No. 2020-01, Investments—Equity Securities (Topic 321), Investments—Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815)—Clarifying the Interactions between Topic 321, Topic 323, and Topic 815 (a consensus of the Emerging Issues Task Force), which clarifies the interaction of the accounting for equity securities, investments accounted for under the equity method, and certain forward contracts and purchased options. This update is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years, and early adoption is permitted. The Company is in the process of determining the impact the adoption will have on its consolidated financial statements as well as whether to early adopt the new guidance.

FAIR VALUE MEASUREMENTS AND INVESTMENT SECURITIES

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS AND INVESTMENT SECURITIES

Investment Securities

The following table presents the Company’s investment securities (including, if applicable, those classified on the Company’s balance sheet as cash equivalents) that are measured at fair value on a recurring basis:


	Fair Value at June 30, 2020										Fair Value at December 31, 2019
(in thousands)	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds and treasury bills	$	55,253	$	—	$	—	$	77,170	$	—	$	—
Total cash equivalents	$	55,253	$	—	$	—	$	77,170	$	—	$	—

As of June 30, 2020, the $1.5 million of restricted cash, non-current, on the Company's balance sheet is held in a money market fund.

Money market funds, U.S. Treasury, U.S. government agency-backed securities, corporate debt securities and municipal bonds are valued based on various observable inputs such as benchmark yields, reported trades, broker/dealer quotes, benchmark securities and bids.

Warrant Derivative Liability and Private Placement Option Liability

The Company's financial liabilities recorded at fair value on a recurring basis include the fair values of the warrant derivative liability and the private placement option liability. As of June 30, 2020, the fair values of the warrant derivative liability and the private placement option liability are classified as current liabilities in the accompanying condensed consolidated balance sheets. These liabilities will be shown as current liabilities on the balance sheet when it is deemed more probable than not by management to be exercised within one year.

The fair value of the warrants has been estimated with the following weighted-average assumptions:


	June 30, 2020		December 31, 2019
Risk-free interest rate	0.41	%	1.83	%
Volatility of underlying stock price	90.00	%	78.67	%
Expected term (years)	6.14		6.64

The fair value of the private placement option has been estimated with the following weighted-average assumptions:


	June 30, 2020
Risk-free interest rate	0.59	%
Volatility of underlying stock price	90.00	%
Expected term (years)	7.00

The following table provides the warrant derivative and private placement option reported at fair value and measured on a recurring basis:


	Fair Value at June 30, 2020										Fair Value at December 31, 2019
(in thousands)	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Warrant derivative liability	$	—	$	—	$	28,183	$	—	$	—	$	52,184
Private placement option liability	—		—		33,970		—		—		12,094
Total fair value	$	—	$	—	$	62,153	$	—	$	—	$	64,278

The ending balance of the Level 3 financial instruments presented above represents management's best estimate of valuation and may not be substantiated by comparison to independent markets and, in many cases, could not be realized in immediate settlement of the instruments.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

LEASES

6 Months Ended

Jun. 30, 2020

Leases [Abstract]

LEASES

The Company determines whether an arrangement is a lease at its inception. Operating leases relate primarily to office space with remaining lease terms of two years. If operating leases include options to extend the lease term, management will consider the options in determining the lease term used to establish the Company's ROU assets and lease liabilities.

As most of the Company's leases do not provide an implicit rate, the Company's incremental borrowing rate based on the information available at lease commencement date was used to determine the present value of lease payments.

Components of lease cost are as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
(in thousands)	2020		2019		2020		2019
Finance lease cost:
Amortization of leased asset	$	18	$	18	$	36	$	24
Interest on lease liabilities	6		7		12		10
Operating lease cost	194		547		499		993
Short-term lease cost	207		12		241		47
Total lease cost	$	425	$	584	$	788	$	1,074


	June 30, 2020
Weighted-average remaining lease term:
Operating leases	2.10 years
Finance leases	1.90 years
Weighted-average discount rate:
Operating leases	12.77	%
Finance leases	13.28	%

Supplemental cash flow information and non-cash activity related to the Company's operating leases are as follows:


	Six Months Ended June 30,
(in thousands)	2020				2019
Operating cash flow information:
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases			$	819			$	1,095
Operating cash flows from finance leases	12				10
Financing cash flows from finance leases	35				14
Non-cash activity:
Right-of-use assets obtained in exchange for lease obligations	$	—			$	1,259

Maturities of lease liabilities by year for leases are as follows:


(in thousands)	Operating Leases		Financing Leases
2020	$	252	$	48
2021	515		90
2022	316		39
2023 and beyond	—		—
Total lease payments	1,083		177
Less: Imputed interest	(139)		(21)
Present value of lease liabilities	$	944	$	156

DEBT	6 Months Ended
DEBT	Jun. 30, 2020
Debt Disclosure [Abstract]
DEBT	DEBT On December 21, 2017 (the “Oxford Closing Date”), the Company entered into a loan and security agreement with Oxford Finance LLC, as the collateral agent and a lender ("Oxford"), and the lenders listed on Schedule 1.1 thereto or otherwise party thereto from time to time (the "Lenders"), pursuant to which the Company borrowed $35.0 million in a single term loan (the “Oxford Loan”) on the Oxford Closing Date. On the Oxford Closing Date, the Company used approximately $32.9 million of the proceeds from the Oxford Loan to repay its indebtedness to a previous lender. On December 24, 2019, the Company entered into a First Amendment to Loan and Security Agreement (the “First Amendment”) with Oxford, in connection with the Asset Sale with M.D. Anderson. On March 31, 2020, the Company entered into a Second Amendment to Loan and Security Agreement (the "Second Amendment") with Oxford Finance LLC, in connection with the Asset Sale. The loan and security agreement with Oxford, as amended by the First and Second Amendment, is referred to as the "Oxford Loan Agreement." The Company’s obligations under the Oxford Loan Agreement are secured by a first priority security interest in substantially all of the Company’s current and future assets, including its intellectual property. The Company has also agreed not to encumber its intellectual property assets, except as permitted by the Oxford Loan Agreement. The Oxford Loan matures on December 1, 2022 (the “Oxford Maturity Date”) and was originally interest-only through January 31, 2020, followed by 35 equal monthly payments of principal and unpaid accrued interest. The Oxford Loan bears interest at a floating per annum rate equal to (i) 7.25% plus (ii) the greater of (a) the 30-day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue and (b) 1.25%. The Company will be required to make a final payment of 8.70% of the principal amount of the Oxford Loan borrowed (the “Oxford Final Payment Fee”), payable on the earlier of (i) the Oxford Maturity Date, (ii) the acceleration of the Oxford Loan, or (iii) the prepayment of the Oxford Loan. The Company may prepay all, but not less than all, of the borrowed amounts, provided that the Company will be obligated to pay a prepayment fee equal to (i) 3.00% of the outstanding principal balance if prepaid on or before the first anniversary of the Closing Date, (ii) 2.00% of the outstanding principal balance, if prepaid after the first anniversary and before the second anniversary of the Closing Date, and (iii) 1.00% of the outstanding principal balance prepaid thereafter and prior to the Maturity Date (each, a “Prepayment Fee”). While any amounts are outstanding under the Oxford Loan Agreement, the Company is subject to a number of affirmative and restrictive covenants, including covenants regarding delivery of financial statements, payment of taxes, maintenance of insurance, dispositions of property, business combinations or acquisitions, incurrence of additional indebtedness and transactions with affiliates, among other customary covenants. The Company is also restricted from paying dividends or making other distributions or payments of its capital stock, subject to limited exceptions. Upon the occurrence of certain events, including but not limited to the Company’s failure to satisfy its payment obligations under the Oxford Loan Agreement, the breach of certain of its other covenants under the Oxford Loan Agreement, or the occurrence of a material adverse change, the collateral agent will have the right, among other remedies, to declare all principal and interest immediately due and payable, and the lender will have the right to receive the Oxford Final Payment Fee and, if the payment of principal and interest is due prior to the Oxford Maturity Date, a Prepayment Fee. Pursuant to the Second Amendment, the Loan Agreement was amended to, among other things: (i) provide for Oxford's and the Lenders’ consent to the Company’s consummation of the Asset Sale with M.D. Anderson, provided such sale occurs on or prior to June 30, 2020; (ii) if such Asset Sale occurs on or prior to June 30, 2020, extend the interest-only period through as late as July 31, 2021; (iii) if Asset Sale closes on or prior to June 30, 2020, provide for a partial repayment to the Lenders of a significant percentage of the proceeds of the asset sale that varies in accordance with the timing of closing and the associated amortization schedule, a portion of which will be applied as partial payment of the Final Payment Percentage (as defined in the Loan Agreement); and (iv) grant the Lenders and Oxford a security interest in the Company’s intellectual property as of the date of the Second Amendment, in each case as set forth in the Second Amendment. The sale of certain assets subject to the Second Amendment closed on April 14, 2020. Pursuant to the Second Amendment, the closing of the Asset Sale to M.D. Anderson triggered the Company’s obligation to provide partial repayment to the Lenders of $7.0 million, of which $0.6 million was applied as partial payment of the Oxford Final Payment Fee. The interest-only period was extended through December 31, 2020. The Company paid expenses related to the Oxford Loan Agreement of $0.1 million, which, along with the final facility charge of $3.0 million, have been recorded as deferred issuance costs, which offset long-term debt on the Company's condensed consolidated balance sheet. The deferred issuance costs are being amortized over the term of the loan as interest expense using the effective interest method. Interest expense of amortized deferred issuance costs included $0.2 million and $0.2 million during the three months ended June 30, 2020 and 2019, respectively, and $0.4 million and $0.4 million during the six months ended June 30, 2020 and 2019, respectively. The interest rate on amounts borrowed under the Oxford Loan Agreement was 10.98% at June 30, 2020. Management believes that the carrying value of the debt facility approximates its fair value, as the Company's debt facility bears interest at a rate that approximates prevailing market rates for instruments with similar characteristics. The fair value of the Company's debt facility is determined under Level 2 in the fair value hierarchy.

