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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	May 08, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Entity Registrant Name	UNUM THERAPEUTICS INC.
Entity Central Index Key	0001622229
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		31,161,941
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity File Number	001-38443
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5308248
Entity Address, Address Line One	200 Cambridge Park Drive
Entity Address, Address Line Two	Suite 3100
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02140
City Area Code	(617)
Local Phone Number	945-5576
Title of 12(b) Security	Common Stock, $0.001 Par Value
Trading Symbol	UMRX
Security Exchange Name	NASDAQ

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 29,604	$ 37,424
Accounts receivable		2,000
Prepaid expenses and other current assets	1,581	1,167
Total current assets	31,185	40,591
Operating lease, right-of-use asset	4,929	5,285
Property and equipment, net	1,570	1,865
Restricted cash	1,255	1,255
Other assets		427
Total assets	38,939	49,423
Current liabilities:
Accounts payable	628	3,183
Accrued expenses and other current liabilities	6,123	7,131
Operating lease liability	1,658	1,619
Deferred revenue	841	1,315
Total current liabilities	9,250	13,248
Operating lease liability, net of current portion	3,987	4,413
Total liabilities	13,237	17,661
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 150,000,000 shares authorized; 30,821,892 shares and 30,663,054 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	31	30
Additional paid-in capital	155,657	155,624
Accumulated deficit	(129,986)	(123,892)
Total stockholders’ equity	25,702	31,762
Total liabilities and stockholders' equity	$ 38,939	$ 49,423

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, Par value	$ 0.001	$ 0.001
Common stock, Shares authorized	150,000,000	150,000,000
Common stock, Shares issued	30,821,892	30,663,054
Common stock, Shares outstanding	30,821,892	30,663,054

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Collaboration revenue	$ 7,031	$ 3,053
Operating expenses:
Research and development	9,498	12,403
General and administrative	3,674	2,491
Total operating expenses	13,172	14,894
Loss from operations	(6,141)	(11,841)
Other income (expense):
Interest income	47	150
Total other income (expense), net	47	150
Net loss	$ (6,094)	$ (11,691)
Net loss per common share, basic and diluted	$ (0.20)	$ (0.39)
Weighted average common shares outstanding, basic and diluted	30,136,749	30,083,006
Comprehensive loss:
Net loss	$ (6,094)	$ (11,691)
Other comprehensive income (loss):
Unrealized gains on marketable securities, net of tax of $0		10
Total other comprehensive income		10
Comprehensive loss	$ (6,094)	$ (11,681)

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Unrealized gains (losses) on marketable securities, tax	$ 0	$ 0

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balances at Dec. 31, 2018	$ 60,234	$ 30	$ 152,275	$ (92,059)	$ (12)
Beginning Balances, Shares at Dec. 31, 2018		30,057,970
Issuance of common stock upon exercise of stock options	11		11
Issuance of common stock upon exercise of stock options, Shares		60,852
Stock-based compensation expense	726		726
Unrealized gains on marketable securities	10				10
Net loss	(11,691)			(11,691)
Ending Balances at Mar. 31, 2019	49,290	$ 30	153,012	(103,750)	$ (2)
Ending Balances, Shares at Mar. 31, 2019		30,118,822
Beginning Balances at Dec. 31, 2019	31,762	$ 30	155,624	(123,892)
Beginning Balances, Shares at Dec. 31, 2019		30,663,054
Issuance of common stock upon exercise of stock options	38	$ 1	37
Issuance of common stock upon exercise of stock options, Shares		207,292
Issuance of common stock under Employee Stock Purchase Plan	35		35
Issuance of common stock under Employee Stock Purchase Plan, shares		57,011
Issuance of common stock, net of issuance costs	262	$ 1	261
Issuance of common stock, net of issuance costs		726,382
Acquisition and retirement of treasury stock	(808)	$ (1)	(807)
Acquisition and retirement of treasury stock, shares		(831,847)
Stock-based compensation expense	507		507
Net loss	(6,094)			(6,094)
Ending Balances at Mar. 31, 2020	$ 25,702	$ 31	$ 155,657	$ (129,986)
Ending Balances, Shares at Mar. 31, 2020		30,821,892

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (6,094)	$ (11,691)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	295	330
Stock-based compensation expense	769	726
Realized loss on sales of marketable securities		1
Noncash consideration received from a customer	(808)
Net amortization (accretion) of premiums (discounts) on marketable securities		(49)
Changes in operating assets and liabilities:
Accounts receivable	2,000	(372)
Prepaid expenses and other current assets	(414)	(17)
Operating lease, right-of-use asset	356	334
Other assets	427	(427)
Accounts payable	(2,555)	317
Accrued expenses and other current liabilities	(1,008)	696
Operating lease liability	(387)	(352)
Deferred revenue	(474)	(1,014)
Net cash used in operating activities	(7,893)	(11,518)
Cash flows from investing activities:
Purchases of property and equipment		(42)
Proceeds from maturities and sales of marketable securities		14,992
Net cash provided by investing activities		14,950
Cash flows from financing activities:
Proceeds from issuance of common stock upon stock option exercises	38	11
Proceeds from issuance of stock from employee stock purchase plan	35
Net cash provided by financing activities	73	11
Net (decrease) increase in cash, cash equivalents and restricted cash	(7,820)	3,443
Cash, cash equivalents and restricted cash at beginning of period	38,679	56,926
Cash, cash equivalents and restricted cash at end of period	$ 30,859	$ 60,369

Nature of the Business and Basis of Presentation

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Unum Therapeutics, Inc. (“Unum” or “the Company”) is a biopharmaceutical company focused on developing curative cell therapies for solid tumors. Unum’s novel proprietary technology includes Bolt-On Chimeric Receptor (BOXR), designed to improve the functionality of engineered T cells by incorporating a “bolt-on” transgene to overcome resistance of the solid tumor microenvironment (TME) to T cell attack. Unum was incorporated in March 2014 under the laws of the State of Delaware.

