Chimerix (CMRX) 10-Q 1 May 24 2024 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2024	Apr. 26, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-35867
Entity Registrant Name	CHIMERIX, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0903395
Entity Address, Address Line One	2505 Meridian Parkway
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	Durham
Entity Address, State or Province	NC
Entity Address, Postal Zip Code	27713
City Area Code	919
Local Phone Number	806-1074
Title of each class	Common Stock, par value $0.001 per share
Trading Symbol(s)	CMRX
Name of each exchange on which registered	NASDAQ
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		89,629,902
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001117480
Current Fiscal Year End Date	--12-31

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 19,026	$ 27,661
Short-term investments, available-for-sale	140,002	155,174
Accounts receivable	1	4
Prepaid expenses and other current assets	4,003	6,271
Total current assets	163,032	189,110
Long-term investments	29,133	21,657
Property and equipment, net of accumulated depreciation	263	224
Operating lease right-of-use assets	1,354	1,482
Other long-term assets	260	301
Total assets	194,042	212,774
Current liabilities:
Accounts payable	3,823	2,851
Accrued liabilities	15,112	15,592
Total current liabilities	18,935	18,443
Line of credit commitment fee	0	125
Lease-related obligations	1,005	1,177
Total liabilities	19,940	19,745
Stockholders’ equity:
Preferred stock, $0.001 par value, 10,000,000 shares authorized at March 31, 2024 and December 31, 2023; no shares issued and outstanding as of March 31, 2024 and December 31, 2023	0	0
Common stock, $0.001 par value, 200,000,000 shares authorized at March 31, 2024 and December 31, 2023; 89,629,902 and 88,929,300 shares issued and outstanding as of March 31, 2024 and December 31, 2023, respectively	90	89
Additional paid-in capital	991,583	988,457
Accumulated other comprehensive (gain) loss, net	(178)	7
Accumulated deficit	(817,393)	(795,524)
Total stockholders’ equity	174,102	193,029
Total liabilities and stockholders’ equity	$ 194,042	$ 212,774

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	89,629,902	88,929,300
Common stock, shares outstanding (in shares)	89,629,902	88,929,300

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Total revenues	$ 0	$ 283
Operating expenses:
Research and development	18,844	18,822
General and administrative	5,546	5,679
Total operating expenses	24,390	24,501
Loss from operations	(24,390)	(24,218)
Other income:
Interest income and other, net	2,521	2,846
Net loss	(21,869)	(21,372)
Other comprehensive (loss) income:
Unrealized (loss) gain on debt investments, net	(185)	106
Comprehensive loss	$ (22,054)	$ (21,266)
Per share information:
Net loss, basic (in dollars per share)	$ (0.25)	$ (0.24)
Net loss, diluted (in dollars per share)	$ (0.25)	$ (0.24)
Weighted-average shares outstanding, basic (in shares)	89,259,106	88,294,624
Weighted-average shares outstanding, diluted (in shares)	89,259,106	88,294,624
Contract and grant revenue
Total revenues	$ 0	$ 234
Licensing revenue
Total revenues	$ 0	$ 49

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2022		88,054,127
Beginning balance at Dec. 31, 2022	$ 256,857	$ 88	$ 970,535	$ (337)	$ (713,429)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	4,363		4,363
Employee stock purchase plan purchases (in shares)		308,000
Employee stock purchase plan purchases	357	$ 1	356
RSU stock issuance (in shares)		221,440
Comprehensive loss:
Unrealized (loss) gain on debt investments, net	106			106
Net loss	(21,372)				(21,372)
Comprehensive loss	(21,266)
Ending balance (in shares) at Mar. 31, 2023		88,583,567
Ending balance at Mar. 31, 2023	$ 240,311	$ 89	975,254	(231)	(734,801)
Beginning balance (in shares) at Dec. 31, 2023	88,929,300	88,929,300
Beginning balance at Dec. 31, 2023	$ 193,029	$ 89	988,457	7	(795,524)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	2,749		2,749
Employee stock purchase plan purchases (in shares)		419,546
Employee stock purchase plan purchases	378	$ 1	377
RSU stock issuance (in shares)		281,056
Comprehensive loss:
Unrealized (loss) gain on debt investments, net	(185)			(185)
Net loss	(21,869)				(21,869)
Comprehensive loss	$ (22,054)
Ending balance (in shares) at Mar. 31, 2024	89,629,902	89,629,902
Ending balance at Mar. 31, 2024	$ 174,102	$ 90	$ 991,583	$ (178)	$ (817,393)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities:
Net loss	$ (21,869)	$ (21,372)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation of property and equipment	22	22
Amortization of debt issuance costs	72	66
Amortization of discount/premium on investments	(1,191)	(2,096)
Share-based compensation	2,749	4,363
Lease-related amortization	(25)	(20)
Changes in operating assets and liabilities:
Accounts receivable	3	371
Prepaid expenses and other assets	2,280	441
Accounts payable and accrued liabilities	441	(4,000)
Net cash used in operating activities	(17,518)	(22,225)
Cash flows from investing activities:
Purchases of property and equipment	(27)	(62)
Purchases of short-term investments	(11,862)	0
Purchases of long-term investments	(29,236)	(6,803)
Proceeds from maturities of short-term investments	49,800	19,000
Net cash provided by investing activities	8,675	12,135
Cash flows from financing activities:
Proceeds from employee stock purchase plan	378	356
Payments of debt issuance costs	(170)	(157)
Net cash provided by financing activities	208	199
Net decrease in cash and cash equivalents	(8,635)	(9,891)
Cash and cash equivalents:
Beginning of period	27,661	25,842
End of period	$ 19,026	$ 15,951