AUGUST 2019 PUBLIC OFFERING AND PRIVATE PLACEMENT

6 Months Ended

Jun. 30, 2020

Statement of Stockholders' Equity [Abstract]

AUGUST 2019 PUBLIC OFFERING AND PRIVATE PLACEMENT

August 2019 Public Offering

On August 16, 2019, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with Jefferies LLC and Wells Fargo Securities, LLC, as representatives of the several underwriters named therein (the “Underwriters”), relating to an underwritten public offering (the “Offering”) of 575,000 shares of the Series 1 Redeemable Convertible Non-Voting Preferred Stock of the Company (the “Series 1 Preferred Stock”) and warrants (the “Public Warrants”) to purchase up to 5,750,000 shares of its common stock. Each share of Series 1 Preferred Stock was sold together with a warrant to purchase 10 shares of common stock at a combined price to the public of $100.00. Under certain circumstances, each warrant to purchase 10 shares of common stock will be exercisable, at the irrevocable election of the holder, for one share of Series 1 Preferred Stock. The offering closed on August 21, 2019, and the net proceeds to the Company from the Offering was approximately $53.8 million after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company, and excluding any proceeds that the Company may receive upon exercise of the Public Warrants.

All of the Public Warrants sold in the Offering have an exercise price of $13.00 per share of common stock or, in certain circumstances, for $130.00 per share of Series 1 Preferred Stock, subject to proportional adjustments in the event of stock splits or combinations or similar events. The Public Warrants were immediately exercisable upon issuance, provided that the holder is prohibited, subject to certain exceptions, from exercising a warrant for shares of common stock to the extent that immediately prior to or after giving effect to such exercise, the holder, together with its affiliates and other attribution parties, would own more than 9.99% of the total number of shares of common stock then issued and outstanding, which percentage may be changed at the holder’s election to a lower percentage at any time or to a higher percentage not to exceed 19.99% upon 61 days’ notice to the Company. The Public Warrants will expire on August 21, 2026, unless exercised prior to that date.

Private Placement

On August 16, 2019, the Company entered into a Securities Purchase Agreement (the “Securities Purchase Agreement”) with certain institutional investors named therein (the “Purchasers”), pursuant to which the Company agreed to issue in a private placement (i) 350,000 shares of its Series 2 Redeemable Convertible Non-Voting Preferred Stock (the “Series 2 Preferred Stock”), at a purchase price of $100.00 per share, and related warrants (the “Private Warrants”) to purchase up to 2,800,000 shares of common stock at an exercise price of $10.00 per share, and (ii) 250,000 shares of its Series 3 Redeemable Convertible Non-Voting Preferred Stock (the “Series 3 Preferred Stock” and, together with the Series 1 Preferred Stock and Series 2 Preferred Stock, the “Preferred Stock”), at a purchase price of $140.00 per share, and related warrants (also, “Private Warrants”) to purchase up to 875,000 shares of common stock at an exercise price of $14.00 per share. The purchase and sale of the securities issuable under the private placement agreement may occur in two or more separate closings, each to be conducted at the Purchasers’ discretion within five days’ notice to the Company. The purchase and sale was subject to the Company’s obtaining stockholder approval for additional authorized shares of Common Stock or a reverse stock split (the “Required Stockholder Approval”), which occurred in the first quarter of 2020. The right of the Purchasers to purchase such securities will expire two and a half years after the Required Stockholder Approval, on July 15, 2022, with respect to the Series 2 Preferred Stock, and three years after such stockholder approval, on January 15, 2023, with respect to the Series 3 Preferred Stock, if not exercised prior to that date.

The Company received $11.2 million in option proceeds, net of offering costs, upon the execution of the Securities Purchase Agreement. Total offering costs incurred by the Company related to the Public Warrants, Private Warrants and options amounted to $3.0 million.

The following table reflects the fair value roll forward reconciliation of the warrant derivative and private placement option liabilities for the period ended June 30, 2020:


(in thousands)	Warrant Derivative Liability		Private Placement Option Liability		Total
Balance, December 31, 2019	$	52,184	$	12,094	$	64,278
Change in fair value	(24,001)		21,876		(2,125)
Balance, June 30, 2020	$	28,183	$	33,970	$	62,153

REDEEMABLE CONVERTIBLE PREFERRED STOCK	6 Months Ended
REDEEMABLE CONVERTIBLE PREFERRED STOCK	Jun. 30, 2020
Equity [Abstract]
REDEEMABLE CONVERTIBLE PREFERRED STOCK	REDEEMABLE CONVERTIBLE PREFERRED STOCK In August 2019, the Company sold Series 1 preferred stock pursuant to the Offering. The Company has 10,000,000 authorized shares of preferred stock with a par value of $0.01, of which the Company has designated 1,517,500 shares as Series 1 redeemable convertible non-voting preferred stock, 350,000 shares as Series 2 redeemable convertible non-voting preferred stock and 250,000 shares as Series 3 redeemable convertible non-voting preferred stock. There were 534,000 shares of Series 1 preferred stock issued and outstanding as of June 30, 2020. There were no shares of Series 2 or 3 preferred stock issued and outstanding as of June 30, 2020. As of June 30, 2020, the Company classified the Series 1 preferred stock within mezzanine equity, as the Series 1 preferred stock is redeemable at the option of the holders upon passage of time, which is outside of the Company’s control to prevent. The Series 1 preferred stock is not currently redeemable and is only redeemable upon a fundamental change at a redemption price. The Company does not believe a fundamental change is considered probable until it occurs. Subsequent adjustment of the amount presented within mezzanine equity to its redemption amount is unnecessary if it is not probable that the instrument will become redeemable. As (i) the Series 1 preferred stock is only redeemable upon a fundamental change, the occurrence of which is not probable, and (ii) the occurrence of Transition Date (defined below) is probable, the Company did not accrete the Series 1 preferred stock to its redemption amount. Optional Conversion Each share of Preferred Stock is initially convertible into 10 shares of Common Stock. The conversion price at which Preferred Stock may be converted into shares of common stock, is subject to adjustment in connection with certain specified events. Redemption Until the applicable Transition Date (defined below), at any time on or after the date that is the fifth (5th) anniversary of the initial issue date of the applicable series of preferred stock, all or any portion of the preferred stock is redeemable at the option of the holder at a redemption price of $100.00 per share (for Series 1 and Series 2 preferred stock) and $140.00 per share (for Series 3 preferred stock). The “Transition Date” means: •With respect to the Series 1 preferred stock, the first date following August 21, 2021, on which each of the Conditions (as defined below) is met (the “Series 1 Transition Date”); •With respect to the Series 2 preferred stock, the first date following the six-month anniversary of the Series 1 Transition Date on which each of the Conditions is met (the “Series 2 Transition Date”); and •With respect to the Series 3 preferred stock, the first date following the six-month anniversary of the Series 2 Transition Date on which each of the Conditions is met. The “Conditions” mean: (1) the closing price of the Company’s common stock has been equal to or exceeded $25.00 per share for 180 calendar days (for determining if the Conditions are met for the Series 1 preferred stock and Series 2 preferred stock) and $35.00 per share (for the Series 3 preferred stock) for 180 calendar days; (2) the 50-day average trading volume of the Company’s common stock on the Nasdaq stock market is greater than 50,000 shares; and (3) a Phase 3 or Phase 2 pivotal clinical trial for one of the Company’s CAR T product candidates has been initiated, meaning that at least one clinical trial site has been activated. Dividends Shares of Preferred Stock will be entitled to receive dividends equal to (on an as-if-converted-to-common stock basis), and in the same form and manner as, dividends actually paid on shares of common stock. Liquidation Until the applicable Transition Date, in the event of a liquidation, dissolution, winding up or deemed liquidation, holders of the Preferred Stock will receive a payment equal to the applicable per share purchase price of their Preferred Stock before any proceeds are distributed to the holders of Common Stock. The liquidation preferences, protective voting provisions and redemption rights of the Preferred Stock will terminate upon the occurrence of certain events. Voting Shares of Preferred Stock will generally have no voting rights, except to the extent expressly provided in the Company’s certificate of incorporation or as otherwise required by law.