Unum also developed product candidates using its novel proprietary technology, Antibody-Coupled T cell Receptor (ACTR), an autologous engineered T-cell therapy that combines the cell-killing ability of T cells and the tumor-targeting ability of co-administered antibodies to exert potent antitumor immune responses. In March 2020, the Company announced a strategic restructuring plan to shift away from ACTR, and prioritize its resources towards advancing its preclinical program, BOXR1030, for the treatment of solid tumor cancers.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

On April 1, 2019, the Company filed a shelf registration statement on Form S-3 with the SEC. The shelf registration statement allows the Company to sell from time-to-time up to $150 million of common stock, preferred stock, debt securities, warrants, or units comprised of any combination of these securities, for its own account in one or more offerings. The terms of any offering under the shelf registration statement will be established at the time of such offering and will be described in a prospectus supplement filed with the SEC prior to the completion of any such offering.

Additionally, on April 1, 2019 and pursuant to the Form S-3, the Company entered into a Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”), pursuant to which the Company may issue and sell, from time to time, shares of its common stock having an aggregate offering price of up to $50.0 million through Cowen as the sales agent. As of March 31, 2020, no shares have been sold under this Sales Agreement.

As announced on March 2, 2020, the Company initiated a reduction in force that resulted in the termination of approximately 60% of the Company’s employee workforce, or 43 employees. These reductions were substantially completed by the end of first quarter of 2020. The reduction in force was approved in connection with the Company’s restructuring plans to prioritize resources towards advancing its preclinical program, BOXR1030, for the treatment of solid tumor cancers.

On March 19, 2020, the Company entered into a Purchase Agreement with Lincoln Park Capital Fund, LLC (“LPC”), pursuant to which the Company may elect to sell to LPC up to $25,000,000 in shares of its Common Stock, subject to certain limitations and conditions set forth in the Purchase Agreement. Pursuant to the Purchase Agreement, the Company issued 726,382 shares of Common Stock to LPC as a commitment fee.

On March 26, 2020, the Company announced that we would be exploring strategic alternatives in order to maximize stockholder value and that the Company had engaged Ladenburg Thalmann & Co. Inc. to act as its strategic financial advisor to assist in the strategic review process. Despite undertaking this process, the Company may not be successful in completing a transaction, and, even if a strategic transaction is completed, it ultimately may not deliver the anticipated benefits or enhance stockholder value.

In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued.

On December 31, 2019, the Company received a deficiency letter from the Listing Qualifications Department of the Nasdaq Stock Market notifying it that, for the last 30 consecutive business days, the bid price for the Company’s common stock had closed below the minimum $1.00 per share requirement for continued inclusion on the Nasdaq Global Select Market (“Minimum Bid Price Requirement”). In accordance with Nasdaq Listing Rules, the Company had an initial period of 180 calendar days to regain compliance with the minimum bid price rule, which has been tolled as of April 16, 2020 and will restart on July 1, 2020. If the Company does not regain compliance with the Minimum Bid Price Requirement by September 11, 2020, then, under Nasdaq Listing Rules, the Company may transfer to The Nasdaq Capital Market, provided that it meets the continued listing requirement for the market value of publicly held shares and all other initial listing standards for The Nasdaq Capital Market, except for the Minimum Bid Price Requirement, and the Company would need to provide written notice to Nasdaq of our intention to cure the deficiency during the additional compliance period. Following a transfer to The Nasdaq Capital Market, under Nasdaq Listing Rules, the Company may be eligible for an additional 180 calendar day compliance period. The Company is actively monitoring its stock price and will consider any and all options available to regain compliance. The alternatives to trading on the Nasdaq Stock Market or another national securities exchange are generally considered to be less efficient and less broad-based than the national securities exchanges and the liquidity of the Company’s common stock will likely be reduced if it fails to regain compliance with the Minimum Bid Price Requirement.

The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has incurred recurring losses since inception, including a net loss of $6.1 million for the three months ended March 31, 2020. As of March 31, 2020, the Company had an accumulated deficit of $130.0 million. The Company expects to continue to generate operating losses in the foreseeable future. As of the issuance date of the interim consolidated financial statements, the Company expects that its cash and cash equivalents will be sufficient to fund its operating expenses and capital expenditure requirements into mid-2021. Based on our available cash resources, recurring losses and cash outflows from operations, since our inception, an expectation of continuing operating losses and cash outflows from operations for the foreseeable future, we have concluded that there is substantial doubt about our ability to continue as a going concern. The financial statements do not include any adjustments that might result from the outcome of this uncertainty.

The Company expects that it will continue to incur significant expenses in connection with its ongoing business activities. The Company will need to seek additional funding through equity offerings, debt financings, collaborations, licensing arrangements and other marketing and distribution arrangements, partnerships, joint ventures, combinations or divestitures of one or more of its businesses. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborative arrangements or divest its assets. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Arrangements with collaborators or others may require the Company to relinquish rights to certain of its technologies or product candidates. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate its research and development programs or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations.

The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”).

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Unaudited Interim Financial Information

The consolidated balance sheet at December 31, 2019 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of March 31, 2020 and for the three months ended March 31, 2020 and 2019 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (SEC) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of March 31, 2020 and results of operations for the three months ended March 31, 2020 and 2019 and cash flows for the three months ended March 31, 2020 and 2019 have been made. The Company’s results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020.

Principles of Consolidation

The accompanying consolidated financial statements include those of the Company and its wholly-owned subsidiary, Mono, Inc. All intercompany balances and transactions have been eliminated.

Risks and Uncertainties - Impact of the COVID-19 Coronavirus

The Company is subject to risks and uncertainties as a result of the COVID-19 pandemic. The virus continues to spread globally, has been declared a pandemic by the World Health Organization and has spread to over 100 countries, including the United States. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world.

