Regulus Therapeutics (RGLS) 10-Q 12 May 22 2022 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2022	May 06, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2022
Document Transition Report	false
Entity File Number	001-35670
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-4738379
Entity Address, Address Line One	4224 Campus Point Court, Suite 210
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	202-6300
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	RGLS
Security Exchange Name	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		145,981,180
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Entity Registrant Name	REGULUS THERAPEUTICS INC.
Entity Central Index Key	0001505512
Current Fiscal Year End Date	--12-31

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 53,902	$ 60,383
Restricted cash	62	62
Contract and other receivables	8	0
Prepaid materials, net	3,010	3,010
Prepaid expenses and other current assets	951	1,780
Total current assets	57,933	65,235
Property and equipment, net	394	281
Intangibles, net	74	83
Right of use asset	2,436	2,564
Other assets	148	291
Total assets	60,985	68,454
Current liabilities:
Accounts payable	625	285
Accrued liabilities	827	821
Accrued research and development expenses	608	810
Accrued compensation	858	2,016
Current portion of term loan, less debt issuance costs	826	0
Other current liabilities	957	1,295
Total current liabilities	4,701	5,227
Term loan, less debt issuance costs	3,588	4,673
Lease liability, less current portion	2,262	2,417
Other long-term liabilities	1,193	1,179
Total liabilities	11,744	13,496
Commitments and Contingencies	0	0
Stockholders’ equity:
Common stock, $0.001 par value; 400,000,000 shares authorized at March 31, 2022 and December 31, 2021; 145,981,180 and 145,971,184 shares issued and outstanding at March 31, 2022 (unaudited) and December 31, 2021, respectively	146	146
Additional paid-in capital	510,662	509,660
Accumulated deficit	(461,572)	(454,853)
Total stockholders’ equity	49,241	54,958
Total liabilities and stockholders’ equity	60,985	68,454
Class A-1 Convertible Preferred Stock
Stockholders’ equity:
Preferred stock	0	0
Class A-2 Convertible Preferred Stock
Stockholders’ equity:
Preferred stock	1	1
Class A-3 Convertible Preferred Stock
Stockholders’ equity:
Preferred stock	0	0
Class A-4 Convertible Preferred Stock
Stockholders’ equity:
Preferred stock	$ 4	$ 4

CONDENSED BALANCE SHEETS (Paren

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Common stock par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	400,000,000
Common stock, shares issued (in shares)	145,981,180	145,971,184
Common stock, shares outstanding (in shares)	145,981,180	145,971,184
Class A-1 Convertible Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	256,700	256,700
Preferred stock, shares issued (in shares)	256,700	256,700
Preferred stock, shares outstanding (in shares)	256,700	256,700
Class A-2 Convertible Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	1,330,832	1,330,832
Preferred stock, shares issued (in shares)	1,330,832	1,330,832
Preferred stock, shares outstanding (in shares)	1,330,832	1,330,832
Class A-3 Convertible Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	258,707	258,707
Preferred stock, shares issued (in shares)	258,707	258,707
Preferred stock, shares outstanding (in shares)	258,707	258,707
Class A-4 Convertible Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	3,725,720	3,725,720
Preferred stock, shares issued (in shares)	3,725,720	3,725,720
Preferred stock, shares outstanding (in shares)	3,725,720	3,725,720

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating expenses:
Research and development	$ 3,679	$ 3,320
General and administrative	2,890	2,478
Total operating expenses	6,569	5,798
Loss from operations	(6,569)	(5,798)
Other income (expense):
Interest and other income	6	1
Interest and other expense	(155)	(216)
Loss before income taxes	(6,718)	(6,013)
Income tax expense	(1)	0
Net loss and comprehensive loss	$ (6,719)	$ (6,013)
Net loss per share, basic (in usd per share)	$ (0.05)	$ (0.08)
Net loss per share, diluted (in usd per share)	$ (0.05)	$ (0.08)
Weighted average shares used to compute basic net loss per share (in shares)	145,973,989	71,290,918
Weighted average shares used to compute diluted net loss per share (in shares)	145,973,989	71,290,918

CONDENSED STATEMENTS OF CHANGES

CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated deficit	Convertible preferred stockPreferred Stock
Beginning balance (in shares) at Dec. 31, 2020		67,432,712			1,931,860
Beginning balance at Dec. 31, 2020	$ 26,026	$ 67	$ 453,002	$ (427,045)	$ 2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon vesting of restricted stock units (in shares)		16,902
Issuance of common stock upon exercise of options (in shares)		26,770
Issuance of common stock upon exercise of options	26		26
Issuance of common stock upon exercise of warrants (in shares)		2,418,681
Issuance of common stock upon exercise of warrants	666	$ 3	663
Issuance of common stock through ATM (in shares)		4,009,585
Issuance of common stock through ATM	5,713	$ 4	5,709
Issuance of common stock under Employee Stock Purchase Plan (in shares)		4,122
Issuance of common stock under Employee Stock Purchase Plan	2		2
Conversions of convertible preferred stock (in shares)		780,360			(78,036)
Conversions of convertible preferred stock	0	$ 1	(1)
Stock-based compensation expense	691		691
Net loss	(6,013)			(6,013)
Ending balance (in shares) at Mar. 31, 2021		74,689,132			1,853,824
Ending balance at Mar. 31, 2021	27,111	$ 75	460,092	(433,058)	$ 2
Beginning balance (in shares) at Dec. 31, 2021		145,971,184			5,571,959
Beginning balance at Dec. 31, 2021	54,958	$ 146	509,660	(454,853)	$ 5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)		9,996
Issuance of common stock under Employee Stock Purchase Plan	2		2
Stock-based compensation expense	1,000		1,000
Net loss	(6,719)			(6,719)
Ending balance (in shares) at Mar. 31, 2022		145,981,180			5,571,959
Ending balance at Mar. 31, 2022	$ 49,241	$ 146	$ 510,662	$ (461,572)	$ 5

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (6,719)	$ (6,013)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization expense	26	335
Stock-based compensation	1,000	691
Other	38	10
Change in operating assets and liabilities:
Contracts and other receivables	(8)	432
Prepaid expenses and other assets	681	356
Accounts payable	340	275
Accrued liabilities	(26)	14
Accrued research and development expenses	(202)	(371)
Accrued compensation	(1,159)	(941)
Operating lease right-of-use assets and liabilities, net	(12)	90
Other liabilities	(340)	(589)
Net cash used in operating activities	(6,381)	(5,711)
Investing activities
Purchases of property and equipment	(102)	(53)
Net cash used in investing activities	(102)	(53)
Financing activities
Proceeds from issuance of common stock, net	2	6,382
Proceeds from exercise of common stock options	0	26
Payments on financing leases	0	(72)
Net cash provided by financing activities	2	6,336
Net (decrease) increase in cash and cash equivalents	(6,481)	572
Cash and cash equivalents at beginning of period	60,445	31,087
Cash and cash equivalents at end of period	53,964	31,659
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	53,902	31,597
Restricted cash	62	62
Total cash, cash equivalents and restricted cash	53,964	31,659
Supplemental disclosure of cash flow information
Interest paid	(110)	(109)
Income taxes paid	(1)	0
Supplemental disclosure of non-cash investing and financing activities
Non-cash acquisition of property and equipment	$ 33	$ 24