The Business and Summary of Sig

The Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
The Business and Summary of Significant Accounting Policies	The Business and Summary of Significant Accounting Policies Description of Business Chimerix is a biopharmaceutical company whose mission it is to develop medicines that meaningfully improve and extend the lives of patients facing deadly diseases. The Company is focused on developing imipridones as a potential new class of selective cancer therapies. The most advanced imipridone is dordaviprone (ONC201) which is in clinical-stage development for H3 K27M-mutant diffuse glioma as its lead indication. In addition, a second-generation imipridone (ONC206) is currently in dose escalating clinical trials for adult and pediatric patients with primary central nervous system tumors. Basis of Presentation The accompanying unaudited consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. The accompanying unaudited consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP) for interim financial information, the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements and should be read in conjunction with the Company’s audited financial statements and notes thereto included in its Annual Report on Form 10-K for the year ended December 31, 2023. In the opinion of the Company’s management, all adjustments, consisting of normal recurring adjustments, necessary for a fair presentation of its financial position, operating results and cash flows for the periods presented have been included. Operating results for the three months ended March 31, 2024 are not necessarily indicative of the results that may be expected for the full year, for any other interim period or for any future year. Fair Value of Financial Instruments The carrying amounts of certain financial instruments, including accounts receivable, accounts payable and accrued expenses approximate their fair values due to the short-term nature of such instruments. For assets and liabilities recorded at fair value, it is the Company’s policy to maximize the use of observable inputs and minimize the use of unobservable inputs when developing fair value measurements, in accordance with the fair value hierarchy. Fair value measurements for assets and liabilities where there exists limited or no observable market data are based primarily upon estimates and are often calculated based on the economic and competitive environment, the characteristics of the asset or liability and other factors. Therefore, fair value measurements cannot be determined with precision and may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there may be inherent weaknesses in any calculation technique and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the calculated current or future fair values. The Company utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The Company groups assets and liabilities at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. The determination of where an asset or liability falls in the hierarchy requires significant judgment. These levels are: • Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. • Level 2 — Valuations based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and models for which all significant inputs are observable, either directly or indirectly. • Level 3 — Valuations based on inputs that are unobservable and significant to the overall fair value measurement. There was no material re-measurement to fair value of financial assets and liabilities that are not measured at fair value on a recurring basis. For additional information regarding the Company’s investments, please refer to Note 2, “Investments.” Below are tables that present information about certain assets measured at fair value on a recurring basis (in thousands): Fair Value Measurements March 31, 2024 Total Quoted Prices in Significant Other Significant Cash equivalents Money market funds $ 10,625 $ 10,625 $ — $ — Total cash equivalents 10,625 10,625 — — Short-term investments U.S. treasury securities 88,588 46,325 42,263 — Commercial paper 36,087 — 36,087 — Corporate bonds 15,327 — 15,327 — Total short-term investments 140,002 46,325 93,677 — Long-term investments U.S. treasury securities 29,133 5,959 23,174 — Total long-term investments 29,133 5,959 23,174 — Total assets $ 179,760 $ 62,909 $ 116,851 $ — Fair Value Measurements December 31, 2023 Total Quoted Prices in Significant Other Significant Cash equivalents Money market funds $ 24,102 $ 24,102 $ — $ — Total cash equivalents 24,102 24,102 — — Short-term investments U.S. treasury securities 99,779 40,336 59,443 — Commercial paper 44,319 — 44,319 — Corporate bonds 11,076 — 11,076 — Total short-term investments 155,174 40,336 114,838 — Long-term investments U.S. treasury securities 21,657 3,975 17,682 — Total long-term investments 21,657 3,975 17,682 — Total assets $ 200,933 $ 68,413 $ 132,520 $ — Employee Retention Credit Under the provisions of the Coronavirus Aid, Relief, and Economic Security Act (the CARES Act), the Company was eligible for a refundable employee retention credit subject to certain criteria. The Company recognized a $2.0 million employee retention credit during the three months ended September 30, 2022 related to labor costs recognized during 2020 and 2021, which is recorded in prepaid expenses and other current assets. For the three months ended September 30, 2022, $1.5 million was recorded as a reduction to research and development expenses and $0.5 million was recorded as a reduction to general and administrative expenses. The Company has filed for refunds of the employee retention credits and as of the date of this Quarterly Report on Form 10-Q, it has received $1.8 million of refunds and cannot reasonably estimate when it will receive any or all of the remaining refunds. Deferred Loan Costs On January 31, 2022 (the Effective Date), the Company entered into a Loan and Security Agreement (the Loan Agreement), by and between the Company, as borrower, and Silicon Valley Bank, now a division of First-Citizens Bank & Trust Company, as the lender (the Lender). The Loan Agreement provides for a four-year secured revolving loan facility (the Credit Facility) in an aggregate principal amount of up to $50.0 million. Proceeds from the Credit Facility may be used for working capital and general corporate purposes. The Company has no obligation to draw down any amount under the Credit Facility, and has not drawn down any amount as of March 31, 2024. On November 21, 2023, the Company entered into the First Amendment to the Loan Agreement, which among other things, extended the term to September 30, 2026 and increased the unused line fee to 0.35% per annum on the unused portion of the Credit Facility, payable quarterly in arrears. Borrowings under the Credit Facility accrue interest at a floating per annum rate of the greater of (i) 1.50% above the Prime Rate (as defined below) and (ii) 4.75%. Prime Rate is defined as the rate of interest per annum published in The Wall Street Journal or any successor publication thereto as the “Prime Rate”. If such rate of interest from The Wall Street Journal becomes unavailable, the “Prime Rate” shall mean the rate of interest per annum announced by the Lender as its prime rate in effect. In each case, in the event such prime rate is less than zero, such rate shall be deemed to be zero for purposes of the Loan Agreement. The Company must also pay an unused line fee equal to 0.35% per annum on the unused portion of the Credit Facility, payable quarterly in arrears. Upon the termination of the Loan Agreement for any reason prior to the Maturity Date, the Company will be required to pay to the Lender an early termination fee of $0.5 million. The Loan Agreement also requires the Company to pay the Lender a non-refundable commitment fee of $0.5 million, payable in four equal installments beginning on the Effective Date and each anniversary of the Effective Date thereafter until January 31, 2025. As of March 31, 2024, the Company has recorded current deferred loan costs of $0.1 million in prepaid expenses and other current assets and non-current deferred loan costs of $0.2 million in other long-term assets on the Consolidated Balance Sheets. As of March 31, 2024, the Company has recorded a current loan fee liability of $0.2 million in accrued liabilities. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, 2024 December 31, 2023 Accrued research and development expenses $ 9,445 $ 7,623 Accrued compensation 2,810 5,123 Other accrued liabilities 2,857 2,846 Total accrued liabilities $ 15,112 $ 15,592 Revenue Recognition Policy The Company’s revenues generally consist of (i) contract and grant revenue—revenue generated under federal and private foundation grants and contracts, (ii) licensing revenue—revenue related to non-refundable upfront fees, royalties and milestone payments earned under license agreements and (iii) royalty revenue—revenue related to sales of TEMBEXA made by Emergent after the Asset Sale. Revenue is recognized in accordance with the criteria outlined in Accounting Standards Codification (ASC) 606 issued by the Financial Accounting Standards Board (FASB). Following this accounting pronouncement, a five-step approach is applied for recognizing revenue, including (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when, or as, the entity satisfies a performance obligation. Emergent BioSolutions, Inc. On September 26, 2022, the Company completed the sale to Emergent of the Company’s exclusive worldwide rights to brincidofovir, including TEMBEXA® and specified related assets (the Asset Sale). Emergent paid the Company an upfront cash payment of approximately $238 million upon the closing of the Asset Sale. In addition, pursuant to the Asset Purchase Agreement, the Company is eligible to receive from Emergent: (i) up to an aggregate of approximately $124 million in milestone payments payable upon the exercise of the options under the BARDA Agreement (as defined below) for the delivery of up to 1.7 million treatment courses of tablet and suspension formulations of TEMBEXA to the U.S. government; (ii) royalty payments equal to 15% of all gross profits associated with the sales of TEMBEXA made outside of the United States during the exclusivity period of TEMBEXA on a market-to-market basis; (iii) royalty payments equal to 20% of future gross profits of TEMBEXA made in the United States associated with volumes above 1.7 million treatment courses of therapy during the exclusivity period of TEMBEXA; and (iv) up to an additional $12.5 million upon the achievement of certain other developmental milestones. The BARDA Agreement was novated to Emergent in December 2022. The Company recognized no contract revenue for support provided to Emergent for the three months ended March 31, 2024. The Company recognized $0.2 million of contract revenue for support provided to Emergent for the three months ended March 31, 2023. Grant Revenue Grant revenue under cost-plus-fixed-fee grants from the federal government and private foundations is recognized as allowable costs are incurred and fees are earned. At March 31, 2024, the Company has a deferred revenue balance of $0.1 million related to these grants. For the three months ended March 31, 2024, the Company recognized no grant revenue. For the three months ended March 31, 2023, the Company recognized $30,000 grant revenue related to these grants. Ohara Agreement In 2019, Oncoceutics, Inc., a Delaware corporation (Oncoceutics) which was subsequently acquired by the Company in January 2021, entered into a license, development and commercialization agreement with Ohara Pharmaceutical Co., Ltd. for dordaviprone in Japan. The Company is entitled to receive up to $2.5 million in nonrefundable regulatory milestone payments. The Company is entitled to double-digit tiered royalties based on the aggregate annual net sales of all products, as defined in the agreement, in Japan. For the three months ended March 31, 2024, the Company recognized no license revenue related to this agreement. For the three months ended March 31, 2023, the Company recognized approximately $0.1 million of license revenue related to this agreement. Research and Development Prepaids and Accruals As part of the process of preparing financial statements, the Company is required to estimate its expenses resulting from its obligation under contracts with vendors and consultants and clinical site agreements in connection with its research and development efforts. The financial terms of these contracts are subject to negotiations which vary contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate research and development expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of its research and development efforts. The Company determines prepaid and accrual estimates through discussion with applicable personnel and outside service providers as to the progress or state of communication of clinical trials, or other services completed. The Company adjusts its rate of research and development expense recognition if actual results differ from its estimates. The Company makes estimates of its prepaid and accrued expenses as of each balance sheet date in its financial statements based on facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through March 31, 2024, there had been no material adjustments to the Company’s prior period estimates of prepaid and accruals for research and development expenses. The Company’s research and development prepaids and accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors. Basic and Diluted Net Income (Loss) Per Share of Common Stock Basic net income (loss) per share of common stock is computed by dividing net income (loss) by the weighted-average number of shares of common stock outstanding during the period, excluding the dilutive effects of non-vested restricted stock, stock options, and employee stock purchase plan purchase rights. Diluted net income (loss) per share of common stock is computed by dividing net income (loss) by the sum of the weighted-average number of shares of common stock outstanding during the period plus the potential dilutive effects of non-vested restricted stock, stock options, and employee stock purchase plan purchase rights outstanding during the period calculated in accordance with the treasury stock method, but are excluded if their effect is anti-dilutive. Because the impact of these items is anti-dilutive during the periods of net loss, there was no difference between basic and diluted loss per share of common stock for the three months ended March 31, 2024 and 2023. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. In addition to estimates discussed in other sections of this Quarterly Report on Form 10-Q, the most significant estimates in the Company’s consolidated financial statements relate to the valuation of stock options and the valuation allowance for deferred tax assets resulting from net operating losses. These estimates are based on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. Segments The Company operates in only one segment, pharmaceuticals. Impact of Recently Adopted Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which amends the impairment model by requiring entities to use a forward-looking approach on expected losses to estimate credit losses on certain financial instruments, including trade receivables and available-for-sale debt securities. The new guidance was originally due to become effective for the Company beginning in the first quarter of 2020, however the FASB in November 2019 issued ASU 2019-10 which moved the effective date for smaller reporting companies to the first quarter of 2023. The Company adopted ASU 2016-03 as of January 1, 2023. Given the nature of the Company’s receivables and investment portfolio, adoption of this standard had no impact on the Company's financial position, results of operations or cash flows.