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS

Stockholders' Equity

On October 5, 2018, the Company entered into an Open Market Sale Agreement (the “Sale Agreement”) with Jefferies LLC ("Jefferies"), as sales agent, pursuant to which the Company may offer and sell, from time to time, through Jefferies, shares of the Company’s common stock having an aggregate offering price of up to $60.0 million. The shares will be offered and sold pursuant to the Company’s prospective supplement to its shelf registration statement on Form S-3 (the “Prospective Supplement”). During the year ended December 31, 2019, the Company received $9.0 million in net proceeds from the sale of 259,115 shares of its common stock in the open market. On August 16, 2019, in connection with the Offering, the Company delivered written notice to Jefferies that the Company was suspending and terminating the Prospectus Supplement related to the shares of its common stock issuable pursuant to the Sale Agreement. The Company will not make any sales of its securities pursuant to the Sales Agreement, unless and until a new prospectus supplement is filed. Other than the termination of the Prospectus Supplement, the Sale Agreement remains in full force and effect.

Share-Based Compensation Plans

The Company has five share-based compensation plans, including the 2019 Equity Incentive Plan (the "2019 Plan"), which was adopted in June 2019. Each plan authorizes the granting of shares of common stock and options to purchase common stock to employees and directors of the Company, as well as non-employee consultants, and allows the holder of the option to purchase common stock at a stated exercise price. The only plan under which the Company may currently grant equity awards is the 2019 Equity Incentive Plan although there remain outstanding awards under the other four plans. Options vest according to the terms of the grant, which may be immediately or based on the passage of time, generally over four years, and have a term of up to 10 years. Unexercised stock options terminate on the expiration date of the grant. The Company recognizes the share-based compensation expense over the requisite service period of the individual grantees, which generally equals the vesting period.

2019 Equity Incentive Plan

The 2019 Plan, is designed to secure and retain the services of the Company’s employees and directors. The 2019 Plan is successor to and continuation of the 2014 Equity Incentive Plan, as amended, the ("2014 Plan"), and no additional awards may be issued from the 2014 Plan. Subject to adjustment for certain changes in the Company’s capitalization, the aggregate number of shares of common stock that may be issued under the 2019 Plan (the "Share Reserve") will not exceed the sum of (i) 250,000 new shares, plus (ii) an additional 600,000 shares that were approved at the Company’s Special Meeting of Stockholders in January 2020, plus (iii) an additional 500,000 shares that were approved at the Company's Annual Meeting of Stockholders in June 2020, and plus (iv) the Prior Plans’ Returning Shares, as defined in the 2019 Plan documents, in an amount not to exceed 600,540 shares, including any stock award granted under the 2014 Plan, 2011 Stock Option Plan, as amended, or 2006 Stock Option Plan, as amended, that were outstanding as of the date the 2019 Plan was approved by the Company's stockholders, as such shares become available from time to time.

The following shares of common stock (the "2019 Plan Returning Shares") will also become available again for issuance under the 2019 Plan: (i) any shares subject to a stock award granted under the 2019 Plan that are not issued because such stock award expires or otherwise terminates without all of the shares covered by such stock award having been issued; (ii) any shares subject to a stock award granted under the 2019 Plan that are not issued because such stock award is settled in cash; and (iii) any shares issued pursuant to a stock award granted under the 2019 Plan that are forfeited back to or repurchased by the Company because of a failure to vest.

The 2019 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards, and other stock awards.

The following table summarizes the stock option activity for all stock plans during the six months ended June 30, 2020:


			Options and Inducement Awards
Outstanding at December 31, 2019			567,842
Granted			634,085
Exercised			—
Forfeited			(78,989)
Outstanding at June 30, 2020			1,122,938
Exercisable at June 30, 2020			335,278

The following table summarizes the stock award activity for all stock plans during the six months ended June 30, 2020:


			Restricted Stock Awards and Units
Outstanding at December 31, 2019			6,359
Granted			207,547
Vested			(2,309)
Forfeited			(23,892)
Outstanding at June 30, 2020			187,705

2014 Employee Stock Purchase Plan

The 2014 Employee Stock Purchase Plan (the "ESPP") provides for eligible Company employees, as defined by the ESPP, to be given an opportunity to purchase the Company's common stock at a discount, through payroll deductions, with stock purchases being made upon defined purchase dates. The ESPP authorizes the issuance of up to 55,000 shares of the Company’s common stock to participating employees and allows eligible employees to purchase shares of common stock at a 15% discount from the lesser of the grant date or purchase date fair market value. During the six-month periods ended June 30, 2020 and 2019 there were 9,526 and 4,000 shares purchased by the ESPP, respectively.

A summary of activity within the ESPP follows:


	Six Months Ended June 30,
(in thousands)	2020		2019
Deductions from employees	$	62	$	48
Share-based compensation expense recognized	46		57
Remaining share-based compensation expense	144		135

As of June 30, 2020, there were 23,937 shares available for issuance under the ESPP.

Share-Based Compensation Expense

The fair value of option grants is determined using the Black-Scholes option-pricing model and has been estimated with the following weighted-average assumptions:


	Six Months Ended June 30,
	2020		2019
Risk-free interest rate	1.24	%	2.25	%
Volatility	81.53	%	72.10	%
Expected life (years)	6.04		6.08
Expected dividend yield	—		—

Share-based compensation expense by classification for the three and six months ended June 30, 2020 and 2019 are as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
(in thousands)	2020		2019		2020		2019
Research and development	$	661	$	959	$	1,209	$	2,024
General and administrative	903		1,037		1,678		2,108
Total	$	1,564	$	1,996	$	2,887	$	4,132

At June 30, 2020, total compensation cost not yet recognized was $9.4 million and the weighted-average period over which this amount is expected to be recognized is 2.3 years.