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and 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. In management’s opinion, the accompanying financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented. Interim financial results are not necessarily indicative of results anticipated for the full year. These unaudited condensed financial statements should be read in conjunction with the audited financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2021, from which the balance sheet information herein was derived. Liquidity Through the date of the issuance of these financial statements, we have principally been financed through proceeds received from the sale of our common stock and other equity securities, debt financings, up-front payments and milestones received from collaboration agreements, totaling $538.0 million. As of March 31, 2022, we had approximately $53.9 million of cash and cash equivalents. We are in compliance with all Loan Agreement covenants. We intend to seek additional capital through equity and/or debt financings, collaborative or other funding arrangements with partners or through other sources of financing. Should we seek additional financing from outside sources, we may not be able to raise such financing on terms acceptable to us or at all. If we are unable to raise additional capital when required or on acceptable terms, we may be required to scale back or discontinue the advancement of product candidates, reduce headcount, file for bankruptcy, reorganize, merge with another entity, or cease operations. Use of Estimates Our condensed financial statements are prepared in accordance with GAAP, which requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in our financial statements and accompanying notes. An estimated loss contingency is accrued in our financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Although these estimates are based on our knowledge of current events and actions we may undertake in the future, actual results may ultimately differ from these estimates and assumptions. Additionally, the impact of the COVID-19 pandemic to our business and operating results presents additional uncertainty. Stock-Based Compensation We account for stock-based compensation expense related to stock options granted to employees and members of our board of directors by estimating the fair value of each stock option on the date of grant using the Black-Scholes option pricing model. We recognize stock-based compensation expense using the accelerated multiple-option approach. Under the accelerated multiple-option approach (also known as the graded-vesting method), we recognize compensation expense over the requisite service period for each separately vesting tranche of the award as though the award was in substance multiple awards, resulting in accelerated expense recognition over the vesting period. For performance-based awards granted to employees (i) the fair value of the award is determined on the grant date, (ii) we assess the probability of the individual milestones under the award being achieved and (iii) the fair value of the shares subject to the milestone is expensed over the implicit service period commencing once management believes the performance criteria is probable of being met. We account for restricted stock units by determining the fair value of each restricted stock unit based on the closing market price of our common stock on the date of grant. We recognize stock-based compensation expense using the accelerated multiple-option approach over the requisite service periods of the awards, and forfeitures are recognized as they occur. Clinical Trial and Preclinical Study Accruals We make estimates of our accrued expenses for clinical trial and preclinical study activities as of each balance sheet date in our financial statements based on the facts and circumstances known to us at that time. These accruals are based upon estimates of costs incurred and fees that may be associated with services provided by clinical trial investigational sites and CROs and for other clinical trial-related activities. Payments under certain contracts with such parties depend on factors such as successful enrollment of patients, site initiation and the completion of clinical trial milestones. In accruing for these services, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If possible, we obtain information regarding unbilled services directly from these service providers. However, we may be required to estimate these services based on other information available to us. If we underestimate or overestimate the activities or fees associated with a study or service at a given point in time, adjustments to research and development expenses may be necessary in future periods. Historically, our estimated accrued liabilities have approximated actual expense incurred. Subsequent changes in estimates may result in a material change in our accruals. Prepaid Materials We capitalize the purchase of certain raw materials and related supplies for use in the manufacturing of drug product in our preclinical and clinical development programs, as we have determined that these materials have alternative future use. We can use these raw materials and related supplies in multiple clinical drug products, and therefore these raw materials have future use independent of the development status of any particular drug program until it is utilized in the manufacturing process. We expense the cost of materials when used. We periodically review these capitalized materials for continued alternative future use and write down the asset to its net realizable value in the period in which an impairment is identified. Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . Subsequently, in November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments-Credit Losses . ASU 2016-13 requires entities to measure all expected credit losses for most financial assets held at the reporting date based on an expected loss model which includes historical experience, current conditions, an d reasonable and supportable forecasts. ASU 2016-13 also requires enhanced disclosures to help financial statement users better understand significant estimates and judgments used in estimating credit losses. This ASU is effective for smaller reporting companies for fiscal years beginning after December 15, 2022, with early adoption permitted. We are assessing the impact this standard will have on our financial statements and disclosures. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848),

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per ShareBasic net loss per share is calculated by dividing net loss by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method or if-converted method. Dilutive common stock equivalents are comprised of stock options, restricted stock units and convertible preferred stock outstanding. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted net loss per share.Potentially dilutive securities not included in the calculation of diluted net loss per common share, because to do so would be anti-dilutive, were (in common stock equivalent shares) 131,659,415 for the three months ended March 31, 2022 and 89,859,197 for the three months ended March 31, 2021, and consisted of convertible preferred stock, warrants, stock options and restricted stock units.

Investments

Investments	3 Months Ended
	Mar. 31, 2022
Debt Securities, Available-for-sale [Abstract]
Investments	InvestmentsHistorically, we have invested our excess cash primarily in debt instruments of financial institutions, corporations, U.S. government-sponsored agencies and the U.S. Treasury. We generally hold our investments to maturity and do not sell our investments before we have recovered our amortized cost basis. As of March 31, 2022 and December 31, 2021, our cash balance was comprised entirely of cash and cash equivalents (money market funds) and there was no unrealized gain or loss in either period.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We have certain financial assets recorded at fair value which have been classified as Level 1, 2, or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements. Accounting standards define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants as of the measurement date. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The accounting standards provide an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that market participants would use in valuing the asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect our assumptions about the factors that market participants would use in valuing the asset or liability. The accounting standards prioritize the inputs used in measuring the fair value into the following hierarchy: • Level 1 includes financial instruments for which quoted market prices for identical instruments are available in active markets. • Level 2 includes financial instruments for which there are inputs other than quoted prices included within Level 1 that are observable for the instrument such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets with insufficient volume or infrequent transactions (less active markets) or model-driven valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data. • Level 3 includes financial instruments for which fair value is derived from valuation techniques in which one or more significant inputs are unobservable, including management’s own assumptions. Financial Assets Measured at Fair Value The following table presents our fair value hierarchy for assets measured at fair value on a recurring basis as of March 31, 2022 and December 31, 2021 (in thousands): Fair value as of March 31, 2022 Total Level 1 Level 2 Level 3 Assets: Cash equivalents (money market funds) $ 49,911 $ 49,911 $ — $ — $ 49,911 $ 49,911 $ — $ — Fair value as of December 31, 2021 Total Level 1 Level 2 Level 3 Assets: Cash equivalents (money market funds) $ 57,905 $ 57,905 $ — $ — $ 57,905 $ 57,905 $ — $ —

Debt

Debt	3 Months Ended
	Mar. 31, 2022
Debt Disclosure [Abstract]
Debt	Debt Term Loan On June 17, 2016, we entered into a loan and security agreement ("Loan Agreement") with Oxford Finance, LLC, (the “ Lender ” ), pursuant to which we received $20.0 million in proceeds, net of debt issuance costs, on June 22, 2016 (the "Term Loan"). The outstanding Term Loan will mature on May 1, 2024 (the “Maturity Date”) and bears interest at a floating per annum rate equal to (i) 8.51% plus (ii) the greater of (a) the 30 day U.S. Dollar LIBOR rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue and (b) 0.44%. Under the original Loan Agreement, we were required to make interest-only payments through June 1, 2018, followed by 24 equal monthly payments of principal and unpaid accrued interest. The Loan Agreement was amended nine times between October 2017 through May 2020. On A ugust 25, 2020 we entered into a tenth amendment to the Loan Agreement with the Lender (the "Tenth Amendment"). Pursuant to the terms of the Tenth Amendment, we were eligible for up to an additional seven months of interest only payments in the event we paid down $10.0 million in loan principal before April 30, 2021 (the "Principal Paydown Event"). We prepaid $1.0 million, $4.0 million and $5.0 million of outstanding principal to the Lender on September 30, 2020, October 8, 2020 and November 30, 2020, respectively, for a total of $10.0 million. We also paid the applicable 5.5% final payment fees related to the three prepayments to the Lender. As the Principal Paydown Event occurred by April 30, 2021, we received an additional seven months of interest only payment extension and were not obligated to make principal payments on the Term Loan until January 1, 2022. On December 31, 2021, we entered into an eleventh amendment to the Loan Agreement (the "Eleventh Amendment"). Under the terms of the Eleventh Amendment, our required monthly payments to the Lender are to be comprised of interest only through and including (i) December 1, 2022, if the 2022 Equity Event (as defined below) does not occur or (ii) December 1, 2023 if the 2022 Equity Event occurs. The “2022 Equity Event” means the receipt by us, during the calendar year 2022, of unrestricted net cash proceeds of at least $20.0 million from the sale and issuance of our equity securities. In addition, the maturity date for the Term Loan was extended to May 1, 2024. If the 2022 Equity Event does not occur, then commencing on January 1, 2023 and continuing on each successive payment date thereafter through and including the maturity date of May 1, 2024, we will be required to make consecutive equal monthly payments of principal, together with applicable interest, in arrears, to the Lender. If the 2022 Equity Event does occur, then commencing on January 1, 2024 and continuing on each successive payment date thereafter through and including the maturity date of May 1, 2024, we will be required to make consecutive equal monthly payments of principal, together with applicable interest, in arrears, to the Lender. The Eleventh Amendment also provides that we are required to maintain a minimum cash balance of $5.0 million. As consideration for the Lender’s entry into the Eleventh Amendment, we made a payment of $0.3 million to the Lender. We used the proceeds from the Term Loan solely for working capital and to fund our general business requirements. Our obligations under the Loan Agreement are secured by a first priority security interest in substantially all of our current and future assets, other than our intellectual property, for which the Lender currently has a positive lien. We have also agreed not to encumber our intellectual property assets, except as permitted by the Loan Agreement. The Loan Agreement includes customary events of default, including instances of a material adverse change in our operations, that may require prepayment of the outstanding Term Loan. We are in compliance with all Loan Agreement covenants as of the date of the filing of this Form 10-Q. As of March 31, 2022, $4.7 million of principal was outstanding under the Term Loan. An additional $1.3 million is also payable at the conclusion of the Term Loan (the related $1.2 million accrued liability balance is presented in other long-term liabilities on our balance sheet at March 31, 2022). We had less than $0.1 million of debt issuance costs outstanding as of March 31, 2022, which are being accreted to interest expense over the life of the Term Loan using an effective interest rate of 8.98%. The exit fees are being accrued over the life of the Term Loan through interest expense. As of March 31, 2022, future principal payments for the Term Loan due under the Loan Agreement are as follows (in thousands): 2022 $ — 2023 3,304 2024 1,377 $ 4,681 Paycheck Protection Program Loan