Investments

Investments	3 Months Ended
	Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Investments	Investments The following tables summarize the Company’s debt investments (in thousands): March 31, 2024 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Corporate bonds $ 15,331 $ 1 $ (5) $ 15,327 Commercial paper 36,086 13 (12) 36,087 U.S. treasury securities 117,896 26 (201) 117,721 Total investments $ 169,313 $ 40 $ (218) $ 169,135 December 31, 2023 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Corporate bonds $ 11,079 $ 4 $ (7) $ 11,076 Commercial paper 44,271 52 (4) 44,319 U.S. treasury securities 121,474 126 (164) 121,436 Total investments $ 176,824 $ 182 $ (175) $ 176,831 The following tables summarize the Company’s debt investments with unrealized losses, aggregated by investment type and the length of time that individual investments have been in a continuous unrealized loss position (in thousands, except number of securities): March 31, 2024 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 11,047 $ (5) $ — $ — $ 11,047 $ (5) Commercial paper 12,666 (12) — — 12,666 (12) U.S. treasury securities 86,026 (176) 4,969 (25) 90,995 (201) Total $ 109,739 $ (193) $ 4,969 $ (25) $ 114,708 $ (218) Number of securities with unrealized losses 46 2 48 December 31, 2023 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 6,365 $ (7) $ — $ — $ 6,365 $ (7) Commercial paper 5,464 (4) — — 5,464 (4) U.S. treasury securities $ 64,531 $ (120) $ 14,937 $ (44) $ 79,468 $ (164) Total $ 76,360 $ (131) $ 14,937 $ (44) $ 91,297 $ (175) Number of securities with unrealized losses 24 4 28 The Company invests in high credit quality investments in accordance with its investment policy, which is designed to minimize the possibility of loss. The objective of the Company’s investment policy is to ensure the safety and preservation of invested funds, as well as maintaining liquidity sufficient to meet cash flow requirements. The Company places its excess cash with high credit quality financial institutions, commercial companies, and government agencies in order to limit the amount of its credit exposure. In accordance with its policy, the Company is able to invest in marketable debt securities that may consist of U.S. Government and government agency securities, money market and mutual fund investments, certificates of deposits, municipal and corporate notes and bonds, and commercial paper, among others. The Company’s investment policy requires it to purchase high-quality marketable securities with a maximum individual maturity of two years and requires an average portfolio maturity of no more than 12 months. Some of the securities in which the Company invests may have market risk. This means that a change in prevailing interest rates may cause the principal amount of the investment to fluctuate. To minimize this risk, the Company schedules its investments with maturities that coincide with expected cash flow needs, thus avoiding the need to redeem an investment prior to its maturity date. Accordingly, the Company does not believe it has a material exposure to interest rate risk arising from its investments. Generally, the Company’s investments are not collateralized. The Company has not realized any significant losses from its investments. The Company classifies all of its investments as available-for-sale. Unrealized gains and losses on investments are recognized in comprehensive loss, unless an unrealized loss is considered to be other than temporary, in which case the unrealized loss is charged to operations. The Company periodically reviews its investments for other than temporary declines in fair value below cost basis and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. The Company evaluates, among other things, the duration and extent to which the fair value of a security is less than its cost; the financial condition of the issuer and any changes thereto; and the Company’s intent to sell, or whether it will more likely than not be required to sell, the security before recovery of its cost basis. The Company believes the individual unrealized losses represent temporary declines primarily resulting from interest rate changes. Unrealized gains and losses on debt investments are recorded to unrealized gain (loss) on debt investments, net in the Consolidated Statements of Operations and Comprehensive Loss. Realized gains and losses on debt investments are recorded based on specific identification to interest income and other, net in the Consolidated Statements of Operations and Comprehensive Loss. Investments with original maturities at date of purchase beyond three months and which mature at or less than 12 months from the balance sheet date are classified as current investments. Investments with a maturity beyond 12 months from the balance sheet date are classified as long-term investments. At March 31, 2024, the Company believes that the cost of its investments is recoverable in all material respects. The Company recognizes interest income on an accrual basis in interest income in the Consolidated Statements of Operations and Comprehensive Loss. The following table summarizes the scheduled maturity for the Company’s debt investments at March 31, 2024 (in thousands): Maturing in one year or less $ 140,002 Maturing after one year through two years 29,133 Total debt investments $ 169,135