The spread of COVID-19 has caused us to modify our business practices, including implementing a work-from-home policy for all employees who are able to perform their duties remotely and restricting all nonessential travel, and we expect to continue to take actions as may be required or recommended by government authorities or as we determine are in the best interests of our employees, the patients we serve and other business partners in light of COVID-19. Potential impacts to our business include temporary closures of our facilities or those of our vendors, disruptions or restrictions on our employees’ ability to travel, disruptions to or delays in ongoing laboratory experiments and operations and the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, and our ability to raise capital. As of March 31, 2020, there have been no material impacts to the Company. As the impacts of COVID-19 continue to unfold, the Company will continually assess the impacts, as the extent to which the COVID-19 pandemic may materially impact the Company’s financial condition, liquidity or results of operations in the future is uncertain.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions, and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, the accrual of research and development expenses and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. The extent to which the COVID-19 pandemic may directly or indirectly impact our business, financial condition, and results of operations is highly uncertain and subject to change. We considered the potential impact of the COVID-19 pandemic on our estimates and assumptions and there was not a material impact to our condensed consolidated financial statements as of and for the three months ended March 31, 2020; however, actual results could differ from those estimates and there may be changes to our estimates in future periods.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires certain financial assets measured at amortized cost be presented at the net amount expected to be collected. The Company adopted ASU 2016-13 on January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements.

In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606. The main provisions of ASU 2018-18 include: (i) clarifying that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and (ii) precluding the presentation of transactions with collaborative arrangement participants that are not directly related to sales to third parties together with revenue. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The guidance per ASU 2018-18 is to be adopted retrospectively to the date of initial application of Topic 606. The Company adopted ASU 2018-18 on January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, (“ASU 2018-13”). The new standard removes certain disclosures, modifies certain disclosures and adds additional disclosures related to fair value measurement. The new standard became effective on January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements.

Recently Issued Accounting Pronouncements Not Yet Adopted

In December 2019, the FASB issued ASU 2019-12 Simplifying the Accounting for Income Taxes, which eliminates the need for an organization to analyze whether the following apply in a given period: (1) exception to the incremental approach for intra-period tax allocation; (2) exceptions to accounting for basis differences when there are ownership changes in foreign investments; and (3) exceptions in interim period income tax accounting for year-to-date losses that exceed anticipated losses. ASU No. 2019-12 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. The Company does not expect that this standard will have a material effect on its consolidated financial statements.

Marketable Securities and Fair Value of Financial Assets and Liabilities

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Marketable Securities and Fair Value of Financial Assets and Liabilities

3. Fair Value of Financial Assets and Liabilities

The following tables present information about the Company’s assets that are measured at fair value on a recurring basis (in thousands):

	Fair Value Measurements at March 31, 2020 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	487	$	—	$	487
	$	—	$	487	$	—	$	487

	Fair Value Measurements at December 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	485	$	—	$	485
	$	—	$	485	$	—	$	485

We evaluate transfers between levels at the end of each reporting period. We have no financial assets or liabilities that were classified as Level 3 at any point during the three months ended March 31, 2020.

- 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

Accrued Expenses and Other Current Liabilities

3 Months Ended

Mar. 31, 2020

Payables And Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

4. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	March 31, 2020		December 31, 2019
Accrued employee compensation and benefits	$	1,185	$	2,500
Accrued external research and development expense		3,436		2,987
Accrued external manufacturing costs		590		750
Other		912		894
	$	6,123	$	7,131

Collaboration Agreement

3 Months Ended

Mar. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration Agreement

5. Collaboration Agreement

In June 2015, the Company entered into a Collaboration Agreement with Seattle Genetics (the “Collaboration Agreement”). Pursuant to the terms of the Collaboration Agreement, the Company and Seattle Genetics agreed to jointly develop two product candidates incorporating our ACTR platform and Seattle Genetics’ antibodies. Under the Collaboration Agreement, we conduct preclinical research and clinical development activities related to the two specified product candidates through Phase 1 clinical development, and Seattle Genetics provides the funding for those activities. Seattle Genetics will continue development activities of the two specified product candidates in collaboration with the Company unless it exercises one of its two options to opt-out from further development and commercialization activities for each of the two product candidates during specified periods subsequent to Phase 1 clinical development. In addition, the Company has an option to opt-out from further development and commercialization activities for each of the two product candidates, exercisable during a specified period subsequent to Phase 2 clinical development. If neither party exercises its options to opt-out from further development and commercialization activities for each product candidate, the parties will work together to co-develop and fund each product candidate after Phase 1 clinical development and Seattle Genetics will pay the Company specified collaboration and milestone payments upon the occurrence of specified events related to each product candidate of up to an aggregate of $400.0 million across the two active product candidates, consisting of $100.0 million of aggregate collaboration payments, $100.0 million of aggregate regulatory milestone payments and $200.0 million of aggregate commercial milestone payments. The individual collaboration payments are payable upon the occurrence of specified clinical development events and range up to $30.0 million per product candidate. The individual regulatory milestone payments are payable upon the first regulatory approval of each product in the United States and the first regulatory approval of each product in specified territories outside the United States and range up to $35.0 million per product. The individual commercial milestone payments are payable upon the achievement of specified aggregate annual net sales for each product and range up to $60.0 million per product. Through December 31, 2019, no milestones had been achieved or paid.

On January 16, 2020, the Company and Seattle Genetics entered into an agreement to terminate the Collaboration Agreement (the “Termination Agreement”) effective as of January 16, 2020 (the “Termination Effective Date”), pursuant to which the Parties will cease all research, development, manufacturing and other exploitations of any and all research candidates and development candidates under the Collaboration Agreement, including, without limitation, the development candidate ACTR-BCMA and a research candidate.

Pursuant to terms of the Termination Agreement, among other things, (i) Seattle Genetics paid the Company $5.75 million, (ii) Seattle Genetics surrendered, assigned and transferred to the Company all of its right, title and interest in the 831,847 shares of the Company’s common stock owned by Seattle Genetics, (iii) the Company will continue to pay all expenses for the wind-down of the ACTR-BCMA trial and (iv) Seattle Genetics paid all research and development costs incurred through the Termination Effective Date. In addition, the exclusivity provisions in the Collaboration Agreement terminate and each party will be free to research, develop and commercialize its individual intellectual property either by themselves or with third parties, subject to the intellectual property rights of the other party.