COMMITMENTS AND CONTINGENCIES	6 Months Ended
COMMITMENTS AND CONTINGENCIES	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Co-Development and Co-Commercialization Agreement - Adaptimmune Therapeutics plc On December 16, 2016, the Company entered into a Co-Development and Co-Commercialization Agreement with and Adaptimmune Therapeutics plc ("Adaptimmune") in order to facilitate a staged collaboration to evaluate, develop and commercialize next generation T cell therapies. Under the Agreement, the parties agreed to evaluate the Company’s GoTCR technology (inducible MyD88/CD40 co-stimulation, or "iMC") with Adaptimmune’s affinity-optimized SPEAR® T cells for the potential to create enhanced TCR product candidates. Depending on results of the preclinical proof-of-concept phase, the parties expect to progress to a two-target co-development and co-commercialization phase. To the extent necessary, and in furtherance of the parties’ proof-of-concept and co-development efforts, the parties granted each other a royalty-free, non-transferable, non-exclusive license covering their respective technologies for purposes of facilitating such proof-of-concept and co-development efforts. In addition, as to covered therapies developed under the agreement, the parties granted each other a reciprocal exclusive license for the commercialization of such therapies. With respect to any joint commercialization of a covered therapy, the parties agreed to negotiate in good faith the commercially reasonable terms of a co-commercialization agreement. The parties also agreed that any such agreement shall provide for, among other things, equal sharing of the costs of any such joint commercialization and the calculation of profit shares as set forth in the Agreement. The Agreement will expire on a country-by-country basis once the parties cease commercialization of the T cell therapies covered by the Agreement, unless earlier terminated by either party for material breach, non-performance or cessation of development, bankruptcy/insolvency, or failure to progress to co-development phase. License Agreement - Baylor In March 2016, the Company and Baylor College of Medicine (“BCM”) entered into two additional license agreements pursuant to which the Company obtained exclusive rights to technologies and patent rights owned by BCM. The Company paid BCM a nonrefundable license fee of $100,000 and could incur additional payments upon the achievement of certain milestone events as set forth in the agreement. If the Company is successful in developing any of the licensed technologies, resulting sales would be subject to a royalty payment in the low single digits. License Agreement - Agensys, Inc. On December 10, 2015, the Company and Agensys, Inc. (“Agensys”), entered into a license agreement (the “Agensys Agreement”), pursuant to which (i) Agensys granted the Company, within the field of cell and gene therapy of diseases in humans, an exclusive, worldwide license and sublicense to its patent rights directed to prostate stem cell antigen 1 (“PSCA”) and related antibodies, and (ii) the Company granted Agensys a non-exclusive, fully paid license to the Company’s patents directed to inventions that were made by the Company in the course of developing the Company’s licensed products, solely for use with Agensys therapeutic products containing a soluble antibody that binds to PSCA or, to the extent not based upon the Company’s other proprietary technology, to non-therapeutic applications of antibodies not used within the field. As consideration for the rights granted to the Company under the Agreement, the Company agreed to pay to Agensys a non-refundable upfront fee of $3.0 million, which was included in license fee expense. The Company is also required to make aggregate milestone payments to Agensys of up to (i) $5.0 million upon the first achievement of certain specified clinical milestones for its licensed products, (ii) $50.0 million upon the achievement of certain specified clinical milestones for each licensed product, and (iii) $75.0 million upon the achievement of certain sales milestones for each licensed product. The Agreement additionally provides that the Company will pay to Agensys a royalty that ranges from the mid to high single digits based on the level of annual net sales of licensed products by the Company, its affiliates or permitted sublicensees. The royalty payments are subject to reduction under specified circumstances. These milestone and royalty payments will be expensed as incurred. Under the Agreement, Agensys also was granted the option to obtain an exclusive license, on a product-by-product basis, from the Company to commercialize in Japan each licensed product developed under the Agensys Agreement that has completed a phase 2 clinical trial. As to each such licensed product, if Agensys or its affiliate, Astellas Pharma, Inc., exercises the option, the Agensys Agreement provides that the Company will be paid an option exercise fee of $5.0 million. In addition, the Agensys Agreement provides that the Company will be paid a royalty that ranges from the mid to high single digits based on the level of annual net sales in Japan of each such licensed product. If the option is exercised, the aggregate milestone payments payable by the Company to Agensys, described above with respect to each licensed product, would be reduced by up to an aggregate of $65.0 million upon the achievement of certain specified clinical and sales milestones. The Agensys Agreement will terminate upon the expiration of the last royalty term for the products covered by the Agensys Agreement, which is the earlier of (i) the date of expiration or abandonment of the last valid claim within the licensed patent rights covering any licensed products under the Agreement, (ii) the expiration of regulatory exclusivity as to a licensed product, and (iii) 10 years after the first commercial sale of a licensed product. Either party may terminate the Agensys Agreement upon a material breach by the other party that remains uncured following 60 days after the date of written notice of such breach (or 30 days if such material breach is related to failure to make payment of amounts due under the Agensys Agreement) or upon certain insolvency events. In addition, Agensys may terminate the Agensys Agreement immediately upon written notice to the Company if the Company or any of its affiliates or permitted sublicensees commences an interference proceeding or challenges the validity or enforceability of any of Agensys’ patent rights. License Agreement - BioVec On June 10, 2015, the Company and BioVec Pharma, Inc. (“BioVec”) entered into a license agreement (the “BioVec Agreement”) pursuant to which BioVec agreed to supply the Company with certain proprietary cell lines and granted to the Company a non-exclusive, worldwide license to certain of its patent rights and related know-how related to such proprietary cell lines. As consideration for the products supplied and rights granted to the Company under the BioVec Agreement, the Company agreed to pay to BioVec an upfront fee of $100,000 within ten business days of the effective date of the BioVec Agreement and a fee of $300,000 within ten business days of its receipt of the first release of GMP lot of the products licensed under the BioVec Agreement. In addition, the Company agreed to pay to BioVec an annual fee of $150,000, commencing 30 days following the first filing of an Investigational New Drug Application (an IND filing), or its foreign equivalent, for a product covered by the license; with such annual fees being creditable against any royalties payable by the Company to BioVec under the BioVec Agreement. The Company also is required to make a $250,000 milestone payment to BioVec for each of the first three licensed products to enter into a clinical phase trial and one-time milestone payments of $2.0 million upon receipt of a registration granted by the Federal Drug Administration or European Medicines Agency on each of the Company’s first three licensed products. The BioVec Agreement additionally provides that the Company will pay to BioVec a royalty in the low single digits on net sales of products covered by the BioVec Agreement. The Company may also grant sublicensees under the licensed patent rights and know-how to third parties for limited purposes related to the use, sale and other exploitation of the products licensed under the BioVec Agreement. The BioVec Agreement will continue until terminated. The BioVec Agreement may be terminated by the Company, in its sole discretion, at any time upon 90 days written notice to BioVec. Either party may terminate the BioVec Agreement in the event of a breach by the other party of any material provision of the BioVec Agreement that remains uncured on the date that is 60 days after written notice of such failure or upon certain insolvency events that remain uncured following the date that is 30 days after the date of written notice to a party regarding such insolvency event. Litigation Securities Litigation On May 29, 2020, the U.S. District Court for the Southern District of Texas, Houston Division granted the Company’s motion to dismiss with prejudice in the purported class action complaint filed on February 6, 2018 against the Company and certain of its current and former employees, captioned Nipun Kakkar v. Bellicum Pharmaceuticals, Inc., Rick Fair and Alan Musso. As previously reported, the complaint alleged that the Company and members of its management violated federal securities laws by making allegedly false and misleading statements. The court’s written order dismissed the case in its entirety with prejudice, resulting in a termination of all claims. The deadline for the plaintiffs to appeal has expired. On July 19, 2018, a purported shareholder derivative complaint captioned Seung Paik v. Richard A. Fair, et al. was filed against the Company’s directors and certain of the Company’s officers in the U.S. District Court for the Southern District of Texas, Houston Division. The lawsuit is based on the same facts as the Kakkar class action and purports to seek damages on behalf of the Company against the individual defendants for breach of fiduciary duty, waste, unjust enrichment and violations of Section 14(a) of the Exchange Act. The complaint alleges that the defendants caused or allowed the Company to disseminate misstatements regarding the clinical trials for rivo-cel and to make false or misleading statements in the proxy materials for the Company’s 2017 annual meeting of stockholders. On July 8, 2019, another purported shareholder derivative complaint captioned Scott Ludovissy and Ann Gordon Trammell v. Richard A. Fair, et al. was filed against the same defendants in the same court. On November 1, 2019, an additional purported shareholder derivative complaint captioned Mildred Taylor and Jessica Amor v. Richard A. Fair, et al. was filed against certain of the Company’s officers and directors in the District of Delaware. The lawsuit purports to seek monetary damages. The Taylor complaint includes substantially similar factual allegations as the other matters described above and seeks to hold the defendants liable for allegedly causing the Company to make material misstatements. The Paik, Ludovissy, and Taylor derivative causes of action have been stayed until reinstated on motion of the parties. Other Litigation On May 29, 2019, Bellicum was served with a second amended complaint indicating that the Company had been added as an additional defendant in an ongoing civil tort lawsuit, captioned Kelly v. Children’s Hospital of Los Angeles et al., filed in the Los Angeles County Superior Court, Case No. BC681477. On July 10, 2019, a third amended complaint was filed, which alleges claims for wrongful death, negligence, breach of fiduciary duty, fraud, medical battery on decedent, medical battery on individual plaintiffs, products liability - failure to warn, breach of express warranty and products liability design or manufacturing defect. Plaintiffs are seeking unspecified monetary damages including punitive damages. In response to the third amended complaint, Bellicum filed a demurrer and a motion to strike portions of the third amended complaint, the hearings for which have been continued indefinitely due to the COVID-19 pandemic. The Company intends to vigorously defend itself in these proceedings. An adverse finding could materially affect our business and results of operations.