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock As of March 31, 2022, there were 145,981,180 shares of common stock outstanding. Each share of common stock is entitled to one vote. The holders of the common stock are also entitled to receive dividends whenever funds are legally available and when declared by our Board of Directors. 2019 Equity Incentive Plan On June 15, 2019, the Company's board of directors approved, and on August 1, 2019 the Company's stockholders approved, the Company's 2019 Equity Incentive Plan (the "2019 Plan"). The 2019 Plan is the successor to and continuation of the Company's 2012 Equity Incentive Plan . The number of shares authorized for issuance under the 2019 Plan may be increased by (a) the shares subject to outstanding stock awards granted under the Company’s 2009 Equity Incentive Plan (the “2009 Plan”) and the Company’s 2012 Equity Incentive Plan (together the with 2009 Plan, the “Prior Plans”) that on or after the effective date of the 2019 Plan (i) expire or terminate for any reason prior to exercise or settlement; (ii) are forfeited because of the failure to meet a contingency or condition required to vest such shares or otherwise return to the Company, or (iii) are reacquired, withheld (or not issued) to satisfy a tax withholding obligation in connection with an award or to satisfy the purchase price or exercise price of a stock award. No further grants will be made under the Prior Plan s. In addition, on January 22, 2020, an additional 4,166,860 shares of common stock became available for issuance under the 2019 Plan pu rsuant to the Milestone Closing (defined below) of the May 2019 SPA (defined below). Further, on January 1 st of each year, for a period of not more than ten years, beginning on January 1, 2021 and continuing through January 1, 2029, the number of shares authorized for issuance under the 2019 Plan will increase by 5.0% of the total number of shares of our capital stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by our Board of Directo rs. As of March 31, 2022, 4,452,863 shares of common stock were available for new equity award grants under the 2019 Plan and 13,871,693 shares of common stock were reserved for issuance pursuant to equity awards outstanding under the 2019 Plan as of March 31, 2022. 2021 Inducement Plan On November 23, 2021, our Board of Directors adopted the 2021 Inducement Plan (the “Inducement Plan”), which became effective immediately. Stockholder approval of the Inducement Plan was not required pursuant to Rule 5635(c)(4) of the Nasdaq Listing Rules. The Inducement Plan initially reserved 2,000,000 shares of common stock and provides for the grant of NSOs that was used exclusively for grants to individuals that were not previously employees or directors of the Company, as an inducement material to the individual’s entry into employment with the Company. Under the Inducement Plan, options were granted with varying vesting terms, but typically vested over four years, with 25% of the total grant vesting on the first anniversary of the effective date of the option grant and the remaining grant vesting monthly thereafter over the following 36 months. As of March 31, 2022, 1,800,000 shares of common stock were reserved for future issuance under the Inducement Plan and 200,000 shares of common stock were reserved for future issuance pursuant to equity awards outstanding under the Inducement Plan. Private Placements of Common Stock, Non-Voting Preferred Stock and Warrants On May 3, 2019, we entered into a securities purchase agreement (the "May 2019 SPA") with certain institutional and other accredited investors, including certain directors, executive officers and employees of the Company (the “Purchasers”), pursuant to which we agreed to sell and issue shares of our common stock, shares of our newly designated non-voting convertible preferred stock, and warrants to purchase common stock, in up to two closings, in a private placement transaction (the “Private Placement”). At an initial closing under the May 2019 SPA that occurred on May 7, 2019 (the “Initial Closing”), we sold and issued to the Purchasers (i) 9,730,534 shares of common stock and accompanying warrants to purchase up to an aggregate of 9,730,534 shares of common stock at a combined purchase price of $1.205 per share, and (ii) 415,898 shares of non-voting Class A-1 convertible preferred stock, in lieu of shares of common stock, at a price of $10.80 per share, and accompanying warrants to purchase an aggregate of 4,158,980 shares of common stock at a price of $0.125 for each share of common stock underlying such warrants. Total gross proceeds from the Initial Closing were approximately $16.7 million, which does not include any proceeds that may be received upon exercise of the warrants. Each share of non-voting Class A-1 convertible preferred stock is convertible into 10 shares of Common Stock, subject to certain beneficial ownership conversion limitations. The warrants are exercisable for a period of five years following the date of issuance and have an exercise price of $1.08 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events. The warrants are exercisable on a net exercise "cashless" basis. An aggregate of 526,083 shares of common stock and warrants to purchase up to 526,083 shares of common stock were purchased for $0.6 million by certain directors and executive officers of the Company under the Initial Closing. At a second closing under the May 2019 SPA that occurred on December 24, 2019 (the “Milestone Closing”), we sold and issued to the Purchasers 3,288,390 shares of non-voting Class A-2 convertible preferred stock and accompanying warrants to purchase an aggregate of 32,883,900 shares of common stock for an aggregate purchase price of approximately $26.0 million. Net proceeds to the Company from the Milestone Closing were approximately $24.6 million. Each share of non-voting Class A-2 convertible preferred stock is convertible into 10 shares of Common Stock, subject to certain beneficial ownership conversion limitations. The warrants will be exercisable for a period of five years following the date of issuance and have an exercise price of $0.666 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events. The warrants may be exercised on a net exercise “cashless” basis. An aggregate of 121,581 shares of Class A-2 convertible preferred stock and warrants to purchase up to 1,215,810 shares of common stock were purchased for approximately $1.0 million by certain directors and executive officers of the Company under the Milestone Closing. We evaluated the non-voting Class A-1 convertible preferred stock and common stock warrants sold in the Initial Closing and the Class A-2 convertible preferred stock and common stock warrants sold in the Milestone Closing under ASC 480, Distinguishing Liabilities from Equity, and ASC 815, Derivatives and Hedging, and determined permanent equity treatment was appropriate for these freestanding financial instruments. The Initial Closing and Milestone Closing did not include any embedded features that required bifurcation. The non-voting Class A-2 convertible preferred stock and warrants issuable under the Milestone Closing were not subject to accounting recognition until the Milestone Closing occurred, as the terms of the Milestone Closing did not provide a right or an obligation on either the Company nor the Purchasers. On December 1, 2020, we entered into a Securities Purchase Agreement (the "December 2020 SPA") with certain institutional and other accredited investors, including certain directors, executive officers and employees of the Company (the “2020 Purchasers”), pursuant to which we agreed to sell and issue shares of our common stock, shares of newly designated non-voting convertible preferred stock and warrants to purchase common stock (the “2020 PIPE”). At the closing under the