In considering all facts, including the suspension of the ATTCK-17-01 clinical trial as announced in November 2019 and the expected termination of the Collaboration Agreement in January 2020, as of December 31, 2019, the Company adjusted the estimated transaction price to be the $25.0 million upfront payment from 2015 and the total payments to be earned for preclinical research and clinical development activities through the Termination Date. During the three months ended March 31, 2020, the Company adjusted the transaction price to include the Termination Payment of $5.75 million as well as the aggregate fair value of $0.8 million as of January 16, 2020 of the 831,847 shares of common stock received. The aggregate fair value of common stock received has been included as a noncash adjustment to reconcile net loss to net cash used in operating activities within the consolidated statement of cash flows. The Company also adjusted the costs to complete the remaining performance obligations to represent our best estimate as of March 31, 2020.

Under the Collaboration Agreement and Termination Agreement, the Company recognized revenue of $7.0 million and $3.1 million for the three months ended March 31, 2020 and 2019, respectively. As of March 31, 2020 and December 31, 2019, deferred revenue of $0.8 million and $1.3 million, respectively, was recorded related to these agreements. As of March 31, 2020, the aggregate amount of the transaction price allocated to the remaining performance obligation for preclinical research and clinical development activities related to the two specified product candidates through Phase 1 is estimated to be approximately $0.8 million, which is expected to be recognized as revenue through fiscal 2020.

Loan and Security Agreement

3 Months Ended

Mar. 31, 2020

Debt Disclosure [Abstract]

Loan and Security Agreement

6. Loan and Security Agreement

The Company has a loan and security agreement (the “Loan Agreement”) with Pacific Western Bank (“PWB”), entered into in 2017, which provided for term loan borrowings of up to $15.0 million through January 19, 2019. Borrowings under the Loan Agreement bear interest at a variable annual rate equal to the greater of (i) the prime rate plus 0.25% or (ii) 3.75%, and were payable over an interest-only period until January 19, 2019, followed by a 24-month period of equal monthly payments of principal and interest. All amounts outstanding as of the maturity date of January 19, 2021 become immediately due and payable. In January 2019, the Company amended the Loan Agreement to extend the available date for borrowings from January 19, 2019 to June 30, 2019 and extend the interest only period from January 19, 2019 to June 30, 2020, with the possibility of further extension to March 31, 2021 if certain equity financing considerations are met. Additionally, the loan repayment period will be over a 24-month period following the end of the interest-only period. In June 2019, the Company further amended the Loan Agreement to extend the available date for borrowings from June 30, 2019 to June 30, 2020. On July 31, 2019, the Company amended the Loan Agreement to provide for changes to the primary depository requirements with PWB.

In connection with the Loan Agreement, the Company agreed to enter into warrant agreements with PWB pursuant to which warrants will be issued to purchase a number of shares of the Company’s capital stock equal to 1% of the amount of each term loan borrowing under the Loan Agreement, divided by the applicable exercise price.

No amounts have been borrowed as term loans under the Loan Agreement as of March 31, 2020. Potential borrowings under the Loan Agreement are collateralized by substantially all of the Company’s assets, except for its intellectual property. Under the Loan Agreement, the Company has agreed to affirmative and negative covenants to which it will remain subject until maturity. These covenants include limitations on the Company’s ability to incur additional indebtedness and engage in certain fundamental business transactions, such as mergers or acquisitions of other businesses. There are no financial covenants associated with the Loan Agreement. Events of default under the Loan Agreement include failure to make payments when due, insolvency events, failure to comply with covenants and material adverse effects with respect to the Company.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

7. Stock-Based Compensation

2018 Stock Option and Incentive Plan

The Company’s 2018 Stock Option and Incentive Plan, (the “2018 Plan”), which became effective on March 27, 2018 provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards, cash-based awards and dividend equivalent rights. The number of shares initially reserved for issuance under the 2018 Plan was 2,800,721. Additionally, the shares of common stock that remained available for issuance under the previously outstanding 2015 Stock Incentive Plan (the “2015 Plan”) became available under the 2018 Plan. The number of shares reserved for the 2018 Plan automatically increase on each January 1 by 4% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or a lesser number of shares determined by the Company’s board of directors. The shares of common stock underlying any awards that are forfeited, canceled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, repurchased or are otherwise terminated by the Company under the 2018 Plan or the 2015 Plan will be added back to the shares of common stock available for issuance under the 2018 Plan. The number of authorized shares reserved for issuance under the 2018 Plan was increased by 1,226,500 shares effective as of January 1, 2020. As of March 31, 2020, 3,612,870 shares remained available for future issuance under the 2018 Plan.

2018 Employee Stock Purchase Plan

The Company’s 2018 Employee Stock Purchase Plan (the “ESPP”) became effective on March 28, 2018 at which time a total of 314,000 shares of common stock were reserved for issuance. In addition, the number of shares of common stock that may be issued under the ESPP automatically increase on each January 1 through January 1, 2027, by the least of (i) 500,000 shares of common stock, (ii) 1% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or (iii) such lesser number of shares as determined by the ESPP administrator. The number of authorized shares reserved for issuance under the ESPP was increased by 306,631 shares effective as of January 1, 2020. The first six month offering period was initiated on July 1, 2019. As of March 31, 2020, 57,011 shares have been issued under the ESPP and 864,200 shares remain available for issuance.

Stock Option Issuances

During the three months ended March 31, 2020, the Company granted service-based options to participants for the purchase of 2,001,600 shares of common stock with a weighted average exercise price of $5.28 per share and a weighted average grant-date fair value of $0.54 per share.