ORGANIZATION, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying unaudited condensed financial statements have been prepared in conformity with the authoritative U.S. generally accepted accounting principles (“GAAP”) for interim financial information and pursuant to Form 10-Q and Article 10 of Regulation S-X of the Securities and Exchange Commission (SEC).
Use of Estimates	Use of Estimates The preparation of the interim condensed consolidated financial statements in accordance with GAAP requires management to make certain estimates and judgments that affect the reported amounts of assets, liabilities, and expenses. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition Cancer Research Grant Contract On August 9, 2017, the Company entered into a Cancer Research Grant Contract (the “CPRIT Agreement”) with the Cancer Prevention Research Institute of Texas (“CPRIT”), pursuant to which CPRIT awarded a grant of approximately $16.9 million to the Company to fund development of rivo-cel for hematologic cancer (the “CPRIT Award”). The CPRIT Award is contingent upon funds being available during the term of the CPRIT Agreement and subject to CPRIT’s ability to perform its obligations under the CPRIT Agreement. During 2017, the Company received $4.2 million in advance funding from CPRIT, which was recorded as deferred revenue. During the three and six month periods ended June 30, 2020, the Company did not incur expenses or recognize revenue for work performed under the CPRIT grant. During the three and six month periods ended June 30, 2019, the Company incurred expenses and recognized revenue of $1.4 million and $1.9 million, respectively, for work performed under the CPRIT grant. The CPRIT Agreement was due to expire on February 29, 2020, but was terminated early by the Company on January 31, 2020. Upon termination of the CPRIT Agreement, the Company reclassified the remaining unexpended award proceeds of $0.8 million from deferred revenue to accrued liabilities. During the three month period ended June 30, 2020, the Company returned the remaining unexpended award proceeds to CPRIT and released the accrued liability.
Cash and Cash Equivalents	Cash, Cash Equivalents and Restricted Cash The Company considers all short-term, highly liquid investments with maturity of three months or less from the date of purchase and that can be liquidated without prior notice or penalty, to be cash equivalents.
Warrant Derivatives	Warrant Derivatives Freestanding warrants are classified as liabilities in the accompanying consolidated balance sheets as they are exercisable for multiple underlying instruments that are potentially redeemable. The Company accounts for these warrants at fair value on the date of issuance and are subject to re-measurement to fair value at each balance sheet date. Any change in fair value is recognized as a component of other income (expense) on the accompanying consolidated statements of operations and comprehensive loss. The Company will continue to adjust the liability for changes in fair value until the earlier of the exercise or expiration of the warrants or a change in control, as defined. The warrants are freely exercisable at any time from the issuance date until the expiration date, provided exercise does not cause a warrant holder to exceed a pre-determined beneficial ownership limit. The Company estimates the fair value of these liabilities using the Black-Scholes valuation technique, which utilizes assumptions including (i) the fair value of the underlying stock at the valuation measurement date, (ii) volatility of the price of the underlying stock, (iii) the expected term, and (iv) risk-free interest rates.
Preferred Stock	Preferred Stock Preferred shares issued by the Company that are subject to mandatory redemption are classified as liability instruments in the accompanying condensed consolidated balance sheets and are measured at fair value at the date of issuance. Conditionally redeemable preferred shares (including preferred shares that feature redemption rights that are either within the control of the holder or subject to redemption upon the occurrence of uncertain events not solely within the Company’s control) are classified within mezzanine equity in the accompanying condensed consolidated balance sheets. At all other times, preferred shares are classified within stockholders’ (deficit) equity.
Operating Leases	Operating Leases At the inception of a contractual arrangement, the Company determines whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. If both criteria are met, upon lease commencement, the Company records a lease liability which represents the Company’s obligation to make lease payments arising from the lease, and a corresponding right-of-use (“ROU”) asset which represents the Company’s right to use an underlying asset during the lease term. Operating leases are recognized as ROU assets and operating lease liabilities on the balance sheet based on the present value of the future minimum lease payments over the lease term at commencement date calculated using the Company's incremental borrowing rate applicable to the underlying asset unless the implicit rate is readily determinable. Any lease incentives received are deferred and recorded as a reduction of the ROU asset and amortized over the term of the lease. Rent expense, comprised of amortization of the ROU asset and the implicit interest accreted on the operating lease liability, is recognized on a straight-line basis over the lease term. The Company determines the lease term as the non-cancellable period of the lease and may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise such options. Leases with a term of 12 months or less are not recognized on the balance sheets.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in an orderly transaction between market participants in a principal market on the measurement date. Accounting standards include disclosure requirements around fair values used for certain financial instruments and establish a fair value hierarchy. The three-tier hierarchy defines a three-tiered valuation hierarchy for disclosures that prioritizes valuation inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market, as described further in Note 2. Observable inputs reflect readily obtainable data from independent sources, and unobservable inputs reflect the Company’s market assumptions. These inputs are classified into the following hierarchy: Level 1 Inputs - quoted prices (unadjusted) in active markets for identical assets that the reporting entity has the ability to access at the measurement date; Level 2 Inputs - inputs other than quoted prices included within Level 1 that are observable for the asset, either directly or indirectly; and Level 3 Inputs - unobservable inputs for the assets. The categorization of a financial instrument within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company believes the recorded values of its financial instruments, including cash and cash equivalents, accounts payable, accrued liabilities, and debt approximate their fair values due to the short-term nature of these instruments.
Financial Instruments and Credit Risks	Financial Instruments and Credit Risks Financial instruments that potentially subject the Company to credit risk include cash and cash equivalents and accounts receivable. Cash is deposited in demand accounts in federally insured domestic institutions to minimize risk. Insurance is provided through the Federal Deposit Insurance Corporation and Security Investor Protection Corporation. Although the balances in these accounts exceed the federally insured limit from time to time, the Company has not incurred losses related to these deposits.
Equity Issuance Costs	Equity Issuance Costs Equity issuance costs represent costs paid to third parties in order to obtain equity financing. The costs related to preferred and common stock have been netted against the proceeds of the equity issuances.
Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders	Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period without consideration for common stock equivalents. Diluted earnings per share is based on the treasury stock method and includes the effect from potential issuance of ordinary shares, such as shares issuable pursuant to the conversion of preferred stock to common stock, exercise of warrants to purchase common stock, exercise of stock options, and vesting of restricted stock units.
Application of New Accounting Standards	New Accounting Requirements and Disclosures Fair Value Measurement In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement, which modifies fair value disclosures and removes some disclosure requirements for both public and private companies. In addition, public companies are subject to some new disclosure requirements which requires to disclose the changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements. ASU No. 2018-13 is effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. The Company adopted the standard effective January 1, 2020 with no material effect on its financial statements. Financial Instruments – Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires the measurement of all expected credit losses for financial assets including trade receivables held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. ASU No. 2016-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The Company adopted the standard effective January 1, 2020 with no material effect on its financial statements. Subsequent to the issuance of ASU 2016-13, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses. This ASU does not change the core principle of the guidance in ASU 2016-13, instead these amendments are intended to clarify and improve operability of certain topics included within the credit losses guidance. The FASB also subsequently issued ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Derivatives and Hedging (Topic 815), and Financial Instruments (Topic 842), which did not change the core principle of the guidance in ASU 2016-13 but clarified that expected recoveries of amounts previously written off and expected to be written off should be included in the valuation account and should not exceed amounts previously written off and expected to be written off. The guidance is effective for fiscal years, and interim periods within those years, beginning after December 15, 2019 for public business entities, excluding smaller reporting companies. Early adoption is permitted. As a smaller reporting company, the guidance will be effective for the Company during the first quarter of 2023. The Company is in the process of assessing the impact adoption will have on its consolidated financial statements. Income Taxes In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (Topic 740). The guidance eliminates certain exceptions for recognizing deferred taxes for investments, performing intraperiod allocation and calculating income taxes in interim periods. This guidance also includes guidance to reduce complexity in certain areas, including recognizing deferred taxes for tax goodwill and allocating taxes to members of a consolidated group. ASU 2019-12 is effective for annual and interim periods in fiscal years beginning after December 15, 2020. Early adoption is permitted. The Company is currently evaluating the impact this change will have on its consolidated financial statements. Investments In January 2020, the FASB issued Accounting Standards Update No. 2020-01, Investments—Equity Securities (Topic 321), Investments—Equity Method and Joint Ventures (Topic 323), and Derivatives and Hedging (Topic 815)—Clarifying the Interactions between Topic 321, Topic 323, and Topic 815 (a consensus of the Emerging Issues Task Force), which clarifies the interaction of the accounting for equity securities, investments accounted for under the equity method, and certain forward contracts and purchased options. This update is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years, and early adoption is permitted. The Company is in the process of determining the impact the adoption will have on its consolidated financial statements as well as whether to early adopt the new guidance