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company leases its facilities under long-term operating leases that expire at various dates through 2026. The Company generally has options to renew lease terms on its facilities, which may be exercised at the Company’s sole discretion. In addition, certain lease arrangements may be terminated prior to their original expiration date at the Company’s discretion. The Company evaluates renewal and termination options at the lease commencement date to determine if it is reasonably certain to exercise the option and has concluded on all operating leases that it is not reasonably certain that any options will be exercised. The weighted-average remaining lease term for the Company’s operating leases as of March 31, 2024 was 2.33 years. Expense related to leases is recorded on a straight-line basis over the lease term. Lease expense under operating leases, including common area maintenance fees, totaled approximately $0.2 million for the three months ended March 31, 2024 and 2023. The discount rate implicit within the Company’s leases is generally not determinable and therefore the Company determines the discount rate based on its incremental borrowing rate based on the information available at commencement date. As of March 31, 2024, the operating lease liabilities reflect a weighted-average discount rate of 7.89%. The following table sets forth the operating lease right-of-use assets and liabilities as of March 31, 2024 (in thousands): Assets Operating lease right-of-use assets $ 1,354 Liabilities Operating lease short-term liabilities (recorded within Accrued liabilities) $ 661 Operating lease long-term liabilities (recorded within Lease-related obligations) 1,005 Total operating lease liabilities $ 1,666 Operating lease payments over the remainder of the lease terms are as follows (in thousands): Years Ending December 31, As of March 31, 2024 2024 572 2025 781 2026 467 Total future minimum rental payments $ 1,820 Less amount of lease payments representing interest 154 Total present value of lease payments $ 1,666 As of December 31, 2023, operating lease payments over the remainder of the lease terms were as follows (in thousands): Years Ending December 31, As of December 31, 2023 2024 759 2025 781 2026 467 Total future minimum rental payments $ 2,007 Less amount of lease payments representing interest 188 Total present value of lease payments $ 1,819 For the three months ended March 31, 2024 and 2023, the Company made lease payments of approximately $0.2 million. Significance of Revenue Source The Company was the recipient of federal research contract funds from BARDA. Periodic audits are required in connection with the Company’s receipt of such funds and certain costs may be questioned as appropriate by BARDA. Accordingly, at March 31, 2024 and December 31, 2023, the Company had recorded a provision for potential refundable amounts of $52,000.

Equity Transactions and Share-b

Equity Transactions and Share-based Compensation	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Equity Transactions and Share-based Compensation	Equity Transactions and Share-based Compensation At-The-Market Equity Offering; Shelf Registration Statement On August 10, 2020, we entered into an Open Market Sale Agreement SM (Prior Jefferies Sales Agreement) with Jefferies LLC, as agent, pursuant to which we may offer and sell, from time to time through Jefferies, up to $75 million of shares of our common stock. As of August 9, 2023, the Form S-3 shelf registration statement that registered the shares of common stock available for sale under the Jefferies Sales Agreement expired at the end of its three-year term, and is no longer available for use. We did not sell any shares of our common stock under the Prior Jefferies Sales Agreement. On February 29, 2024, we terminated the Prior Jefferies Sales Agreement with Jefferies LLC in connection with a new sales agreement by and between Jefferies and us, as discussed below. On May 6, 2021, we filed an automatic shelf registration statement on Form S-3 with the SEC, which was subsequently amended in March 2022 to convert to a non-automatic shelf registration statement. This registration statement enables us to offer for sale, from time to time, in one or more offerings, up to $250 million in the aggregate, of common stock, debt securities, warrants, rights and/or units, and will remain in effect for up to three years from the date it became effective. We have not sold any shares of our securities under the 2021 Shelf Registration Statement. On February 29, 2024, we entered into an Open Market Sale Agreement SM (Jefferies Sales Agreement) with Jefferies LLC, as agent, pursuant to which we may offer and sell, from time to time through Jefferies, up to $75 million of shares of our common stock. On the same day, we filed a shelf registration statement on Form S-3 with the SEC, which contains a base prospectus, covering up to a total aggregate offering price of $250 million of our common stock, preferred stock, debt securities and warrants to purchase any of such securities, and a sales agreement prospectus, covering the offering, issuance and sale of up to a maximum aggregate offering price of $75 million of our common stock that may be issued and sold from time to time under the Jefferies Sales Agreement. The $75 million of shares that may be issued and sold from time to time under the Jefferies Sales Agreement is included in the $250 million of securities that may be offered, issued and sold by us pursuant to our shelf registration statement. As of March 31, 2024, no sales have been made under the shelf registration statement or the Jefferies Sales Agreement. Stock Options The Company maintains a 2013 Equity Incentive Plan (the 2013 Plan), which provides for the grant of incentive stock options (ISOs), non-statutory stock options (NSOs), stock appreciation rights, restricted stock awards, restricted stock unit (RSU) awards, performance-based stock awards, and other forms of equity compensation (collectively, stock awards), all of which may be granted to employees, including officers, non-employee directors and consultants of the Company and its affiliates. Additionally, the 2013 Plan provides for the grant of performance cash awards. The number of shares of common stock reserved for future issuance automatically increased on January 1, 2023, by 4% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, or 3.5 million shares, pursuant to an “evergreen” provision contained in the 2013 Plan commencing on January 1, 2014 and ending on (and including) January 1, 2023. As of March 31, 2024, there was a total of 0.5 million shares reserved for future issuance under the 2013 Plan. The Company issued no shares of common stock pursuant to the exercise of stock options during the three months ended March 31, 2024 and 2023. Employee Stock Purchase Plan The Company maintains a 2013 Employee Stock Purchase Plan (ESPP), which provides for the issuance of shares of common stock pursuant to purchase rights granted to the Company’s employees or to employees of any of its designated affiliates. The Company has reserved a total of 4.8 million shares of common stock to be purchased under the ESPP, of which 1.8 million shares remained available for purchase as of March 31, 2024. The number of shares of common stock reserved for issuance automatically increased on January 1, 2023, by an additional 422,535 shares, pursuant to an “evergreen” provision contained in the ESPP commencing on January 1, 2014 and ending on (and including) January 1, 2023. The ESPP provides for an automatic reset feature to start participants on a new twenty-four-month participation period in the event that the common stock market value on a purchase date is less than the common stock value on the first day of the twenty-four-month offering period. Eligible employees may authorize an amount up to 15% of their salary to purchase common stock at the lower of a 15% discount to the beginning price of their offering period or a 15% discount to the ending price of each six-month purchase interval. The Company issued approximately 419,000 shares of common stock pursuant to the ESPP during the three months ended March 31, 2024. The Company issued approximately 308,000 shares of common stock pursuant to the ESPP during the three months ended March 31, 2023, respectively. Compensation expense for shares purchased under the ESPP related to the purchase discount and the “look-back” option and were determined using a Black-Scholes option pricing model. Restricted Stock Units (RSUs) The Company has issued RSUs to certain employees which vest based on service criteria. When vested, the RSU represents the right to be issued the number of shares of the Company’s common stock that is equal to the number of RSUs granted. The grant date fair value for RSUs is based upon the market price of the Company’s common stock on the date of the grant. The fair value is then amortized to compensation expense over the requisite service period or vesting term. The Company issued approximately 281,000 shares of common stock pursuant to the vesting of RSUs during the three months ended March 31, 2024. The Company issued approximately 221,000 shares of common stock pursuant to the vesting of RSUs during the three months ended March 31, 2023. Share-based Compensation For awards with only service conditions and graded-vesting features, the Company recognizes compensation expense on a straight-line basis over the requisite service period. Total share-based compensation expense recognized related to stock options, the ESPP and RSUs was as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development expense $ 1,870 $ 2,312 General and administrative expense 879 2,051 Total share-based compensation expense $ 2,749 $ 4,363 In December 2022, the Company announced a reduction in workforce. As a result, certain vested stock options were modified to extend their exercise period from 90 days to 12 months. In addition, certain outstanding stock option and RSU grants received accelerated vesting as if the service period of the terminated employee continued for up to an additional 12-month period. The Company recorded expense ratably from the announcement date through the date of termination with approximately $0.4 million being recognized during the twelve months ended December 31, 2022 and an additional $0.6 million being recognized during the three months ended March, 31, 2023. In January 2023, the Company extended the post-termination exercise period from 90 days to three years for stock option grants made to non-employee members of our Board of Directors. This extension applies to all future grants as well as all then-outstanding grants. Related to this extension, the Company recorded approximately $0.3 million of expense during the three months ended March 31, 2023. In November 2023 and April 2024, the Company granted stock options covering up to a total of 950,000 and 223,000 shares, respectively, of our common stock in connection with the hiring of new employees. These grants were non-statutory stock options, have a 10-year term and will vest over four years, with one-fourth vesting on the one-year anniversary of the date of hire and remaining three-fourths vesting over the following three years in equal monthly installments. These stock options are subject to the terms of the Company's 2013 Equity Incentive Plan, but were granted outside of the 2013 Equity Incentive Plan, as they constituted inducement grants in accordance with Nasdaq Stock Market Listing Rule 5635(c)(4).