During three months ended March 31, 2019, the Company granted options to certain employees for the purchase of 635,000 shares of common stock with a weighted average grant-date fair value of $2.46 per share that vest under a combination of performance-based and service-based vesting conditions if certain performance vesting criteria are achieved on or before March 31, 2020. As of March 31, 2020, the Company has not recorded stock-based compensation expense as the performance conditions were not met and the options were subsequently canceled.

Stock-Based Compensation

The Company recorded stock-based compensation expense in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):

	Three Months Ended March 31,
	2020		2019
Research and development expenses	$	237	$	599
General and administrative expenses		532		127
Total	$	769	$	726

As of March 31, 2020, total unrecognized compensation cost related to the unvested stock-based awards was $3.6 million, which is expected to be recognized over a weighted average period of 2.91 years.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

8. Commitments and Contingencies

License Agreement

Under its license agreement with National University of Singapore and St. Jude Children’s Research Hospital, Inc. (collectively the “Licensors”) entered into in 2014, the Company is obligated to pay license maintenance fees on each anniversary of the effective date of the agreement that escalate from less than $0.1 million for each of the first seven years to $0.1 million on the eighth anniversary and each year thereafter. The Company is also obligated to make aggregate milestone payments of up to 5.5 million Singapore dollars (equivalent to approximately $3.9 million as of March 31, 2020) upon the achievement of specified clinical and regulatory milestones and to pay tiered royalties ranging in the low single-digit percentages on annual net sales of licensed products sold by the Company or its sublicensees. The royalties are payable on a product-by-product and country-by-country basis and may be reduced in specified circumstances. Additionally, under certain circumstances, the Company is obligated to pay the Licensors a percentage of amounts received from sublicensees.

The license agreement will expire on a country-by-country basis until the last to expire of the patents and patent applications covering such licensed product or service. The Licensors may terminate the license agreement within 60 days after written notice in the event of a breach of contract. The Licensors may also terminate the agreement upon written notice in the event of the Company’s bankruptcy, liquidation, or insolvency. In addition, the Company has the right to terminate this agreement in its entirety at will upon 90 days’ advance written notice to the Licensors. However, if the Company has commenced the commercialization of licensed products, the Company can only terminate at will if it ceases all development and commercialization of licensed products. As of March 31, 2020, no milestones have been met.

Manufacturing Commitment

As of March 31, 2020, the Company had non-cancelable minimum purchase commitments under contract manufacturing agreements for payments totaling $0.3 million over the following 12 months.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of March 31, 2020 or December 31, 2019.

Legal Proceedings

The Company is not currently party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses as incurred the costs related to such legal proceedings.

Net Loss Per Share

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

Net Loss Per Share

9. Net Loss Per Share

Basic and diluted net loss per common share was calculated as follows (in thousands, except share and per share amounts):

	Three Months Ended March 31,
	2020			2019
Numerator:
Net loss	$	(6,094	)	$	(11,691	)
Denominator:
Weighted average common shares outstanding, basic and diluted		30,136,749			30,083,006
Net loss per common share, basic and diluted	$	(0.20	)	$	(0.39	)

The Company’s potential dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be anti-dilutive and would result in a reduction to net loss per share. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated above because including them would have had an anti-dilutive effect:

	March 31,
	2020		2019
Stock options to purchase common stock		4,105,808		4,267,697
Unvested restricted common stock units		353,485		—
		4,459,293		4,267,697

Retirement Plan

3 Months Ended

Mar. 31, 2020

Compensation And Retirement Disclosure [Abstract]

Retirement Plan

10. Retirement Plan

The Company has a defined-contribution plan under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. As currently established, the Company is not required to make and to date has not made any contributions to the 401(k) Plan. The Company did not make any matching contributions during the three months ended March 31, 2020 and 2019.

Restructuring

3 Months Ended

Mar. 31, 2020

Restructuring And Related Activities [Abstract]

Restructuring

11. Restructuring

On March 2, 2020, the Company announced the board of directors approved plans to reduce workforce and prioritize resources towards advancing the Company’s preclinical program, BOXR1030, for the treatment of solid tumor cancers. As a result, the Company reduced its headcount by approximately 60% in the quarter ended March 31, 2020.

The Company incurred restructuring charges consisting of one-time severance payments and other employee related costs of $1.7 million in the quarter ended March 31, 2020. Cash payments for employee related restructuring charges of $1.1 million were paid as of March 31, 2020. The remaining $0.6 million of payments will be paid in the second quarter of 2020. The Company recorded these restructuring charges based on each employee’s role to the respective research and development and general and administrative operating expense categories of $1.3 million and $0.4 million, respectively, on its consolidated statements of operations and comprehensive loss.

A summary of the charges related to the restructuring activities as of March 31, 2020 is as follows (in thousands):

	Balance at							Balance at
	December 31, 2019		Charges		Less: Payments			March 31, 2020
Severance, benefits and relates costs	$	—	$	1,700	$	(1,138	)	$	562
Total	$	—	$	1,700	$	(1,138	)	$	562

These amounts are included in accounts payable, accrued expenses and other current liabilities in the March 31, 2020 consolidated balance sheet.

Subsequent Events

3 Months Ended

Mar. 31, 2020

Subsequent Events [Abstract]

Subsequent Events

12. Subsequent Events

On April 8, 2020, the Company launched a tender offer by the Company to certain employee optionholders, subject to specified conditions, to exchange some or all of their outstanding options to purchase shares of common stock, par value $0.001 per share, for equivalent number of new options to purchase shares of the Company’s common stock. As disclosed in the Company’s Definitive Proxy Statement filed with the Securities and Exchange Commission on February 18, 2020, the Company’s chief executive officer, and members of the Company’s board of directors are not eligible to participate in this tender offer.

Pursuant to the Exchange Offer, all eligible employees elected to exchange outstanding options, and the Company accepted for cancellation options to purchase an aggregate of 2,169,674 shares of the Company’s common stock. On May 7, 2020, immediately following the expiration of the Exchange Offer, the company granted new options to purchase 2,169,674 shares of common stock, pursuant to the terms of the Exchange Offer and the Company’s 2018 Stock Option and Incentive Plan. In relation to the Exchange Option, in the quarter ending June 30, 2020, the Company will recognize $0.1 million of compensation cost immediately related to the incremental fair value of vested stock-based awards. The incremental fair value of unvested stock-based awards that will be recognized prospectively over the remaining requisite service period is $0.1 million.