ORGANIZATION, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

6 Months Ended

Jun. 30, 2020

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Cash, Cash Equivalents and Restricted Cash, Reconciliation


(in thousands)	June 30, 2020		December 31, 2019
Cash and cash equivalents	$	66,408	$	91,028
Restricted cash, current	87		2,788
Restricted cash, non-current	1,500		—
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$	67,995	$	93,816

Accrued Expenses and Other Liabilities

Accrued expenses and other liabilities consist of the following:


(in thousands)	June 30, 2020		December 31, 2019
Accrued payroll	$	2,104	$	2,032
Accrued patient treatment costs	954		1,162
Accrued manufacturing costs	273		2,230
Accrued professional services	639		654
Accrued obligations under material supply agreements	1,123		1,121
Accrued other	2,015		2,571
Total accrued expenses and other current liabilities	$	7,108	$	9,770

Earnings Per Share, Potentially Dilutive Securities


	June 30, 2020	June 30, 2019
Common Stock Equivalents:	Number of Shares
Redeemable convertible series 1 preferred stock	5,340,000	—
Warrants to purchase common stock	5,750,000	—
Private placement option	9,675,000	—
Options to purchase common stock	1,122,938	766,533
Unvested shares of restricted stock units	187,705	21,593
Total common stock equivalents	22,075,643	788,126

FAIR VALUE MEASUREMENTS AND INVESTMENT SECURITIES (Tables)

6 Months Ended

Jun. 30, 2020

Fair Value Disclosures [Abstract]

Summary of Assets Measured at Fair Value on a Recurring Basis


	Fair Value at June 30, 2020										Fair Value at December 31, 2019
(in thousands)	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds and treasury bills	$	55,253	$	—	$	—	$	77,170	$	—	$	—
Total cash equivalents	$	55,253	$	—	$	—	$	77,170	$	—	$	—

Schedule of Derivative Liabilities at Fair Value

The fair value of the warrants has been estimated with the following weighted-average assumptions:


	June 30, 2020		December 31, 2019
Risk-free interest rate	0.41	%	1.83	%
Volatility of underlying stock price	90.00	%	78.67	%
Expected term (years)	6.14		6.64

The fair value of the private placement option has been estimated with the following weighted-average assumptions:


	June 30, 2020
Risk-free interest rate	0.59	%
Volatility of underlying stock price	90.00	%
Expected term (years)	7.00

The following table provides the warrant derivative and private placement option reported at fair value and measured on a recurring basis:


	Fair Value at June 30, 2020										Fair Value at December 31, 2019
(in thousands)	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Warrant derivative liability	$	—	$	—	$	28,183	$	—	$	—	$	52,184
Private placement option liability	—		—		33,970		—		—		12,094
Total fair value	$	—	$	—	$	62,153	$	—	$	—	$	64,278

The following table reflects the fair value roll forward reconciliation of the warrant derivative and private placement option liabilities for the period ended June 30, 2020:


(in thousands)	Warrant Derivative Liability		Private Placement Option Liability		Total
Balance, December 31, 2019	$	52,184	$	12,094	$	64,278
Change in fair value	(24,001)		21,876		(2,125)
Balance, June 30, 2020	$	28,183	$	33,970	$	62,153

LEASES (Tables)

6 Months Ended

Jun. 30, 2020

Leases [Abstract]

Components of Lease Cost

Components of lease cost are as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
(in thousands)	2020		2019		2020		2019
Finance lease cost:
Amortization of leased asset	$	18	$	18	$	36	$	24
Interest on lease liabilities	6		7		12		10
Operating lease cost	194		547		499		993
Short-term lease cost	207		12		241		47
Total lease cost	$	425	$	584	$	788	$	1,074


	June 30, 2020
Weighted-average remaining lease term:
Operating leases	2.10 years
Finance leases	1.90 years
Weighted-average discount rate:
Operating leases	12.77	%
Finance leases	13.28	%

Supplemental cash flow information and non-cash activity related to the Company's operating leases are as follows:


	Six Months Ended June 30,
(in thousands)	2020				2019
Operating cash flow information:
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases			$	819			$	1,095
Operating cash flows from finance leases	12				10
Financing cash flows from finance leases	35				14
Non-cash activity:
Right-of-use assets obtained in exchange for lease obligations	$	—			$	1,259

Maturities of lease liabilities by year for leases are as follows:

Maturity of Finance Lease Liabilities


(in thousands)	Operating Leases		Financing Leases
2020	$	252	$	48
2021	515		90
2022	316		39
2023 and beyond	—		—
Total lease payments	1,083		177
Less: Imputed interest	(139)		(21)
Present value of lease liabilities	$	944	$	156

Maturity of Operating Lease Liabilities


(in thousands)	Operating Leases		Financing Leases
2020	$	252	$	48
2021	515		90
2022	316		39
2023 and beyond	—		—
Total lease payments	1,083		177
Less: Imputed interest	(139)		(21)
Present value of lease liabilities	$	944	$	156

AUGUST 2019 PUBLIC OFFERING AND PRIVATE PLACEMENT (Tables)

6 Months Ended

Jun. 30, 2020

Statement of Stockholders' Equity [Abstract]

Schedule of Derivative Liabilities at Fair Value

The fair value of the warrants has been estimated with the following weighted-average assumptions:


	June 30, 2020		December 31, 2019
Risk-free interest rate	0.41	%	1.83	%
Volatility of underlying stock price	90.00	%	78.67	%
Expected term (years)	6.14		6.64

The fair value of the private placement option has been estimated with the following weighted-average assumptions:


	June 30, 2020
Risk-free interest rate	0.59	%
Volatility of underlying stock price	90.00	%
Expected term (years)	7.00

The following table provides the warrant derivative and private placement option reported at fair value and measured on a recurring basis:


	Fair Value at June 30, 2020										Fair Value at December 31, 2019
(in thousands)	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
Warrant derivative liability	$	—	$	—	$	28,183	$	—	$	—	$	52,184
Private placement option liability	—		—		33,970		—		—		12,094
Total fair value	$	—	$	—	$	62,153	$	—	$	—	$	64,278

The following table reflects the fair value roll forward reconciliation of the warrant derivative and private placement option liabilities for the period ended June 30, 2020:


(in thousands)	Warrant Derivative Liability		Private Placement Option Liability		Total
Balance, December 31, 2019	$	52,184	$	12,094	$	64,278
Change in fair value	(24,001)		21,876		(2,125)
Balance, June 30, 2020	$	28,183	$	33,970	$	62,153

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

Stock Option Activity

The following table summarizes the stock option activity for all stock plans during the six months ended June 30, 2020:


			Options and Inducement Awards
Outstanding at December 31, 2019			567,842
Granted			634,085
Exercised			—
Forfeited			(78,989)
Outstanding at June 30, 2020			1,122,938
Exercisable at June 30, 2020			335,278

Stock Award Activity For All Stock Plans

The following table summarizes the stock award activity for all stock plans during the six months ended June 30, 2020:


			Restricted Stock Awards and Units
Outstanding at December 31, 2019			6,359
Granted			207,547
Vested			(2,309)
Forfeited			(23,892)
Outstanding at June 30, 2020			187,705

ESPP Activity

A summary of activity within the ESPP follows:


	Six Months Ended June 30,
(in thousands)	2020		2019
Deductions from employees	$	62	$	48
Share-based compensation expense recognized	46		57
Remaining share-based compensation expense	144		135

Valuation Assumptions

The fair value of option grants is determined using the Black-Scholes option-pricing model and has been estimated with the following weighted-average assumptions:


	Six Months Ended June 30,
	2020		2019
Risk-free interest rate	1.24	%	2.25	%
Volatility	81.53	%	72.10	%
Expected life (years)	6.04		6.08
Expected dividend yield	—		—

Share-Based Compensation Expense by Classification

Share-based compensation expense by classification for the three and six months ended June 30, 2020 and 2019 are as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
(in thousands)	2020		2019		2020		2019
Research and development	$	661	$	959	$	1,209	$	2,024
General and administrative	903		1,037		1,678		2,108
Total	$	1,564	$	1,996	$	2,887	$	4,132