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company estimates an annual effective tax rate of 0% for the year ending December 31, 2024 as the Company incurred losses for the three month period ended March 31, 2024 and is forecasting an estimated net loss for both financial statement and tax purposes for the year ending December 31, 2024. Therefore, no federal or state income taxes are expected and none have been recorded at this time. Income taxes have been accounted for using the liability method in accordance with FASB ASC 740. Due to the Company's history of cumulative losses since inception, there is not enough evidence at this time to support that the Company will generate future income of a sufficient amount and nature to utilize the benefits of its net deferred tax assets. Accordingly, the deferred tax assets have been reduced by a full valuation allowance, since the Company cannot currently support that realization of its deferred tax assets is more likely than not. However, the Company feels its deferred tax assets may be used upon the Company becoming profitable. At March 31, 2024, the Company had no unrecognized tax benefits that would reduce the Company’s effective tax rate if recognized.

Significant Agreements

Significant Agreements	3 Months Ended
	Mar. 31, 2024
Revenue Recognition [Abstract]
Significant Agreements	Significant Agreements Emergent BioSolutions, Inc. On September 26, 2022, the Company completed the sale to Emergent of the Company’s exclusive worldwide rights to brincidofovir, including TEMBEXA and specified related assets (the Asset Sale). Emergent paid the Company an upfront cash payment of approximately $238 million upon the closing of the Asset Sale. In addition, pursuant to the Asset Purchase Agreement, the Company is eligible to receive from Emergent: (i) up to an aggregate of approximately $124 million in milestone payments payable upon the exercise of the options under the BARDA Agreement for the delivery of up to 1.7 million treatment courses of tablet and suspension formulations of TEMBEXA to the U.S. government; (ii) royalty payments equal to 15% of the gross profits from the sales of TEMBEXA made outside of the United States; (iii) royalty payments equal to 20% of the gross profits from the sales of TEMBEXA made in the United States in excess of 1.7 million treatment courses; and (iv) up to an additional $12.5 million upon the achievement of certain other developmental milestones. The effects of recording certain adjustments associated with contingent consideration related to TEMBEXA have been excluded as the Company has made a policy election to account for these amounts when the contingency has been resolved in accordance with Accounting Standards Codification 450, Contingencies . The period under which the Company was contracted to provide the majority of operational support services to Emergent in furtherance of its obligations under the Asset Purchase Agreement and the BARDA Agreement concluded on March 26, 2023, except for certain services which the parties agreed would continue until the occurrence of a specific event, or in some cases a predetermined end date. The BARDA Agreement was novated to Emergent in December 2022. The Company recognized no contract revenue for support provided for the three months ended March 31, 2024. The Company recognized $0.2 million of contract revenue for support provided to Emergent for the three months ended March 31, 2023. Ohara Agreement In 2019, Oncoceutics, Inc., a Delaware corporation (Oncoceutics) which was subsequently acquired by the Company in January 2021, entered into a license, development and commercialization agreement with Ohara Pharmaceutical Co., Ltd. for dordaviprone in Japan. The Company is entitled to receive up to $2.5 million in nonrefundable regulatory milestone payments. The Company is entitled to double-digit tiered royalties based on the aggregate annual net sales of all products, as defined in the agreement, in Japan. CR Sanjiu Agreement

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2024
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company has evaluated subsequent events through the issuance date of these financial statements to ensure that this filing includes appropriate disclosure of events both recognized in the financial statements as of March 31, 2024, and events which occurred subsequently but were not recognized in the financial statements.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net loss	$ (21,869)	$ (21,372)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	Our officers (as defined in Rule 16a-1(f) under the Exchange Act) other than Thomas J. Riga, Chief Operating and Commercial Officer, have entered into sell-to-cover arrangements adopted pursuant to Rule 10b5-1 authorizing the pre-arranged sale of shares to satisfy tax withholding obligations of the Company arising exclusively from the vesting of time-vesting restricted stock units and the related issuance of shares. The amount of shares to be sold to satisfy the Company’s tax withholding obligations under these arrangements is dependent on future events which cannot be known at this time, including the future trading price of Company shares. The expiration date relating to these arrangements is dependent on future events which cannot be known at this time, including the final vest date of the applicable time-vesting restricted stock units and the officer’s termination of service.
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Officer Trading Arrangement [Member]
Trading Arrangements, by Individual
Title	officers
Rule 10b5-1 Arrangement Adopted	true