In April 2020, our board of directors unanimously approved an amendment to our certificate of incorporation, which would allow the board to effect a reverse stock split, or Reverse Stock Split, of all issued and outstanding shares of our common stock, at a ratio ranging from 1-for-5 to 1-for-10, inclusive, subject to shareholder approval. On April 29, 2020, the Company filed a Definitive Proxy Statement which includes the proposal that our stockholders approve the amendment to our certificate of incorporation to effect the Reverse Stock Split. The stockholders will vote on the proposal at the annual meeting on June 9, 2020. All disclosures of common shares and per common share data in the accompanying interim financial statements and related notes have not been adjusted to reflect the Reverse Stock Split.

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2020
Accounting Policies [Abstract]
Unaudited Interim Financial Information	Unaudited Interim Financial Information The consolidated balance sheet at December 31, 2019 was derived from audited financial statements but does not include all disclosures required by GAAP. The accompanying unaudited condensed consolidated financial statements as of March 31, 2020 and for the three months ended March 31, 2020 and 2019 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (SEC) for interim financial statements. Certain information and footnote disclosures normally included in the financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of March 31, 2020 and results of operations for the three months ended March 31, 2020 and 2019 and cash flows for the three months ended March 31, 2020 and 2019 have been made. The Company’s results of operations for the three months ended March 31, 2020 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2020.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include those of the Company and its wholly-owned subsidiary, Mono, Inc. All intercompany balances and transactions have been eliminated.
Risks and Uncertainties - Impact of the COVID-19 Coronavirus	Risks and Uncertainties - Impact of the COVID-19 Coronavirus The Company is subject to risks and uncertainties as a result of the COVID-19 pandemic. The virus continues to spread globally, has been declared a pandemic by the World Health Organization and has spread to over 100 countries, including the United States. The impact of this pandemic has been and will likely continue to be extensive in many aspects of society, which has resulted in and will likely continue to result in significant disruptions to the global economy, as well as businesses and capital markets around the world. The spread of COVID-19 has caused us to modify our business practices, including implementing a work-from-home policy for all employees who are able to perform their duties remotely and restricting all nonessential travel, and we expect to continue to take actions as may be required or recommended by government authorities or as we determine are in the best interests of our employees, the patients we serve and other business partners in light of COVID-19. Potential impacts to our business include temporary closures of our facilities or those of our vendors, disruptions or restrictions on our employees’ ability to travel, disruptions to or delays in ongoing laboratory experiments and operations and the potential diversion of healthcare resources away from the conduct of clinical trials to focus on pandemic concerns, and our ability to raise capital. As of March 31, 2020, there have been no material impacts to the Company. As the impacts of COVID-19 continue to unfold, the Company will continually assess the impacts, as the extent to which the COVID-19 pandemic may materially impact the Company’s financial condition, liquidity or results of operations in the future is uncertain.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates, assumptions, and judgments that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, revenue recognition, the accrual of research and development expenses and the valuation of stock-based awards. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. The extent to which the COVID-19 pandemic may directly or indirectly impact our business, financial condition, and results of operations is highly uncertain and subject to change. We considered the potential impact of the COVID-19 pandemic on our estimates and assumptions and there was not a material impact to our condensed consolidated financial statements as of and for the three months ended March 31, 2020; however, actual results could differ from those estimates and there may be changes to our estimates in future periods.
Recently Adopted and Issued Accounting Pronouncements Not Yet Adopted	Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires certain financial assets measured at amortized cost be presented at the net amount expected to be collected. The Company adopted ASU 2016-13 on January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606. The main provisions of ASU 2018-18 include: (i) clarifying that certain transactions between collaborative arrangement participants should be accounted for as revenue when the collaborative arrangement participant is a customer in the context of a unit of account and (ii) precluding the presentation of transactions with collaborative arrangement participants that are not directly related to sales to third parties together with revenue. This guidance will be effective for annual reporting periods beginning after December 15, 2019, including interim periods within those annual reporting periods, and early adoption is permitted. The guidance per ASU 2018-18 is to be adopted retrospectively to the date of initial application of Topic 606. The Company adopted ASU 2018-18 on January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, (“ASU 2018-13”). The new standard removes certain disclosures, modifies certain disclosures and adds additional disclosures related to fair value measurement. The new standard became effective on January 1, 2020. The adoption of this guidance did not have a material impact on the Company’s condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Adopted In December 2019, the FASB issued ASU 2019-12 Simplifying the Accounting for Income Taxes, which eliminates the need for an organization to analyze whether the following apply in a given period: (1) exception to the incremental approach for intra-period tax allocation; (2) exceptions to accounting for basis differences when there are ownership changes in foreign investments; and (3) exceptions in interim period income tax accounting for year-to-date losses that exceed anticipated losses. ASU No. 2019-12 is effective for fiscal years beginning after December 15, 2020, and interim periods within those fiscal years. The Company does not expect that this standard will have a material effect on its consolidated financial statements.