ORGANIZATION, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)			3 Months Ended		6 Months Ended
	Apr. 14, 2020 USD ($)	Feb. 05, 2020 shares	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) shares	Jun. 30, 2019 USD ($)	Jun. 15, 2020 shares	Jun. 14, 2020 shares	Feb. 04, 2020 shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2017 USD ($)	Aug. 09, 2017 USD ($)
Class of Stock [Line Items]
Reverse stock split ratio		0.1
Common stock, authorized (in shares) \| shares		40,000,000	80,000,000		80,000,000		80,000,000	40,000,000	200,000,000	80,000,000
Accumulated deficit			$ (558,643,000)		$ (558,643,000)					$ (533,025,000)
Revenues			0	$ 1,391,000	0	$ 1,907,000
Accrued expenses and other current liabilities			7,108,000		7,108,000					$ 9,770,000
Gain on dispositions, net			3,761,000	0	3,761,000	0
Grant from CPRIT
Class of Stock [Line Items]
Restricted cash, noncurrent			100,000		100,000						$ 4,200,000
Release Of Restricted Cash					(3,300,000)
Held in escrow
Class of Stock [Line Items]
Restricted cash, noncurrent			1,100,000		1,100,000
2130 W. Holcombe Blvd.
Class of Stock [Line Items]
Escrow Deposits Related to Property Sales	$ 1,500,000
Amount paid upon closing of asset sale	$ 15,000,000.0
Disposal Group, Held-for-sale, Not Discontinued Operations
Class of Stock [Line Items]
Assets held for sale, property and equipment			12,000,000.0		12,000,000.0
Assets held for sale, right-of-use assets			4,800,000		4,800,000
Assets held for sale, current lease liabilities			1,400,000		1,400,000
Assets held for sale, long-term lease liabilities			4,600,000		4,600,000
Gain on dispositions, net			3,800,000		3,800,000
Grants
Class of Stock [Line Items]
Revenues			0	$ 1,391,000	0	$ 1,907,000
CPRIT
Class of Stock [Line Items]
Grants awarded												$ 16,900,000
Advanced funding											$ 4,200,000
CPRIT \| Grants
Class of Stock [Line Items]
Revenues			0		0
Accrued expenses and other current liabilities			$ 800,000		$ 800,000

ORGANIZATION, BASIS OF PRESENTATION, AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Cash Reconciliation (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 66,408	$ 91,028
Restricted cash, current	87	2,788
Restricted cash, non-current	1,500	0
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$ 67,995	$ 93,816	$ 46,841	$ 48,668

ORGANIZATION, BASIS OF PRESENTATION, AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accrued Expenses and Other Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll	$ 2,104	$ 2,032
Accrued patient treatment costs	954	1,162
Accrued manufacturing costs	273	2,230
Accrued professional services	639	654
Accrued obligations under material supply agreements	1,123	1,121
Accrued other	2,015	2,571
Total accrued expenses and other current liabilities	$ 7,108	$ 9,770

ORGANIZATION, BASIS OF PRESENTATION, AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Earnings Per Share, Potentially Dilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total common stock equivalents (in shares)	22,075,643	788,126
Redeemable convertible series 1 preferred stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total common stock equivalents (in shares)	5,340,000	0
Warrants to purchase common stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total common stock equivalents (in shares)	5,750,000	0
Private placement option
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total common stock equivalents (in shares)	9,675,000	0
Options to purchase common stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total common stock equivalents (in shares)	1,122,938	766,533
Unvested shares of restricted stock units
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total common stock equivalents (in shares)	187,705	21,593

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Assets Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Restricted cash, non-current	$ 1,500	$ 0
Level 1
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total cash equivalents	55,253	77,170
Level 1 \| Money market funds and treasury bills
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total cash equivalents	55,253	77,170
Level 2
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total cash equivalents	0	0
Level 2 \| Money market funds and treasury bills
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total cash equivalents	0	0
Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total cash equivalents	0	0
Level 3 \| Money market funds and treasury bills
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total cash equivalents	$ 0	$ 0

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Fair Value of Warrants (Details)	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivative [Line Items]
Risk-free interest rate	1.24%	2.25%
Volatility of underlying stock price	81.53%	72.10%
Expected life (years)	6 years 14 days	6 years 29 days
Warrant Derivative Liability
Derivative [Line Items]
Risk-free interest rate	0.41%		1.83%
Volatility of underlying stock price	90.00%		78.67%
Expected life (years)	6 years 1 month 20 days		6 years 7 months 20 days
Private Placement Option Liability
Derivative [Line Items]
Risk-free interest rate	0.59%
Volatility of underlying stock price	90.00%
Expected life (years)	7 years

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Derivative Liabilities Reported at Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	$ 28,183	$ 52,184
Private placement option derivative liability	33,970	12,094
Level 1
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	0	0
Private placement option derivative liability	0	0
Total derivative liabilities	0	0
Level 2
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	0	0
Private placement option derivative liability	0	0
Total derivative liabilities	0	0
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warrant derivative liability	28,183	52,184
Private placement option derivative liability	33,970	12,094
Total derivative liabilities	$ 62,153	$ 64,278

LEASES - Additional Information (Details)	Jun. 30, 2020
Leases [Abstract]
Remaining lease term	2 years

LEASES - Components of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Finance lease cost:
Amortization of leased asset	$ 18	$ 18	$ 36	$ 24
Interest on lease liabilities	6	7	12	10
Operating lease cost	194	547	499	993
Short-term lease cost	207	12	241	47
Total lease cost	$ 425	$ 584	$ 788	$ 1,074
Weighted-average remaining lease term, operating leases	2 years 1 month 6 days		2 years 1 month 6 days
Weighted-average remaining lease term, finance leases	1 year 10 months 24 days		1 year 10 months 24 days
Weighted-average discount rate, operating leases	12.77%		12.77%
Weighted-average discount rate, finance leases	13.28%		13.28%

LEASES - Supplemental Cash Flow Information Related to Operating Leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating cash flow information:
Operating cash flows from operating leases	$ 819	$ 1,095
Operating cash flows from operating leases	12	10
Financing cash flows from finance leases	35	14
Right-of-use assets obtained in exchange for lease obligations	$ 0	$ 1,259

LEASES - Weighted Average Remaining Lease Term and Discount Rate (Details)	Jun. 30, 2020
Leases [Abstract]
Weighted-average remaining lease term, operating leases	2 years 1 month 6 days
Weighted-average discount rate, operating leases	12.77%

LEASES - Maturity of Lease Liabilities (Details)	Jun. 30, 2020 USD ($)
Operating Leases
2020	$ 252,000
2021	515,000
2022	316,000
2023 and beyond	0
Total lease payments	1,083,000
Less: Imputed interest	(139,000)
Present value of lease liabilities	944,000
Financing Leases
2020	48,000
2021	90,000
2022	39,000
2023 and beyond	0
Total lease payments	177,000
Less: Imputed interest	(21,000)
Present value of lease liabilities	$ 156,000

DEBT (Details)			3 Months Ended		6 Months Ended
DEBT (Details)	Apr. 14, 2020 USD ($)	Dec. 21, 2017 USD ($) installment	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
Line of Credit Facility [Line Items]
Payment on debt					$ 10,000,000	$ 0
Amortization of deferred issuance costs					388,000	439,000
Oxford Loan
Line of Credit Facility [Line Items]
Borrowings		$ 35,000,000.0
Number of periodic payments \| installment		35
Final payment, percent of principal		8.70%
Early repayment fee, percentage of prepaid amount, period one		3.00%
Early repayment fee, percentage of prepaid amount, period two		2.00%
Early repayment fee, percentage of prepaid amount, period three		1.00%
Payment on debt	$ 7,000,000.0
Partial payment of final payment percentage	$ 600,000
Payment of debt issuance costs		$ 100,000
Final facility charge payment		$ 3,000,000.0
Amortization of deferred issuance costs			$ 200,000	$ 200,000	$ 400,000	$ 400,000
Interest rate at end of period			10.98%		10.98%
Oxford Loan \| Floating per Annum Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate - plus (minus)		7.25%
Oxford Loan \| London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate - plus (minus)		1.25%
Hercules Loan
Line of Credit Facility [Line Items]
Payment on debt		$ 32,900,000