December 2020 SPA that occurred on December 4, 2020 (the “2020 Closing”), we sold and issued to the 2020 Purchasers (i) 24,341,607 shares of common stock and accompanying warrants to purchase up to an aggregate of 18,256,204 shares of common stock at a combined purchase price of $0.7464 per share, and (ii) 272,970 shares of non-voting Class A-3 convertible preferred stock, in lieu of shares of common stock, at a price of $6.22 per share, and accompanying warrants to purchase an aggregate of 2,047,276 shares of common stock at a price of $0.125 for each share of common stock underlying such warrants. Total gross proceeds from the 2020 Closing were approximately $19.4 million, which does not include any proceeds that may be received upon exercise of the warrants. Each share of non-voting Class A-3 convertible preferred stock is convertible into 10 shares of common stock, subject to certain beneficial ownership conversion limitations. The warrants are exercisable for a period of five years following the date of issuance and have an exercise price of $0.7464 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events. The warrants are exercisable on a net exercise "cashless" basis. An aggregate of 833,208 shares of common stock and warrants to purchase up to 624,906 shares of common stock were purchased for $0.6 million by certain directors and executive officers of the Company at the 2020 Closing. We evaluated the non-voting Class A-3 convertible preferred stock and common stock warrants sold in the 2020 PIPE under ASC 480, Distinguishing Liabilities from Equity, and ASC 815, Derivatives and Hedging, and determined permanent equity treatment was appropriate for these freestanding financial instruments and there were no embedded features that required bifurcation. On November 24, 2021, we entered into a Securities Purchase Agreement (the "November 2021 SPA") with certain institutional and other accredited investors, including one of the Company's directors (the “2021 Purchasers”), p ursuant to which we agreed to sell and issue shares of our common stock and shares of newly designated non-voting convertible preferred stock (the “2021 PIPE”). At the closing under the November 2021 SPA that occurred on November 30, 2021 (the “2021 Closing”), we sold and issued to the 2021 Purchasers (i) 58,923,352 shares of common stock at a purchase price of $0.36 per share, and (ii) 3,725,720 shares of non-voting Class A-4 convertible preferred stock, in lieu of shares of common stock, at a price of $3.60 per share. Total gross proceeds from the 2021 Closing were approximately $34.6 million. Each share of non-voting Class A-4 convertible preferred stock is convertible into 10 shares of common stock, subject to certain beneficial ownership conversion limitations. An aggregate of 2,222,222 shares of common stock were purchased for $0.8 million by a director of the Company at the 2021 Closing. We evaluated the non-voting Class A-4 convertible preferred stock sold in the 2021 PIPE under ASC 480, Distinguishing Liabilities from Equity, and ASC 815, Derivatives and Hedging, and determined permanent equity treatment was appropriate for these freestanding financial instruments and there were no embedded features that required bifurcation. The following table summarizes preferred stock conversions and warrant exercises (and the related impact on common stoc k) under the May 2019 SPA, the December 2020 SPA and the November 2021 SPA for the three months ended March 31, 2022 and 2021 ( in thousands): Class A-1 Convertible Preferred Stock Class A-2 Convertible Preferred Stock Class A-3 Convertible Preferred Stock Class A-4 Convertible Preferred Stock Warrants Common Stock Balance at December 31, 2021 257 1,331 259 3,726 61,868 Conversions/Exercises — — — — — Balance at March 31, 2022 257 1,331 259 3,726 61,868 Balance at December 31, 2020 257 1,416 259 — 66,038 Conversions/Exercises — (78) — — (3,920) 3,199 Balance at March 31, 2021 257 1,338 259 — 62,118 ATM Offering On December 12, 2018, we entered into a Common Stock Sales Agreement (the “Stock Sales Agreement”) with H.C. Wainwright & Co., LLC (“HCW”), pursuant to which we may sell and issue shares of our common stock from time to time through HCW, as our sales agent (the “ATM Offering”). We have no obligation to sell any shares of common stock in the ATM Offering, and may at any time suspend offers under the Stock Sales Agreement or terminate the Stock Sales Agreement. Subject to the terms and conditions of the Stock Sales Agreement, HCW will use its commercially reasonable efforts to sell shares of our common stock from time to time based upon our instructions (including any price, time or size limits or other parameters or conditions that we may impose, subject to certain restrictions). We pay HCW a commission of 3.0% of the gross sales price of any shares sold under the Stock Sales Agreement. No shares were sold under the ATM Offering during the three months ended March 31, 2022. A total of 4,009,585 shares were sold and settled for proceeds of $5.8 million (net of $0.2 million in offering costs) under the Stock Sales Agreement during the three months ended March 31, 2021. On August 10, 2021, we increased the amount of common stock available for sale in the ATM Offering under the Stock Sales Agreement to $50.0 million. At March 31, 2022, approximately $50.0 million remained eligible to be sold in the ATM Offering, subject to compliance with the rules applicable to sales on Form S-3. Shares Reserved for Future Issuance The following shares of common stock were reserved for future issuance as of March 31, 2022 (in thousands): Class A-1 convertible preferred stock outstanding (as-converted) 2,567 Class A-2 convertible preferred stock outstanding (as-converted) 13,308 Class A-3 convertible preferred stock outstanding (as-converted) 2,587 Class A-4 convertible preferred stock outstanding (as-converted) 37,257 2019 PIPE Initial Closing warrants 12,778 2019 PIPE Milestone Closing warrants 30,595 2020 PIPE warrants 18,495 Common stock options outstanding 12,846 RSUs outstanding 1,226 Common stock available for future grant under the 2019 Equity Incentive Plan 4,453 Common stock available for future grant under the 2021 Inducement Plan 1,800 Employee Stock Purchase Plan 291 Total common shares reserved for future issuance 138,203 The following table summarizes our stock option and RSU (together Stock Awards) activity under all equity incentive plans for the three months ended March 31, 2022 (shares in thousands): Number of Weighted Number of Weighted average grant date fair value Stock Awards outstanding at December 31, 2021 8,661 $ 1.17 401 $ 0.95 Granted 4,357 $ 0.26 848 $ 0.26 Canceled/forfeited/expired (172) $ 0.90 (23) $ 0.95 Stock Awards outstanding at March 31, 2022 12,846 $ 0.87 1,226 $ 0.47 Stock-Based Compensation The following table summarizes the weighted average assumptions used to estimate the fair value of stock options and performance stock awards granted to employees under our 2012 Equity Incentive Plan, 2015 Inducement Plan, 2019 Equity Incentive Plan, 2021 Inducement Plan and the shares purchasable under our Employee Stock Purchase Plan during the periods presented: Three months ended 2022 2021 Stock options Risk-free interest rate 1.7 % 0.9 % Volatility 95.7 % 95.7 % Dividend yield — — Expected term (years) 6.1 6.1 Performance stock options Risk-free interest rate — 1.0 % Volatility — 95.7 % Dividend yield — — Expected term (years) 0.0 6.1 Employee stock purchase plan shares Risk-free interest rate 0.3 % 0.1 % Volatility 97.8 % 101.3 % Dividend yield — — Expected term (years) 0.5 0.5 The following table summarizes the allocation of our stock-based compensation expense for all stock awards during the periods presented (in thousands): Three months ended 2022 2021 Research and development $ 270 $ 181 General and administrative 730 510 Total $ 1,000 $ 691