Marketable Securities and Fair Value of Financial Assets and Liabilities (Tables)

3 Months Ended

Mar. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s assets that are measured at fair value on a recurring basis (in thousands):

	Fair Value Measurements at March 31, 2020 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	487	$	—	$	487
	$	—	$	487	$	—	$	487

	Fair Value Measurements at December 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	485	$	—	$	485
	$	—	$	485	$	—	$	485

Accrued Expenses and Other Current Liabilities (Tables)

3 Months Ended

Mar. 31, 2020

Payables And Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):

	March 31, 2020		December 31, 2019
Accrued employee compensation and benefits	$	1,185	$	2,500
Accrued external research and development expense		3,436		2,987
Accrued external manufacturing costs		590		750
Other		912		894
	$	6,123	$	7,131

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock Based Compensation Expense

The Company recorded stock-based compensation expense in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):

	Three Months Ended March 31,
	2020		2019
Research and development expenses	$	237	$	599
General and administrative expenses		532		127
Total	$	769	$	726

Net Loss per Share (Tables)

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

Schedule of Earnings Per Share Basic and Diluted

Basic and diluted net loss per common share was calculated as follows (in thousands, except share and per share amounts):

	Three Months Ended March 31,
	2020			2019
Numerator:
Net loss	$	(6,094	)	$	(11,691	)
Denominator:
Weighted average common shares outstanding, basic and diluted		30,136,749			30,083,006
Net loss per common share, basic and diluted	$	(0.20	)	$	(0.39	)

Summary of Potential Dilutive Securities

	March 31,
	2020		2019
Stock options to purchase common stock		4,105,808		4,267,697
Unvested restricted common stock units		353,485		—
		4,459,293		4,267,697

Restructuring (Tables)

3 Months Ended

Mar. 31, 2020

Restructuring And Related Activities [Abstract]

Summary of Charges Related to Restructuring Activities

A summary of the charges related to the restructuring activities as of March 31, 2020 is as follows (in thousands):

	Balance at							Balance at
	December 31, 2019		Charges		Less: Payments			March 31, 2020
Severance, benefits and relates costs	$	—	$	1,700	$	(1,138	)	$	562
Total	$	—	$	1,700	$	(1,138	)	$	562

Nature of the Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		12 Months Ended
	Mar. 02, 2020 Employee	Apr. 01, 2019 USD ($)	Mar. 31, 2020 USD ($) shares	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Mar. 19, 2020 shares
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Employee workforce, termination percentage	60.00%		60.00%
Number of employees expected to be terminated \| Employee	43
Common stock, Shares authorized			150,000,000		150,000,000
Common stock, Shares issued			30,821,892		30,663,054
Deficiency letter from listing qualifications department notifying period					30 days
Minimum bid price of common stock \| $ / shares					$ 1.00
Initial period to regain compliance with minimum bid price rule					180 days
Additional period to regain compliance with minimum bid price rule					180 days
Net loss \| $			$ (6,094)	$ (11,691)
Accumulated deficit \| $			$ (129,986)		$ (123,892)
Cowen [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Shares of common stock issued and sold			0
Lincoln Park Capital Fund [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Common stock, Shares authorized						25,000,000
Common stock, Shares issued						726,382
Maximum [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Proceeds from issuance of equity and debt financing \| $		$ 150,000
Maximum [Member] \| Cowen [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Stock offering cost \| $		$ 50,000

Marketable Securities and Fair Value of Financial Assets and Liabilities - Schedule of Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value on Recurring Basis	$ 487	$ 485
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value on Recurring Basis	487	485
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents Measured at Fair Value on Recurring Basis	487	485
Money Market Funds [Member] \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash Equivalents Measured at Fair Value on Recurring Basis	$ 487	$ 485

Marketable Securities and Fair Value of Financial Assets and Liabilities - Additional Information (Detail)	Mar. 31, 2020 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Fair value asset, transfers involving Level 3, amount	$ 0
Fair value liability, transfers involving Level 3, amount	$ 0

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued employee compensation and benefits	$ 1,185	$ 2,500
Accrued external research and development expense	3,436	2,987
Accrued external manufacturing costs	590	750
Other	912	894
Total	$ 6,123	$ 7,131

Collaboration Agreement - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		55 Months Ended
	Jan. 16, 2020	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue related to research and clinical development activities		$ 7,031	$ 3,053
Seattle Genetics [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement consideration received upon termination agreement	$ 5,750
Collaborative arrangement common stock surrender	831,847
Collaborative arrangement fair value of common stock surrender	$ 800
Revenue related to research and clinical development activities		7,000	$ 3,100
Deferred revenue		800		$ 1,300
Remaining performance obligation related to two product candidates		800
Preclinical Research And Clinical Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement upfront payment recognized				$ 25,000
Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		100,000
Regulatory Milestone Payments [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		100,000
Commercial Milestone Payments [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		200,000
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		400,000
Maximum [Member] \| Collaborative Arrangement [Member] \| Clinical Development Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		30,000
Maximum [Member] \| Regulatory Milestone Payments [Member] \| First Regulatory Approval [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		35,000
Maximum [Member] \| Commercial Milestone Payments [Member] \| Annual Net Sales Achievement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future collaboration and milestone payments		$ 60,000

Loan and Security Agreement - Additional Information (Detail) - Loan and Security Agreement [Member] - Pacific Western Bank [Member]	3 Months Ended
	Mar. 31, 2020 USD ($)
Debt Instrument [Line Items]
Warrant to be issued to purchase number of shares capital stock equal to the amount of each term loan borrowing percentage	1.00%
Term Loan [Member]
Debt Instrument [Line Items]
Maximum term loan borrowings	$ 15,000,000
Interest rate during period	3.75%
Term loan payment terms	The Company has a loan and security agreement (the “Loan Agreement”) with Pacific Western Bank (“PWB”), entered into in 2017, which provided for term loan borrowings of up to $15.0 million through January 19, 2019. Borrowings under the Loan Agreement bear interest at a variable annual rate equal to the greater of (i) the prime rate plus 0.25% or (ii) 3.75%, and were payable over an interest-only period until January 19, 2019, followed by a 24-month period of equal monthly payments of principal and interest. All amounts outstanding as of the maturity date of January 19, 2021 become immediately due and payable. In January 2019, the Company amended the Loan Agreement to extend the available date for borrowings from January 19, 2019 to June 30, 2019 and extend the interest only period from January 19, 2019 to June 30, 2020, with the possibility of further extension to March 31, 2021 if certain equity financing considerations are met. Additionally, the loan repayment period will be over a 24-month period following the end of the interest-only period. In June 2019, the Company further amended the Loan Agreement to extend the available date for borrowings from June 30, 2019 to June 30, 2020. On July 31, 2019, the Company amended the Loan Agreement to provide for changes to the primary depository requirements with PWB.
Outstanding amount maturity date	Jan. 19, 2021
Term of loan	24 months
Term loan frequency of periodic payment	monthly
Term loans borrowed	$ 0
Term Loan [Member] \| Prime Rate [Member]
Debt Instrument [Line Items]
Annual variable interest rate	0.25%