The Business and Summary of S_2

The Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of certain financial instruments, including accounts receivable, accounts payable and accrued expenses approximate their fair values due to the short-term nature of such instruments. For assets and liabilities recorded at fair value, it is the Company’s policy to maximize the use of observable inputs and minimize the use of unobservable inputs when developing fair value measurements, in accordance with the fair value hierarchy. Fair value measurements for assets and liabilities where there exists limited or no observable market data are based primarily upon estimates and are often calculated based on the economic and competitive environment, the characteristics of the asset or liability and other factors. Therefore, fair value measurements cannot be determined with precision and may not be realized in an actual sale or immediate settlement of the asset or liability. Additionally, there may be inherent weaknesses in any calculation technique and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the calculated current or future fair values. The Company utilizes fair value measurements to record fair value adjustments to certain assets and liabilities and to determine fair value disclosures. The Company groups assets and liabilities at fair value in three levels, based on the markets in which the assets and liabilities are traded and the reliability of the assumptions used to determine fair value. The determination of where an asset or liability falls in the hierarchy requires significant judgment. These levels are: • Level 1 — Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. • Level 2 — Valuations based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and models for which all significant inputs are observable, either directly or indirectly. • Level 3 — Valuations based on inputs that are unobservable and significant to the overall fair value measurement. There was no material re-measurement to fair value of financial assets and liabilities that are not measured at fair value on a recurring basis. For additional information regarding the Company’s investments, please refer to Note 2, “Investments.”
Revenue Recognition	Revenue Recognition Policy The Company’s revenues generally consist of (i) contract and grant revenue—revenue generated under federal and private foundation grants and contracts, (ii) licensing revenue—revenue related to non-refundable upfront fees, royalties and milestone payments earned under license agreements and (iii) royalty revenue—revenue related to sales of TEMBEXA made by Emergent after the Asset Sale. Revenue is recognized in accordance with the criteria outlined in Accounting Standards Codification (ASC) 606 issued by the Financial Accounting Standards Board (FASB). Following this accounting pronouncement, a five-step approach is applied for recognizing revenue, including (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when, or as, the entity satisfies a performance obligation.
Research and Development Prepaids and Accruals	Research and Development Prepaids and Accruals As part of the process of preparing financial statements, the Company is required to estimate its expenses resulting from its obligation under contracts with vendors and consultants and clinical site agreements in connection with its research and development efforts. The financial terms of these contracts are subject to negotiations which vary contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate research and development expenses in its financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of its research and development efforts. The Company determines prepaid and accrual estimates through discussion with applicable personnel and outside service providers as to the progress or state of communication of clinical trials, or other services completed. The Company adjusts its rate of research and development expense recognition if actual results differ from its estimates. The Company makes estimates of its prepaid and accrued expenses as of each balance sheet date in its financial statements based on facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through March 31, 2024, there had been no material adjustments to the Company’s prior period estimates of prepaid and accruals for research and development expenses. The Company’s research and development prepaids and accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors.
Basic and Diluted Net Income (Loss) Per Share of Common Stock	Basic and Diluted Net Income (Loss) Per Share of Common Stock
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. In addition to estimates discussed in other sections of this Quarterly Report on Form 10-Q, the most significant estimates in the Company’s consolidated financial statements relate to the valuation of stock options and the valuation allowance for deferred tax assets resulting from net operating losses. These estimates are based on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates.
Segments	Segments
Impact of Recently Adopted Accounting Standards	Impact of Recently Adopted Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which amends the impairment model by requiring entities to use a forward-looking approach on expected losses to estimate credit losses on certain financial instruments, including trade receivables and available-for-sale debt securities. The new guidance was originally due to become effective for the Company beginning in the first quarter of 2020, however the FASB in November 2019 issued ASU 2019-10 which moved the effective date for smaller reporting companies to the first quarter of 2023. The Company adopted ASU 2016-03 as of January 1, 2023. Given the nature of the Company’s receivables and investment portfolio, adoption of this standard had no impact on the Company's financial position, results of operations or cash flows.

The Business and Summary of S_3

The Business and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Schedule of Certain Assets Measured at Fair Value on a Recurring Basis	Below are tables that present information about certain assets measured at fair value on a recurring basis (in thousands): Fair Value Measurements March 31, 2024 Total Quoted Prices in Significant Other Significant Cash equivalents Money market funds $ 10,625 $ 10,625 $ — $ — Total cash equivalents 10,625 10,625 — — Short-term investments U.S. treasury securities 88,588 46,325 42,263 — Commercial paper 36,087 — 36,087 — Corporate bonds 15,327 — 15,327 — Total short-term investments 140,002 46,325 93,677 — Long-term investments U.S. treasury securities 29,133 5,959 23,174 — Total long-term investments 29,133 5,959 23,174 — Total assets $ 179,760 $ 62,909 $ 116,851 $ — Fair Value Measurements December 31, 2023 Total Quoted Prices in Significant Other Significant Cash equivalents Money market funds $ 24,102 $ 24,102 $ — $ — Total cash equivalents 24,102 24,102 — — Short-term investments U.S. treasury securities 99,779 40,336 59,443 — Commercial paper 44,319 — 44,319 — Corporate bonds 11,076 — 11,076 — Total short-term investments 155,174 40,336 114,838 — Long-term investments U.S. treasury securities 21,657 3,975 17,682 — Total long-term investments 21,657 3,975 17,682 — Total assets $ 200,933 $ 68,413 $ 132,520 $ —
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): March 31, 2024 December 31, 2023 Accrued research and development expenses $ 9,445 $ 7,623 Accrued compensation 2,810 5,123 Other accrued liabilities 2,857 2,846 Total accrued liabilities $ 15,112 $ 15,592

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Schedule of Short-Term and Long-Term Investments	The following tables summarize the Company’s debt investments (in thousands): March 31, 2024 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Corporate bonds $ 15,331 $ 1 $ (5) $ 15,327 Commercial paper 36,086 13 (12) 36,087 U.S. treasury securities 117,896 26 (201) 117,721 Total investments $ 169,313 $ 40 $ (218) $ 169,135 December 31, 2023 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Corporate bonds $ 11,079 $ 4 $ (7) $ 11,076 Commercial paper 44,271 52 (4) 44,319 U.S. treasury securities 121,474 126 (164) 121,436 Total investments $ 176,824 $ 182 $ (175) $ 176,831
Schedule of Investments with Unrealized Losses, Aggregated by Investment Type and the Length of Time	The following tables summarize the Company’s debt investments with unrealized losses, aggregated by investment type and the length of time that individual investments have been in a continuous unrealized loss position (in thousands, except number of securities): March 31, 2024 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 11,047 $ (5) $ — $ — $ 11,047 $ (5) Commercial paper 12,666 (12) — — 12,666 (12) U.S. treasury securities 86,026 (176) 4,969 (25) 90,995 (201) Total $ 109,739 $ (193) $ 4,969 $ (25) $ 114,708 $ (218) Number of securities with unrealized losses 46 2 48 December 31, 2023 Less than 12 Months Greater than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate bonds $ 6,365 $ (7) $ — $ — $ 6,365 $ (7) Commercial paper 5,464 (4) — — 5,464 (4) U.S. treasury securities $ 64,531 $ (120) $ 14,937 $ (44) $ 79,468 $ (164) Total $ 76,360 $ (131) $ 14,937 $ (44) $ 91,297 $ (175) Number of securities with unrealized losses 24 4 28
Schedule of the Scheduled Maturity of Company Investments	The following table summarizes the scheduled maturity for the Company’s debt investments at March 31, 2024 (in thousands): Maturing in one year or less $ 140,002 Maturing after one year through two years 29,133 Total debt investments $ 169,135

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Schedule of Operating Lease Right-of-Use Assets and Liabilities	The following table sets forth the operating lease right-of-use assets and liabilities as of March 31, 2024 (in thousands): Assets Operating lease right-of-use assets $ 1,354 Liabilities Operating lease short-term liabilities (recorded within Accrued liabilities) $ 661 Operating lease long-term liabilities (recorded within Lease-related obligations) 1,005 Total operating lease liabilities $ 1,666
Schedule of Operating Lease Maturity	Operating lease payments over the remainder of the lease terms are as follows (in thousands): Years Ending December 31, As of March 31, 2024 2024 572 2025 781 2026 467 Total future minimum rental payments $ 1,820 Less amount of lease payments representing interest 154 Total present value of lease payments $ 1,666 As of December 31, 2023, operating lease payments over the remainder of the lease terms were as follows (in thousands): Years Ending December 31, As of December 31, 2023 2024 759 2025 781 2026 467 Total future minimum rental payments $ 2,007 Less amount of lease payments representing interest 188 Total present value of lease payments $ 1,819