Collaborations

Collaborations	3 Months Ended
	Mar. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations	Collaborations Revenue recognized from our strategic collaborations was zero for the three months ended March 31, 2022 and 2021. Sanofi In July 2012, we amended and restated our collaboration and license agreement with Sanofi to expand the potential therapeutic applications of the micro RNA alliance targets to be developed under such agreement. The following elements were delivered as part of the strategic collaboration with Sanofi: (1) a license for up to four micro RNA targets; and (2) a research license under our technology collaboration. In June 2013, the original research term expired, upon which we and Sanofi entered into an option agreement pursuant to which Sanofi was granted an exclusive right to negotiate the co-development and commercialization of certain of our unencumbered micro RNA programs and we were granted the exclusive right to negotiate with Sanofi for co-development and commercialization of certain miR-21 anti-miRs in oncology and Alport syndrome. In February 2014, we and Sanofi entered into a second amended and restated collaboration and license agreement (the “2014 Sanofi Amendment”) to discover, develop and commercialize micro RNA therapeutics to focus on specific orphan disease and oncology targets. Under the terms of the 2014 Sanofi Amendment, Sanofi had opt-in rights to our clinical fibrosis program targeting miR-21 for the treatment of Alport syndrome, our preclinical program targeting miR-21 for oncology indications, and our preclinical program targeting miR-221/222 for hepatocellular carcinoma (“HCC”). We were responsible for developing each of these programs to proof-of-concept, at which time Sanofi had an exclusive option on each program. If Sanofi chooses to exercise its option on any of these programs, Sanofi would reimburse us for a significant portion of our preclinical and clinical development costs and would also pay us an option exercise fee for any such program, provided that $1.25 million of the $2.5 million upfront option fee paid to us by Sanofi in connection with the June 2013 option agreement will be creditable against such option exercise fee. We are eligible to receive royalties on micro RNA therapeutic products commercialized by Sanofi and will have the right to co-promote these products relating to our preclinical program targeting miR-221/222. As indicated below, we entered into an additional amendment with Sanofi in November 2018, under which Sanofi's opt-in rights to our miR-21 programs under the 2014 Sanofi Amendment were relinquished. Sanofi's opt-in rights with regard to our miR-221/222 preclinical program under the 2014 Sanofi Amendment remained unchanged. We are eligible to receive milestone payments related to the development and commercialization of miR-221/222 for HCC of up to $38.8 million for proof-of-concept option exercise fees (net of $1.25 million creditable, as noted above), $25.0 million for clinical milestones and up to $130.0 million for regulatory and commercial milestones. In addition, we are entitled to receive royalties based on a percentage of net sales of any products from the miR-221/222 program which, in the case of sales in the United States, will be in the middle of the 10% to 20% range, and, in the case of sales outside of the United States, will range from the low end to the middle of the 10% to 20% range, depending upon the volume of sales. If we exercise our option to co-promote a miR-221/222 product, we will continue to be eligible to receive royalties on net sales of each product in the United States at the same rate, unless we elect to share a portion of Sanofi’s profits from sales of such product in the United States in lieu of royalties. In November 2018, we entered into an amendment to the 2014 Sanofi Amendment with Sanofi to modify the parties’ rights and obligations with respect to our miR-21 programs, including our RG-012 program (the “2018 Sanofi Amendment”). Under the terms of the 2018 Sanofi Amendment, we have granted Sanofi a worldwide, royalty-free, fee-bearing, exclusive license, with the right to grant sublicenses, under our know-how and patents to develop and commercialize miR-21 compounds and products for all indications, including Alport Syndrome. Sanofi will control and will assume all responsibilities and obligations for developing and commercializing each of our miR-21 programs, including our obligations regarding the administration and expense of clinical trials and all other costs, including in-license royalties and other in-license payments, related to our miR-21 programs. Under the terms of the 2018 Sanofi Amendment, we have assigned to Sanofi certain agreements, product-specific patents and all materials directed to miR-21 or to any miR-21 compound or product and are required to provide reasonable technical assistance to Sanofi for a period of 24 months after the date of the 2018 Sanofi Amendment. Under the terms of the 2018 Sanofi Amendment, we were eligible to receive approximately $6.8 million in upfront payments for the license and for miR-21 program-related materials (collectively, the “Upfront Amendment Payments”). We were also eligible to receive up to $40.0 million in development milestone payments, including a $10.0 million payment for an interim enrollment milestone (the "Enrollment Milestone"). In addition, Sanofi has agreed to reimburse us for certain out-of-pocket transition activities and assume our upstream license royalty obligations. In 2019, we completed the performance obligations under the 2018 Sanofi Amendment and recognized revenue for the $6.8 million in Upfront Amendment Payments. In August 2020, we entered into an amendment to the 2018 Sanofi Amendment (the "2020 Sanofi Amendment"). Under the terms of the 2020 Sanofi Amendment, we agreed to transfer to Sanofi additional RG-012 development program materials (the “Materials”) in exchange for a payment from Sanofi of $1.0 million (the “Transfer Payment”). In addition, in lieu of the $10.0 million Enrollment Milestone under the 2018 Sanofi Amendment, Sanofi agreed to pay us a $4.0 million milestone upon the completion of the transfer and verification of the Materials, and $5.0 million upon achievement of the Enrollment Milestone. Additionally, we are eligible to receive $25.0 million upon achievement of an additional development milestone related to Sanofi's development of the miR-21 compounds. In September 2020, we received $1.0 million in exchange for the transfer of the Materials to Sanofi, and received an additional $4.0 million in October 2020 as a result of Sanofi's completion and verification of the Materials in September 2020. As the performance obligations associated with both of these payments had been satisfied under Topic 606 as of September 30, 2020, both amounts were recognized as revenue in the third quarter of 2020. In November 2020, we received $5.0 million upon achievement of the Enrollment Milestone. As the performance obligations associated with this payment had been satisfied under Topic 606 as of December 31, 2020, this amount was recognized as revenue in the fourth quarter of 2020. As of March 31, 2022, th e $25.0 million in development milestone payments (variable consideration) is fully constrained and therefore, does not meet the criteria for revenue recognition.

Leases

Leases	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Leases	Leases At the inception of a contractual arrangement, we determine whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. For operating leases with an initial term greater than 12 months, we recognize operating lease right of use assets ("ROU assets") and operating lease liabilities based on the present value of lease payments over the lease term at the commencement date. Operating lease ROU assets are comprised of the lease liability plus any lease payments made and excludes lease incentives. Lease terms include options to renew or terminate the lease when we are reasonably certain that the renewal option will be exercised or when it is reasonably certain that the termination option will not be exercised. For our operating leases, we generally cannot determine the interest rate implicit in the lease, in which case we use our incremental borrowing rate as the discount rate for the lease. We estimate our incremental borrowing rate for our operating leases based on what we would normally pay to borrow on a collateralized basis over a similar term for an amount equal to the lease payments. Operating lease expense is recognized on a straight-line basis over the lease term. Leases with a lease term of 12 months or less at inception are not recorded on the unaudited condensed balance sheet. Instead, we recognize lease expense for these leases on a straight-line basis over the lease term. Our lease agreements do not contain any material variable lease payments, residual value guarantees or restrictive covenants. Certain leases require us to pay taxes, insurance, utilities, and maintenance costs for the building, which do not represent lease components. We elected to not separate lease and non-lease components. On June 19, 2019, we entered into a lease agreement (the “Prior Lease”) with ARE SD Region No.44 LLC ("Landlord") for the lease of approximately 8,727 square feet of rentable area of the building located at 10628 Science Center Drive, Suite 225, San Diego, California 92121 (the “Prior Premises”). The commencement date of the Prior Lease was July 1, 2019 (the “Prior Commencement Date”). We used the Prior Premises as our principal executive offices and as a laboratory for research and development and other related uses. The term of the Prior Lease (the “Prior Initial Term”) was two years, six months, ending December 31, 2021. The base rent payments due for the Prior Premises were $0.4 million in 2020 and $0.4 million in 2021, net of certain rent abatement terms. We were also responsible for the payment of additional rent to cover our share of the annual operating expenses of the building, the annual tax expenses of the building and the annual utilities cost of the building. On July 1, 2019, we recorded a $0.8 million lease liability for the Prior Lease, which was calculated as the present value of future lease payments to be made under the Prior Lease. A $0.6 million ROU asset was also recorded on July 1, 2019, which represents the difference between the lease liability and the remaining $0.2 million deferred credit for the reduction of the lease liability under the operating lease agreement with Landlord dated February 25, 2019. On February 11, 2021, we entered into a lease agreement (the "Campus Point Lease") with ARE-SD Region No. 61, LLC (as successor in interest to ARE-SD Region No. 58, LLC) ("Campus Point Landlord"), for the lease of approximately 13,438 square feet of rentable area located at 4224 Campus Point Court, Suite 210, San Diego, California, 92121 (the "Campus Point Premises"). The commencement date of the Campus Point Lease was April 15, 2021. However, for accounting purposes the lease commencement date was February 11, 2021. We are using the Campus Point Premises as our new principal executive offices and as a laboratory for research and development. The term of the Campus Point Lease (“Campus Point Initial Term”) is 60 months, ending April 30, 2026. The aggregate base rent due over the initial term of the Campus Point Lease is approximately $3.8 million. We are also responsible for the payment of additional amounts to cover our share of the annual operating expenses of the building, the annual tax expenses of the building and the utilities costs for the building. On February 11, 2021, concurrently with entry into the Campus Point Lease, we entered into an Assignment and Assumption of Lease (the “Assignment Agreement”) with Turning Point Therapeutics, Inc. (“Assignee”) and a Consent to Assignment (the "Consent") with Landlord. Pursuant to the Assignment Agreement, we assigned all rights, title, and interest under the Prior Lease to Assignee and delivered the Prior Premises to Assignee on April 22, 2021. Pursuant to the Assignment Agreement, Assignee paid us $60,000 in non-refundable assignment consideration. Additionally, the Consent stipulates that we were not required to pay a fee pursuant to the Prior Lease in connection with the assignment. The execution of the Campus Point Lease, Consent, and Assignment Agreement resulted in a modification which was not accounted for as a separate contract. Rather, we accounted for the three contracts with Campus Point Landlord in combination, as they were entered into at the same time and negotiated as a package to achieve the same commercial objective. We accounted for a $0.2 million reduction in the lease liability for the Prior Lease as a deferred credit that is amortized as a reduction to rent expense over the term of the Campus Point Lease. A lease liability of less than $0.1 million and ROU asset of less than $0.1 million remained with respect to the Prior Lease and was fully amortized as of April 30, 2021. On February 11, 2021, we recorded a $3.2 million lease liability for the Campus Point Lease, which was calculated as the present value of future lease payments to be made under the Campus Point Lease. A $3.0 million ROU asset was also recorded on February 11, 2021, which represents the difference between the lease liability and the $0.2 million deferred credit for the reduction of the lease liability under the Prior Lease. Our future lease payments under operating leases at March 31, 2022 are as follows (in thousands): Operating Leases Remaining 2022 $ 569 2023 776 2024 800 2025 824 2026 277 Total operating lease payments $ 3,246 Less: amount representing interest (380) Present value of obligations under operating leases 2,866 Less: current portion (604) Long-term operating lease obligations $ 2,262