AUGUST 2019 PUBLIC OFFERING AND PRIVATE PLACEMENT - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		6 Months Ended
	Aug. 16, 2019	Jun. 30, 2020
Class of Stock [Line Items]
Proceeds from issuance of redeemable convertible preferred stock in a public offering, net		$ 53.8
Proceeds upon entering into private placement agreement		11.2
Total offering costs related to warrants and options		$ 3.0
Series 1 redeemable convertible non-voting preferred stock
Class of Stock [Line Items]
Shares issuable per warrants (in shares)		10
Public Offering
Class of Stock [Line Items]
Shares issuable under warrants (in shares)	5,750,000
Price per share (in dollars per share)	$ 100.00
Public Offering \| Series 1 redeemable convertible non-voting preferred stock
Class of Stock [Line Items]
Number of shares of common stock sold in offering (in shares)	575,000
Warrants exercise price (in dollars per share)	$ 130.00
Public Offering \| Common Stock
Class of Stock [Line Items]
Shares issuable per warrants (in shares)	10
Warrants exercise price (in dollars per share)	$ 13.00
Public Offering \| Common Stock \| Minimum
Class of Stock [Line Items]
Warrants, limitations on ownership after exercise		9.99%
Public Offering \| Common Stock \| Maximum
Class of Stock [Line Items]
Warrants, limitations on ownership after exercise		19.99%
Private Placement \| Series 2 Preferred Stock
Class of Stock [Line Items]
Number of shares of common stock sold in offering (in shares)	350,000
Shares issuable under warrants (in shares)	2,800,000
Price per share (in dollars per share)	$ 100.00
Warrants exercise price (in dollars per share)	$ 10.00
Private Placement \| Series 3 Preferred Stock
Class of Stock [Line Items]
Number of shares of common stock sold in offering (in shares)	250,000
Private Placement \| Preferred Stock
Class of Stock [Line Items]
Shares issuable under warrants (in shares)	875,000
Price per share (in dollars per share)	$ 140.00
Warrants exercise price (in dollars per share)	$ 14.00

AUGUST 2019 PUBLIC OFFERING AND PRIVATE PLACEMENT - Fair Value of Derivative Liability (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Change in fair value of warrant and private placement option liabilities	$ 30,701	$ 0	$ (2,125)	$ 0
Level 3
Derivatives, Fair Value [Line Items]
Derivative liability, fair value at date of issuance	62,153		62,153		$ 64,278
Change in fair value of warrant and private placement option liabilities			(2,125)
Warrant Derivative Liability \| Level 3
Derivatives, Fair Value [Line Items]
Derivative liability, fair value at date of issuance	28,183		28,183		52,184
Change in fair value of warrant and private placement option liabilities			(24,001)
Private Placement Option Liability \| Level 3
Derivatives, Fair Value [Line Items]
Derivative liability, fair value at date of issuance	$ 33,970		33,970		$ 12,094
Change in fair value of warrant and private placement option liabilities			$ 21,876

REDEEMABLE CONVERTIBLE PREFERRED STOCK (Details) - $ / shares	Aug. 16, 2019	Jun. 30, 2020	Aug. 31, 2019
Class of Stock [Line Items]
Preferred stock, authorized (in shares)			10,000,000
Preferred stock, par value (in dollars per share)			$ 0.01
50-day trading volume on Nasdaq stock market (in shares)		50,000
Series 1 redeemable convertible non-voting preferred stock
Class of Stock [Line Items]
Preferred stock, authorized (in shares)			1,517,500
Preferred stock, outstanding (in shares)		534,000
Shares issuable per warrants (in shares)		10
Series 2 Preferred Stock \| Private Placement
Class of Stock [Line Items]
Number of shares of common stock sold in offering (in shares)	350,000
Price per share (in dollars per share)	$ 100.00
Series 3 Preferred Stock
Class of Stock [Line Items]
Closing price of common stock (in usd per share)		$ 35.00
Series 3 Preferred Stock \| Private Placement
Class of Stock [Line Items]
Number of shares of common stock sold in offering (in shares)	250,000
Series 1 and 2 Preferred Stock
Class of Stock [Line Items]
Price per share (in dollars per share)		100.00
Closing price of common stock (in usd per share)		$ 25.00
Preferred Stock \| Private Placement
Class of Stock [Line Items]
Price per share (in dollars per share)	$ 140.00

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS - Additional Information (Details) $ in Millions		1 Months Ended		6 Months Ended		12 Months Ended
	Oct. 05, 2018 USD ($)	Jun. 30, 2020 USD ($) shares	Jan. 31, 2020 shares	Jun. 30, 2020 USD ($) plan shares	Jun. 30, 2019 shares	Dec. 31, 2019 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, issued (in shares)		5,127,525		5,127,525		5,076,593
Number of share-based compensation plans \| plan				5
Compensation cost not yet recognized \| $		$ 9.4		$ 9.4
Period for recognition				2 years 3 months 18 days
2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		250,000		250,000
Additional authorized shares approved (in shares)		500,000	600,000
2019 Equity Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			600,540
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)				4 years
Expiration period (in years)				10 years
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount rate from grant date fair market value				15.00%
Issuance of common stock - Employee Stock Purchase Plan (in shares)				9,526	4,000
Shares available for issuance under ESPP (in shares)		23,937		23,937
ESPP \| 2014 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		55,000		55,000
Jefferies LLC
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of stock from employee stock purchase plan \| $	$ 60.0					$ 9.0
Common stock, issued (in shares)						259,115

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS - Stock Option Activity (Details) - Employee Stock Options And Inducement Option Awards	6 Months Ended
	Jun. 30, 2020 shares
Options and Inducement awards
Outstanding at beginning of period (in shares)	567,842
Granted (in shares)	634,085
Exercised (in shares)	0
Forfeited (in shares)	(78,989)
Outstanding at end of period (in shares)	1,122,938
Exercisable (in shares)	335,278

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS - Stock Award Activity For All Stock Plans (Details) - Restricted Stock Awards and Units	6 Months Ended
	Jun. 30, 2020 shares
Restricted Stock Awards and Units
Beginning balance (in shares)	6,359
Granted (in shares)	207,547
Vested (in shares)	(2,309)
Forfeited (in shares)	(23,892)
Ending balance (in shares)	187,705

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS - ESPP Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	$ 1,564	$ 1,996	$ 2,887	$ 4,132
Remaining share-based compensation expense			2,887	4,132
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deductions from employees			62	48
Share-based compensation expense recognized			46	57
Remaining share-based compensation expense			$ 144	$ 135

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS - Valuation Assumptions (Details)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Share-based Payment Arrangement [Abstract]
Risk-free interest rate	1.24%	2.25%
Volatility	81.53%	72.10%
Expected life (years)	6 years 14 days	6 years 29 days
Expected dividend yield	0.00%	0.00%

STOCKHOLDERS' EQUITY AND SHARE-BASED COMPENSATION PLANS - Expense by Classification (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	$ 1,564	$ 1,996	$ 2,887	$ 4,132
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	661	959	1,209	2,024
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense recognized	$ 903	$ 1,037	$ 1,678	$ 2,108

COMMITMENTS AND CONTINGENCIES (Details) - Licensing Agreements			1 Months Ended
	Dec. 10, 2015 USD ($)	Jun. 10, 2015 USD ($) product	Mar. 31, 2016 USD ($)
Baylor
Loss Contingencies [Line Items]
Nonrefundable license fee			$ 100,000
Agensys, Inc.
Loss Contingencies [Line Items]
Nonrefundable upfront fee	$ 3,000,000.0
Milestone payments upon first achievement of specified clinical milestones	5,000,000.0
Milestone payments upon achievement of specified clinical milestones for each licensed product	50,000,000.0
Milestone payments upon achievement of sales milestones	75,000,000.0
Option exercise fee	5,000,000.0
Milestone payments reduced upon exercise of option	$ 65,000,000.0
Termination period, number of years after first commercial sale of licensed product	10 years
Termination period, notice of failure on uncured items	60 days
Period of notice of failure on uncured items, if material breach is related to failure to make payments	30 days
BioVec Pharma Inc
Loss Contingencies [Line Items]
Nonrefundable upfront fee		$ 100,000
Milestone payments upon first achievement of specified clinical milestones		$ 250,000
Termination period, notice of failure on uncured items		60 days
Upfront fee payment period, number of days from effective date		10 days
License costs due upon first release of product		$ 300,000
License costs due upon first release of product, period of payment		10 days
License agreement, annual fee		$ 150,000
License agreement, annual fee period, from first IND filing		30 days
Milestone payments, number of initial products \| product		3
License agreement, milestone payments upon receipt of FDA or EMA registration		$ 2,000,000.0
Termination notice period for any other breach		90 days
Termination period, after insolvency event		30 days