Equity Transactions and Share_2

Equity Transactions and Share-based Compensation (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Employee and Non-Employee Share-Based Compensation Expense Recognized Related to Stock Options, the ESPP and RSUs	Total share-based compensation expense recognized related to stock options, the ESPP and RSUs was as follows (in thousands): Three Months Ended March 31, 2024 2023 Research and development expense $ 1,870 $ 2,312 General and administrative expense 879 2,051 Total share-based compensation expense $ 2,749 $ 4,363

The Business and Summary of S_4

The Business and Summary of Significant Accounting Policies - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Separate Account Investment
Short-term investments	$ 140,002	$ 155,174
Total long-term investments	29,133	21,657
Fair value, Measurements, Recurring
Fair Value, Separate Account Investment
Cash equivalents	10,625	24,102
Short-term investments	140,002	155,174
Total long-term investments	29,133	21,657
Total assets	179,760	200,933
Fair value, Measurements, Recurring | U.S. treasury securities
Fair Value, Separate Account Investment
Short-term investments	88,588	99,779
Total long-term investments	29,133	21,657
Fair value, Measurements, Recurring | Commercial paper
Fair Value, Separate Account Investment
Short-term investments	36,087	44,319
Fair value, Measurements, Recurring | Corporate bonds
Fair Value, Separate Account Investment
Short-term investments	15,327	11,076
Fair value, Measurements, Recurring | Money market funds
Fair Value, Separate Account Investment
Cash equivalents	10,625	24,102
Fair value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Separate Account Investment
Cash equivalents	10,625	24,102
Short-term investments	46,325	40,336
Total long-term investments	5,959	3,975
Total assets	62,909	68,413
Fair value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasury securities
Fair Value, Separate Account Investment
Short-term investments	46,325	40,336
Total long-term investments	5,959	3,975
Fair value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial paper
Fair Value, Separate Account Investment
Short-term investments	0	0
Fair value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
Fair Value, Separate Account Investment
Short-term investments	0	0
Fair value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Fair Value, Separate Account Investment
Cash equivalents	10,625	24,102
Fair value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Separate Account Investment
Cash equivalents	0	0
Short-term investments	93,677	114,838
Total long-term investments	23,174	17,682
Total assets	116,851	132,520
Fair value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. treasury securities
Fair Value, Separate Account Investment
Short-term investments	42,263	59,443
Total long-term investments	23,174	17,682
Fair value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Commercial paper
Fair Value, Separate Account Investment
Short-term investments	36,087	44,319
Fair value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate bonds
Fair Value, Separate Account Investment
Short-term investments	15,327	11,076
Fair value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Money market funds
Fair Value, Separate Account Investment
Cash equivalents	0	0
Fair value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Separate Account Investment
Cash equivalents	0	0
Short-term investments	0	0
Total long-term investments	0	0
Total assets	0	0
Fair value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | U.S. treasury securities
Fair Value, Separate Account Investment
Short-term investments	0	0
Total long-term investments	0	0
Fair value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Commercial paper
Fair Value, Separate Account Investment
Short-term investments	0	0
Fair value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate bonds
Fair Value, Separate Account Investment
Short-term investments	0	0
Fair value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Money market funds
Fair Value, Separate Account Investment
Cash equivalents	$ 0	$ 0

The Business and Summary of S_5

The Business and Summary of Significant Accounting Policies - Employee Retention Credit (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2022
Business and Summary of Significant Accounting Policies
Employee retention credit			$ 2,000
Research and development	$ (18,844)	$ (18,822)
General and administrative	(5,546)	$ (5,679)
Proceeds from tax refund	$ 1,800
Scenario, Adjustment
Business and Summary of Significant Accounting Policies
Research and development			1,500
General and administrative			$ 500

The Business and Summary of S_6

The Business and Summary of Significant Accounting Policies - Deferred Loan Costs (Details) - Revolving Credit Facility	Nov. 21, 2023	Jan. 31, 2022 USD ($) installment	Mar. 31, 2024 USD ($)
Business and Summary of Significant Accounting Policies
Debt instrument, term (in years)		4 years
Aggregate principal amount		$ 50,000,000
Line of credit facility, unused capacity, commitment fee (as a percent)	0.35%	0.35%
Debt instrument, interest rate, stated (as a percent)		4.75%
Debt instrument, early termination fee		$ 500,000
Debt instrument, unused borrowing capacity, fee		$ 500,000
Number of installment payments (installment) | installment		4
Current deferred loan costs			$ 100,000
Noncurrent deferred loan costs			200,000
Loan fee liability			$ 200,000
Prime Rate
Business and Summary of Significant Accounting Policies
Debt instrument, basis spread on variable rate (as a percent)		1.50%

The Business and Summary of S_7

The Business and Summary of Significant Accounting Policies - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accounting Policies [Abstract]
Accrued research and development expenses	$ 9,445	$ 7,623
Accrued compensation	2,810	5,123
Other accrued liabilities	2,857	2,846
Total accrued liabilities	$ 15,112	$ 15,592

The Business and Summary of S_8

The Business and Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands		3 Months Ended
	Sep. 26, 2022 USD ($) treatment	Mar. 31, 2024 USD ($) segment	Mar. 31, 2023 USD ($)	Dec. 31, 2019 USD ($)
Business and Summary of Significant Accounting Policies
Contract and grant revenue		$ 0	$ 283
Number of segment | segment		1
Grant | Oncoceutics, Inc.
Business and Summary of Significant Accounting Policies
Deferred revenue		$ 100
Contract and grant revenue		0	30
Licensing
Business and Summary of Significant Accounting Policies
Contract and grant revenue		0	49
SymBio Pharmaceuticals | Scenario, Plan
Business and Summary of Significant Accounting Policies
Deferred revenue	$ 12,500
Emergent Biodefense Operations Lansing LLC
Business and Summary of Significant Accounting Policies
Revenue recognized		0	200
Ohara Pharmaceutical Co., Ltd.
Business and Summary of Significant Accounting Policies
License agreement, nonrefundable regulatory milestone payment to be received				$ 2,500
Ohara Pharmaceutical Co., Ltd. | Licensing
Business and Summary of Significant Accounting Policies
Contract and grant revenue		$ 0	$ 100
Base Period | Emergent | TEMBEXA
Business and Summary of Significant Accounting Policies
Up-front cash payment	$ 238,000
Quantity royalty rate, trigger (treatments) | treatment	1,700,000
Base Period | Emergent | TEMBEXA | Non- United States
Business and Summary of Significant Accounting Policies
Gross profit royalty rate (as a percent)	15%
Base Period | Emergent | TEMBEXA | United States
Business and Summary of Significant Accounting Policies
Gross profit royalty rate (as a percent)	20%
Base Period | Emergent | BARDA
Business and Summary of Significant Accounting Policies
Maximum milestone proceeds upon the exercise of options	$ 124,000

Investments - Schedule of Avail

Investments - Schedule of Available-for-Sale securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Schedule of Investments
Amortized Cost	$ 169,313	$ 176,824
Gross Unrealized Gains	40	182
Gross Unrealized Losses	(218)	(175)
Estimated Fair Value	169,135	176,831
Corporate bonds
Schedule of Investments
Amortized Cost	15,331	11,079
Gross Unrealized Gains	1	4
Gross Unrealized Losses	(5)	(7)
Estimated Fair Value	15,327	11,076
Commercial paper
Schedule of Investments
Amortized Cost	36,086	44,271
Gross Unrealized Gains	13	52
Gross Unrealized Losses	(12)	(4)
Estimated Fair Value	36,087	44,319
U.S. treasury securities
Schedule of Investments
Amortized Cost	117,896	121,474
Gross Unrealized Gains	26	126
Gross Unrealized Losses	(201)	(164)
Estimated Fair Value	$ 117,721	$ 121,436