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and 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. In management’s opinion, the accompanying financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented. Interim financial results are not necessarily indicative of results anticipated for the full year. These unaudited condensed financial statements should be read in conjunction with the audited financial statements and footnotes included in our Annual Report on Form 10-K for the year ended December 31, 2021, from which the balance sheet information herein was derived.
Use of Estimates	Use of Estimates Our condensed financial statements are prepared in accordance with GAAP, which requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in our financial statements and accompanying notes. An estimated loss contingency is accrued in our financial statements if it is probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Although these estimates are based on our knowledge of current events and actions we may undertake in the future, actual results may ultimately differ from these estimates and assumptions. Additionally, the impact of the COVID-19 pandemic to our business and operating results presents additional uncertainty.
Stock-Based Compensation	Stock-Based Compensation We account for stock-based compensation expense related to stock options granted to employees and members of our board of directors by estimating the fair value of each stock option on the date of grant using the Black-Scholes option pricing model. We recognize stock-based compensation expense using the accelerated multiple-option approach. Under the accelerated multiple-option approach (also known as the graded-vesting method), we recognize compensation expense over the requisite service period for each separately vesting tranche of the award as though the award was in substance multiple awards, resulting in accelerated expense recognition over the vesting period. For performance-based awards granted to employees (i) the fair value of the award is determined on the grant date, (ii) we assess the probability of the individual milestones under the award being achieved and (iii) the fair value of the shares subject to the milestone is expensed over the implicit service period commencing once management believes the performance criteria is probable of being met. We account for restricted stock units by determining the fair value of each restricted stock unit based on the closing market price of our common stock on the date of grant. We recognize stock-based compensation expense using the accelerated multiple-option approach over the requisite service periods of the awards, and forfeitures are recognized as they occur.
Clinical Trial and Preclinical Study Accruals	Clinical Trial and Preclinical Study AccrualsWe make estimates of our accrued expenses for clinical trial and preclinical study activities as of each balance sheet date in our financial statements based on the facts and circumstances known to us at that time. These accruals are based upon estimates of costs incurred and fees that may be associated with services provided by clinical trial investigational sites and CROs and for other clinical trial-related activities. Payments under certain contracts with such parties depend on factors such as successful enrollment of patients, site initiation and the completion of clinical trial milestones. In accruing for these services, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If possible, we obtain information regarding unbilled services directly from these service providers. However, we may be required to estimate these services based on other information available to us. If we underestimate or overestimate the activities or fees associated with a study or service at a given point in time, adjustments to research and development expenses may be necessary in future periods. Historically, our estimated accrued liabilities have approximated actual expense incurred. Subsequent changes in estimates may result in a material change in our accruals.
Prepaid Materials	Prepaid Materials We capitalize the purchase of certain raw materials and related supplies for use in the manufacturing of drug product in our preclinical and clinical development programs, as we have determined that these materials have alternative future use. We can use these raw materials and related supplies in multiple clinical drug products, and therefore these raw materials have future use independent of the development status of any particular drug program until it is utilized in the manufacturing process. We expense the cost of materials when used. We periodically review these capitalized materials for continued alternative future use and write down the asset to its net realizable value in the period in which an impairment is identified.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . Subsequently, in November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments-Credit Losses . ASU 2016-13 requires entities to measure all expected credit losses for most financial assets held at the reporting date based on an expected loss model which includes historical experience, current conditions, an d reasonable and supportable forecasts. ASU 2016-13 also requires enhanced disclosures to help financial statement users better understand significant estimates and judgments used in estimating credit losses. This ASU is effective for smaller reporting companies for fiscal years beginning after December 15, 2022, with early adoption permitted. We are assessing the impact this standard will have on our financial statements and disclosures. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848),
Fair Value Measurement	Fair Value Measurements We have certain financial assets recorded at fair value which have been classified as Level 1, 2, or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements. Accounting standards define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants as of the measurement date. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The accounting standards provide an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that market participants would use in valuing the asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs that reflect our assumptions about the factors that market participants would use in valuing the asset or liability. The accounting standards prioritize the inputs used in measuring the fair value into the following hierarchy: • Level 1 includes financial instruments for which quoted market prices for identical instruments are available in active markets. • Level 2 includes financial instruments for which there are inputs other than quoted prices included within Level 1 that are observable for the instrument such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets with insufficient volume or infrequent transactions (less active markets) or model-driven valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data. • Level 3 includes financial instruments for which fair value is derived from valuation techniques in which one or more significant inputs are unobservable, including management’s own assumptions.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents our fair value hierarchy for assets measured at fair value on a recurring basis as of March 31, 2022 and December 31, 2021 (in thousands): Fair value as of March 31, 2022 Total Level 1 Level 2 Level 3 Assets: Cash equivalents (money market funds) $ 49,911 $ 49,911 $ — $ — $ 49,911 $ 49,911 $ — $ — Fair value as of December 31, 2021 Total Level 1 Level 2 Level 3 Assets: Cash equivalents (money market funds) $ 57,905 $ 57,905 $ — $ — $ 57,905 $ 57,905 $ — $ —

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2022
Debt Disclosure [Abstract]
Debt Maturities	As of March 31, 2022, future principal payments for the Term Loan due under the Loan Agreement are as follows (in thousands): 2022 $ — 2023 3,304 2024 1,377 $ 4,681