Stock-Based Compensation - Additional Information (Detail) - USD ($)				3 Months Ended
	Jan. 01, 2020	Mar. 28, 2018	Mar. 27, 2018	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock share issued				30,821,892		30,663,054
Share based compensation expense				$ 769,000	$ 726,000
Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants					635,000
Weighted average grant date fair value					$ 2.46
Service Based Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants				2,001,600
Weighted average exercise price				$ 5.28
Weighted average grant date fair value				$ 0.54
Performance Based Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense				$ 0
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost				$ 3,600,000
Unrecognized compensation expenses, recognition period				2 years 10 months 28 days
2018 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of increases in authorized shares			2,800,721
Percentage applied to the outstanding shares as annual increase in the number of shares authorized for issuance			4.00%
Increased in authorized shares reserved for issuance	1,226,500
Shares available for future issuance				3,612,870
2018 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increased in authorized shares reserved for issuance	306,631
Shares available for future issuance				864,200
Shares reserved for future issuance		314,000
Common stock share issued				57,011
2018 Employee Stock Purchase Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of increases in authorized shares		500,000
Percentage of shares of common stock available for issuance		1.00%

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation expense	$ 769	$ 726
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation expense	237	599
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation expense	$ 532	$ 127

Commitments and Contingencies - Additional Information (Detail) - 3 months ended Mar. 31, 2020	USD ($)	SGD ($)
Commitments And Contingencies Disclosure [Line Items]
Non-cancelable minimum purchase commitments	$ 300,000
License Agreement [Member]
Commitments And Contingencies Disclosure [Line Items]
License agreement expiration terms	The license agreement will expire on a country-by-country basis until the last to expire of the patents and patent applications covering such licensed product or service. The Licensors may terminate the license agreement within 60 days after written notice in the event of a breach of contract. The Licensors may also terminate the agreement upon written notice in the event of the Company’s bankruptcy, liquidation, or insolvency. In addition, the Company has the right to terminate this agreement in its entirety at will upon 90 days’ advance written notice to the Licensors. However, if the Company has commenced the commercialization of licensed products, the Company can only terminate at will if it ceases all development and commercialization of licensed products. As of March 31, 2020, no milestones have been met.
Eighth Year Anniversary and Thereafter [Member] \| License Agreement [Member]
Commitments And Contingencies Disclosure [Line Items]
License maintenance fees	$ 100,000
Maximum [Member] \| License Agreement [Member]
Commitments And Contingencies Disclosure [Line Items]
Contingent contractual obligation	3,900,000	$ 5,500,000
Maximum [Member] \| First Seven Year Anniversary [Member] \| License Agreement [Member]
Commitments And Contingencies Disclosure [Line Items]
License maintenance fees	$ 100,000

Net Loss Per Share - Schedule of Earnings Per Share Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net loss	$ (6,094)	$ (11,691)
Weighted average common shares outstanding, basic and diluted	30,136,749	30,083,006
Net loss per common share, basic and diluted	$ (0.20)	$ (0.39)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss Per Share - Summary of Potential Dilutive Securities (Detail) - shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	4,459,293	4,267,697
Unvested Restricted Common Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	353,485
Stock Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	4,105,808	4,267,697

Retirement Plan - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan, matching amount	$ 0	$ 0

Restructuring - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended
	Mar. 02, 2020	Jun. 30, 2020	Mar. 31, 2020
Restructuring Cost And Reserve [Line Items]
Employee workforce, termination percentage	60.00%		60.00%
Severance and employee termination related costs			$ 1,700
Cash payments for employee related restructuring charges			1,138
Research and Development Expense [Member]
Restructuring Cost And Reserve [Line Items]
Severance and employee termination related costs			1,300
General and Administrative Expense [Member]
Restructuring Cost And Reserve [Line Items]
Severance and employee termination related costs			$ 400
Forecast
Restructuring Cost And Reserve [Line Items]
Cash payments for employee related restructuring charges		$ 600

Restructuring - Summary of Charges Related to Restructuring Activities (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring, beginning balance
Charges	$ 1,700
Less: Payments	(1,138)
Restructuring, ending balance	562
Severance Benefits and Related Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring, beginning balance
Charges	1,700
Less: Payments	(1,138)
Restructuring, ending balance	$ 562

Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended
	May 07, 2020 shares	Apr. 30, 2020	Jun. 30, 2020 USD ($)	May 06, 2020 shares	Apr. 08, 2020 $ / shares	Mar. 31, 2020 $ / shares	Dec. 31, 2019 $ / shares
Subsequent Event [Line Items]
Common stock, Par value \| $ / shares						$ 0.001	$ 0.001
Subsequent Event [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Reverse stock split description		1-for-5 to 1-for-10
Subsequent Event [Member] \| Minimum [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Reverse stock split ratio		0.2
Subsequent Event [Member] \| Maximum [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Reverse stock split ratio		0.1
Stock Option [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, Par value \| $ / shares					$ 0.001
Authorized cancellation options and option re-grants \| shares				2,169,674
Stock Option [Member] \| Subsequent Event [Member] \| Exchange Offer and 2018 Stock Option and Incentive Plan [Member]
Subsequent Event [Line Items]
Option grants \| shares	2,169,674
Vested Stock-based Awards [Member] \| Forecast
Subsequent Event [Line Items]
Compensation cost related to incremental fair value of stock based awards \| $			$ 0.1
Unvested Stock-based Awards [Member] \| Forecast
Subsequent Event [Line Items]
Compensation cost related to incremental fair value of stock based awards \| $			$ 0.1