Investments - Schedule of Inves

Investments - Schedule of Investments with Unrealized Losses, Aggregated by Investment Type and the Length of Time (Details) $ in Thousands	Mar. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Debt Securities, Available-for-sale
Fair value, less than 12 months	$ 109,739	$ 76,360
Unrealized loss, less than 12 months	(193)	(131)
Fair value, greater than 12 months	4,969	14,937
Unrealized loss, greater than 12 months	(25)	(44)
Fair value, total	114,708	91,297
Unrealized loss, total	$ (218)	$ (175)
Number of securities with unrealized losses, less than 12 months | security	46	24
Number of securities with unrealized losses, greater than 12 months | security	2	4
Number of securities with unrealized losses, total | security	48	28
Corporate bonds
Debt Securities, Available-for-sale
Fair value, less than 12 months	$ 11,047	$ 6,365
Unrealized loss, less than 12 months	(5)	(7)
Fair value, greater than 12 months	0	0
Unrealized loss, greater than 12 months	0	0
Fair value, total	11,047	6,365
Unrealized loss, total	(5)	(7)
Commercial paper
Debt Securities, Available-for-sale
Fair value, less than 12 months	12,666	5,464
Unrealized loss, less than 12 months	(12)	(4)
Fair value, greater than 12 months	0	0
Unrealized loss, greater than 12 months	0	0
Fair value, total	12,666	5,464
Unrealized loss, total	(12)	(4)
U.S. treasury securities
Debt Securities, Available-for-sale
Fair value, less than 12 months	86,026	64,531
Unrealized loss, less than 12 months	(176)	(120)
Fair value, greater than 12 months	4,969	14,937
Unrealized loss, greater than 12 months	(25)	(44)
Fair value, total	90,995	79,468
Unrealized loss, total	$ (201)	$ (164)

Investments - Schedule of Inv_2

Investments - Schedule of Investment Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value
Maturing in one year or less	$ 140,002
Maturing after one year through two years	29,133
Total debt investments	$ 169,135	$ 176,831

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Disaggregation of Revenue
Weighted average remaining lease term (in years)	2 years 3 months 29 days
Rent expense under non-cancelable operating leases	$ 200	$ 200
Weighted average discount rate (as a percent)	7.89%
Lease payments	$ 200	$ 200
BARDA | Refundable Agreements
Disaggregation of Revenue
Provision for refundable amounts	$ 52		$ 52

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Operating Lease Right-of-Use Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets
Operating lease right-of-use assets	$ 1,354	$ 1,482
Liabilities
Operating lease short-term liabilities (recorded within Accrued liabilities)	661
Operating lease long-term liabilities (recorded within Lease-related obligations)	1,005	1,177
Total operating lease liabilities	$ 1,666	$ 1,819
Operating lease, liability, current, statement of financial position [extensible list]	Accrued Liabilities, Current

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Maturity Analysis of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Lessee, Operating Lease, Liability, Payment, Due
Remainder of fiscal year	$ 572
Year one	781	$ 759
Year two	467	781
Year three		467
Total future minimum rental payments	1,820	2,007
Less amount of lease payments representing interest	154	188
Total present value of lease payments	$ 1,666	$ 1,819

Equity Transactions and Share_3

Equity Transactions and Share-based Compensation - Narrative (Details) - USD ($)			1 Months Ended		3 Months Ended		12 Months Ended
	Jan. 01, 2023	Aug. 10, 2020	Apr. 30, 2024	Nov. 30, 2023	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2022	Feb. 29, 2024	Mar. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award
Shares issued for restricted stock units (in shares)					281,000	221,000
One-time employee termination benefits						$ 600,000	$ 400,000
Share-based payment arrangement, expense					$ 2,749,000	4,363,000
Independent Members Of Board
Share-based Compensation Arrangement by Share-based Payment Award
Share-based payment arrangement, expense						$ 300,000
New employees
Share-based Compensation Arrangement by Share-based Payment Award
Options granted (in shares)				950,000
New employees | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Options granted (in shares)			223,000
New employees | Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award
Expiration period					10 years
Vesting period					4 years
The 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award
Evergreen option provision, equity increase (as a percent)	4%
Additional shares authorized (in shares)	3,500,000
Number of shares reserved for future issuance (in shares)					500,000
Shares issued pursuant to the exercise of stock options (in shares)					0	0
The 2013 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Additional shares authorized (in shares)	422,535
Number of shares reserved for future issuance (in shares)					1,800,000
Number of shares authorized to be granted (in shares)					4,800,000
Participation term (in months)					24 months
Percentage of pay that employee can contribute, maximum (as a percent)					15%
Discounted purchase price from market price, offering date (as a percent)					15%
Discounted purchase price from market price, purchase date (as a percent)					15%
Purchase interval (in months)					6 months
Shares issued pursuant to employee stock purchase plan (in shares)					419,000	308,000
Public Offering
Share-based Compensation Arrangement by Share-based Payment Award
Sale of common stock, amount authorized		$ 75,000,000						$ 250,000,000	$ 250,000,000
Sales of stock, exercise term (in years)		3 years
Sales of stock, authorization term (in years)									3 years
Public Offering | Jeffries LLC
Share-based Compensation Arrangement by Share-based Payment Award
Sale of common stock, amount authorized								$ 75,000,000

Equity Transactions and Share_4

Equity Transactions and Share-based Compensation - Schedule of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Payment Arrangement, Expensed and Capitalized, Amount
Total share-based compensation expense	$ 2,749	$ 4,363
Research and development expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount
Total share-based compensation expense	1,870	2,312
General and administrative expense
Share-based Payment Arrangement, Expensed and Capitalized, Amount
Total share-based compensation expense	$ 879	$ 2,051

Income Taxes (Details)

Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Mar. 31, 2024
Income Tax Contingency
Unrecognized tax benefits		$ 0
Scenario, Forecast
Income Tax Contingency
Estimated annual effective tax rate (as a percent)	0%

Significant Agreements (Details

Significant Agreements (Details) $ in Thousands		3 Months Ended
	Sep. 26, 2022 USD ($) treatment	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Emergent | TEMBEXA | Base Period
Schedule of Investments
Up-front cash payment	$ 238,000
Quantity royalty rate, trigger (treatments) | treatment	1,700,000
Emergent | TEMBEXA | Base Period | Non- United States
Schedule of Investments
Gross profit royalty rate (as a percent)	15%
Emergent | TEMBEXA | Base Period | United States
Schedule of Investments
Gross profit royalty rate (as a percent)	20%
Emergent | BARDA | Base Period
Schedule of Investments
Maximum milestone proceeds upon the exercise of options	$ 124,000
SymBio Pharmaceuticals | Scenario, Plan
Schedule of Investments
Deferred revenue	$ 12,500
Emergent Biodefense Operations Lansing LLC
Schedule of Investments
Revenue recognized		$ 0	$ 200
Ohara Pharmaceutical Co., Ltd.
Schedule of Investments
License agreement, nonrefundable regulatory milestone payment to be received					$ 2,500
CR Sanjui | Oncoceutics, Inc.
Schedule of Investments
Payment to be received upon achievement of milestones				$ 5,000