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Activity of Shares	The following table summarizes preferred stock conversions and warrant exercises (and the related impact on common stoc k) under the May 2019 SPA, the December 2020 SPA and the November 2021 SPA for the three months ended March 31, 2022 and 2021 ( in thousands): Class A-1 Convertible Preferred Stock Class A-2 Convertible Preferred Stock Class A-3 Convertible Preferred Stock Class A-4 Convertible Preferred Stock Warrants Common Stock Balance at December 31, 2021 257 1,331 259 3,726 61,868 Conversions/Exercises — — — — — Balance at March 31, 2022 257 1,331 259 3,726 61,868 Balance at December 31, 2020 257 1,416 259 — 66,038 Conversions/Exercises — (78) — — (3,920) 3,199 Balance at March 31, 2021 257 1,338 259 — 62,118
Common Stock Reserved for Future Issuance	The following shares of common stock were reserved for future issuance as of March 31, 2022 (in thousands): Class A-1 convertible preferred stock outstanding (as-converted) 2,567 Class A-2 convertible preferred stock outstanding (as-converted) 13,308 Class A-3 convertible preferred stock outstanding (as-converted) 2,587 Class A-4 convertible preferred stock outstanding (as-converted) 37,257 2019 PIPE Initial Closing warrants 12,778 2019 PIPE Milestone Closing warrants 30,595 2020 PIPE warrants 18,495 Common stock options outstanding 12,846 RSUs outstanding 1,226 Common stock available for future grant under the 2019 Equity Incentive Plan 4,453 Common stock available for future grant under the 2021 Inducement Plan 1,800 Employee Stock Purchase Plan 291 Total common shares reserved for future issuance 138,203
Stock Option Activity	The following table summarizes our stock option and RSU (together Stock Awards) activity under all equity incentive plans for the three months ended March 31, 2022 (shares in thousands): Number of Weighted Number of Weighted average grant date fair value Stock Awards outstanding at December 31, 2021 8,661 $ 1.17 401 $ 0.95 Granted 4,357 $ 0.26 848 $ 0.26 Canceled/forfeited/expired (172) $ 0.90 (23) $ 0.95 Stock Awards outstanding at March 31, 2022 12,846 $ 0.87 1,226 $ 0.47
Assumptions Used to Estimate Fair Value of Stock Options and Performance Stock and Employee Stock Purchase Plan	The following table summarizes the weighted average assumptions used to estimate the fair value of stock options and performance stock awards granted to employees under our 2012 Equity Incentive Plan, 2015 Inducement Plan, 2019 Equity Incentive Plan, 2021 Inducement Plan and the shares purchasable under our Employee Stock Purchase Plan during the periods presented: Three months ended 2022 2021 Stock options Risk-free interest rate 1.7 % 0.9 % Volatility 95.7 % 95.7 % Dividend yield — — Expected term (years) 6.1 6.1 Performance stock options Risk-free interest rate — 1.0 % Volatility — 95.7 % Dividend yield — — Expected term (years) 0.0 6.1 Employee stock purchase plan shares Risk-free interest rate 0.3 % 0.1 % Volatility 97.8 % 101.3 % Dividend yield — — Expected term (years) 0.5 0.5
Stock-Based Compensation	The following table summarizes the allocation of our stock-based compensation expense for all stock awards during the periods presented (in thousands): Three months ended 2022 2021 Research and development $ 270 $ 181 General and administrative 730 510 Total $ 1,000 $ 691

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Operating Lease, Liability, Maturity	Our future lease payments under operating leases at March 31, 2022 are as follows (in thousands): Operating Leases Remaining 2022 $ 569 2023 776 2024 800 2025 824 2026 277 Total operating lease payments $ 3,246 Less: amount representing interest (380) Present value of obligations under operating leases 2,866 Less: current portion (604) Long-term operating lease obligations $ 2,262

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Accounting Policies [Abstract]
Financing from sale proceeds, debt, and agreement revenues	$ 538,000
Cash and cash equivalents	$ 53,902	$ 60,383	$ 31,597

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Earnings Per Share [Abstract]
Potentially dilutive securities not included in calculation of diluted net loss per share (in shares)	131,659,415	89,859,197

Investments (Details)

Investments (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Abstract]
Unrealized gain (loss)	$ 0	$ 0

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Value Hierarchy for Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	$ 49,911	$ 57,905
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	49,911	57,905
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	0	0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	0	0
Cash equivalents (money market funds)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	49,911	57,905
Cash equivalents (money market funds) | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	49,911	57,905
Cash equivalents (money market funds) | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	0	0
Cash equivalents (money market funds) | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	$ 0	$ 0

Debt (Narrative) (Details)

Debt (Narrative) (Details)	Nov. 30, 2020USD ($)	Oct. 08, 2020USD ($)	Sep. 30, 2020USD ($)	Aug. 25, 2020USD ($)	Jun. 22, 2016USD ($)	Jun. 17, 2016payment	Mar. 31, 2022USD ($)prepayment	Dec. 31, 2022USD ($)	May 31, 2019amendment	Dec. 31, 2021USD ($)	Apr. 23, 2020USD ($)
Debt Instrument [Line Items]
Number of times agreement was amended | amendment									9
Other long-term liabilities							$ 1,193,000			$ 1,179,000
Debt Financing Agreement
Debt Instrument [Line Items]
Proceeds from borrowing under term loan					$ 20,000,000
Stated interest rate, percentage						8.51%
Number of monthly payments | payment						24
Debt fee							1,300,000
Long-term debt							4,700,000
Debt issuance costs							$ 100,000
Debt instrument effective rate							8.98%
Debt Financing Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate, percentage						0.44%
PPP Loan
Debt Instrument [Line Items]
PPP loan											$ 700,000
Tenth Amendment
Debt Instrument [Line Items]
Interest-only payment extension				7 months
Prepayment requirement				$ 10,000,000
Term Loan
Debt Instrument [Line Items]
Repayments of debt	$ 5,000,000	$ 4,000,000	$ 1,000,000				$ 10,000,000
Payment fee							5.50%
Number of prepayments to lender | prepayment							3
Additional extension for interest only payments							7 months
Other long-term liabilities							$ 1,200,000
Eleventh Amendment
Debt Instrument [Line Items]
Cash collateral for borrowed securities										5,000,000
Debt fee										$ 300,000
Eleventh Amendment | Forecast
Debt Instrument [Line Items]
Unrestricted net cash proceeds amount								$ 20,000,000

Debt (Future Principal Payments

Debt (Future Principal Payments) (Details) - Debt Financing Agreement Tranche A $ in Thousands	Mar. 31, 2022USD ($)
Debt Instrument [Line Items]
2022	$ 0
2023	3,304
2024	1,377
Long-term Debt	$ 4,681

Stockholders' Equity (Narrative

Stockholders' Equity (Narrative) (Details) $ / shares in Units, $ in Millions	Nov. 23, 2021shares	Dec. 04, 2020USD ($)$ / sharesshares	Jan. 22, 2020shares	Dec. 24, 2019USD ($)$ / sharesshares	May 07, 2019USD ($)$ / sharesshares	Nov. 30, 2021USD ($)$ / sharesshares	Mar. 31, 2022voteshares	Dec. 31, 2021shares	May 03, 2019closing
Subsidiary, Sale of Stock [Line Items]
Common stock, shares outstanding (in shares)							145,981,180	145,971,184
Common stock voting rights votes | vote							1
Total common shares reserved for future issuance (in shares)							138,203,000
Number of closings | closing									2
Private Placement
Subsidiary, Sale of Stock [Line Items]
Share sold (in shares)		24,341,607			9,730,534
Warrants callable (in shares)		18,256,204			9,730,534
Sale of stock price (in usd per share) | $ / shares		$ 0.7464			$ 1.205
Consideration received | $		$ 19.4			$ 16.7
Shares issued upon conversion (in shares)		10			10
Warrants, term					5 years
Warrant exercise price (in usd per share) | $ / shares					$ 1.08
Milestone Closing
Subsidiary, Sale of Stock [Line Items]
Consideration received | $				$ 24.6
2021 Closing
Subsidiary, Sale of Stock [Line Items]
Share sold (in shares)						58,923,352
Sale of stock price (in usd per share) | $ / shares						$ 0.36
Consideration received | $						$ 34.6
Shares issued upon conversion (in shares)						10
Preferred Class A | Private Placement
Subsidiary, Sale of Stock [Line Items]
Warrants callable (in shares)					4,158,980
Sale of stock price (in usd per share) | $ / shares					$ 10.80
Nonvoting convertible preferred stock issued (in shares)					415,898
Class A-2 Convertible Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Reverse stock split ratio				10
Class A-2 Convertible Preferred Stock | Milestone Closing
Subsidiary, Sale of Stock [Line Items]
Share sold (in shares)				3,288,390
Warrants callable (in shares)				32,883,900
Consideration received | $				$ 26
Warrants, term				5 years
Warrant exercise price (in usd per share) | $ / shares				$ 0.666
Class A-3 Convertible Preferred Stock | Private Placement
Subsidiary, Sale of Stock [Line Items]
Warrants callable (in shares)		2,047,276
Sale of stock price (in usd per share) | $ / shares		$ 6.22
Nonvoting convertible preferred stock issued (in shares)		272,970
Warrants, term		5 years
Warrant exercise price (in usd per share) | $ / shares		$ 0.7464
Class A-4 Convertible Preferred Stock | 2021 Closing
Subsidiary, Sale of Stock [Line Items]
Sale of stock price (in usd per share) | $ / shares						$ 3.60
Nonvoting convertible preferred stock issued (in shares)						3,725,720
Warrants | Preferred Class A | Private Placement
Subsidiary, Sale of Stock [Line Items]
Sale of stock price (in usd per share) | $ / shares					$ 0.125
Warrants | Class A-3 Convertible Preferred Stock | Private Placement
Subsidiary, Sale of Stock [Line Items]
Sale of stock price (in usd per share) | $ / shares		$ 0.125
Certain Directors and Executive Officers | Private Placement
Subsidiary, Sale of Stock [Line Items]
Share sold (in shares)		833,208			526,083
Certain Directors and Executive Officers | Preferred Class A | Private Placement
Subsidiary, Sale of Stock [Line Items]
Warrants callable (in shares)					526,083
Proceeds from issuance of right to purchase common shares | $					$ 0.6
Certain Directors and Executive Officers | Class A-2 Convertible Preferred Stock | Milestone Closing
Subsidiary, Sale of Stock [Line Items]
Share sold (in shares)				121,581
Warrants callable (in shares)				1,215,810
Consideration received | $				$ 1
Certain Directors and Executive Officers | Class A-3 Convertible Preferred Stock | Private Placement
Subsidiary, Sale of Stock [Line Items]
Warrants callable (in shares)		624,906
Proceeds from issuance of right to purchase common shares | $		$ 0.6
Directors, Executive Officers and Employees | 2021 Closing
Subsidiary, Sale of Stock [Line Items]
Share sold (in shares)						2,222,222
Directors, Executive Officers and Employees | Class A-4 Convertible Preferred Stock | 2021 Closing
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of right to purchase common shares | $						$ 0.8
2019 Plan
Subsidiary, Sale of Stock [Line Items]
Number of additional shares authorized (in shares)			4,166,860
Number of years for increase of authorized shares			10 years
Number of additional shares authorized yearly increase			5.00%
Common stock available for future grant (in shares)							4,452,863
Total common shares reserved for future issuance (in shares)							13,871,693
Inducement Plan
Subsidiary, Sale of Stock [Line Items]
Common stock available for future grant (in shares)							1,800,000
Total common shares reserved for future issuance (in shares)	2,000,000						200,000
Vesting period	4 years
Inducement Plan | Share-based Payment Arrangement, Tranche One
Subsidiary, Sale of Stock [Line Items]
Award vesting percentage	25.00%
Inducement Plan | Share-based Payment Arrangement, Tranche Two
Subsidiary, Sale of Stock [Line Items]
Vesting period for remaining vesting rights	36 months

Stockholders' Equity (Share Act

Stockholders' Equity (Share Activity) (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Activity of Shares [Roll Forward]
Common stock, shares outstanding (in shares)	145,971,184
Common stock, shares outstanding (in shares)	145,981,180
Class A-1 Convertible Preferred Stock
Activity of Shares [Roll Forward]
Preferred stock, shares outstanding (in shares)	257,000	257,000
Conversions/Exercises (in shares)	0	0
Preferred stock, shares outstanding (in shares)	257,000	257,000
Class A-2 Convertible Preferred Stock
Activity of Shares [Roll Forward]
Preferred stock, shares outstanding (in shares)	1,331,000	1,416,000
Conversions/Exercises (in shares)	0	(78,000)
Preferred stock, shares outstanding (in shares)	1,331,000	1,338,000
Class A-3 Convertible Preferred Stock
Activity of Shares [Roll Forward]
Preferred stock, shares outstanding (in shares)	259,000	259,000
Conversions/Exercises (in shares)	0	0
Preferred stock, shares outstanding (in shares)	259,000	259,000
Class A-4 Convertible Preferred Stock
Activity of Shares [Roll Forward]
Preferred stock, shares outstanding (in shares)	3,725,720	0
Conversions/Exercises (in shares)	0	0
Preferred stock, shares outstanding (in shares)	3,725,720	0
Warrants
Activity of Shares [Roll Forward]
Warrants outstanding (in shares)	61,868,000	66,038,000
Conversions/Exercises (in shares)	0	(3,920,000)
Warrants outstanding (in shares)	61,868,000	62,118,000
Common Stock
Activity of Shares [Roll Forward]
Common stock, shares outstanding (in shares)
Conversions/Exercises (in shares)		3,199,000
Common stock, shares outstanding (in shares)

Stockholders' Equity (ATM Offer

Stockholders' Equity (ATM Offering) (Details) - At The Moment - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Aug. 10, 2021	Dec. 12, 2018
Class of Stock [Line Items]
Commission fee rate				3.00%
Share sold (in shares)	0	4,009,585
Consideration received		$ 5.8
Payments for commissions		$ 0.2
Amount eligible to be drawn down under the ATM	$ 50		$ 50

Stockholders' Equity (Common St

Stockholders' Equity (Common Stock Reserved for Future Issuance) (Details) shares in Thousands	Mar. 31, 2022shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock options outstanding (in shares)	12,846
Total common shares reserved for future issuance (in shares)	138,203
Common stock available for future grant under the 2019 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant (in shares)	4,453
Common stock available for future grant under the 2021 Inducement Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant (in shares)	1,800
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant (in shares)	291
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)	1,226
Class A-1 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	2,567
Class A-2 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	13,308
Class A-3 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	2,587
Class A-4 convertible preferred stock outstanding (as-converted)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares outstanding (in shares)	37,257
2019 PIPE Initial Closing warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	12,778
2019 PIPE Milestone Closing warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	30,595
2020 PIPE warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	18,495

Stockholders' Equity (Stock Opt

Stockholders' Equity (Stock Option and RSU Activity) (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Number of options
Ending outstanding number (in shares)	12,846
Stock options
Number of options
Beginning outstanding number (in shares)	8,661
Granted (in shares)	4,357
Canceled/forfeited/expired (in shares)	(172)
Ending outstanding number (in shares)	12,846
Weighted average exercise price
Beginning balance (in usd per share) | $ / shares	$ 1.17
Granted (in usd per share) | $ / shares	0.26
Canceled/forfeited/expired (in usd per share) | $ / shares	0.90
Ending balance (in usd per share) | $ / shares	$ 0.87
Restricted Stock Units (RSUs)
Number of RSUs
Beginning balance (in shares)	401
Shares granted (in shares)	848
Canceled/forfeited/expired (in shares)	(23)
Ending balance (in shares)	1,226
Weighted average grant date fair value
Beginning balance (in usd per share) | $ / shares	$ 0.95
Granted (in usd per share) | $ / shares	0.26
Canceled/forfeited/expired (in usd per share) | $ / shares	0.95
Ending balance (in usd per share) | $ / shares	$ 0.47

Stockholders' Equity (Assumptio

Stockholders' Equity (Assumptions Used to Estimate Fair Value of Stock Options and Performance Stock and Employee Stock Purchase Plan) (Details)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Stock options
Weighted average assumptions
Risk-free interest rate	1.70%	0.90%
Volatility	95.70%	95.70%
Dividend yield	0.00%	0.00%
Expected term (years)	6 years 1 month 6 days	6 years 1 month 6 days
Performance stock options
Weighted average assumptions
Risk-free interest rate	0.00%	1.00%
Volatility	0.00%	95.70%
Dividend yield	0.00%	0.00%
Expected term (years)	0 years	6 years 1 month 6 days
Employee stock purchase plan shares
Weighted average assumptions
Risk-free interest rate	0.30%	0.10%
Volatility	97.80%	101.30%
Dividend yield	0.00%	0.00%
Expected term (years)	6 months	6 months

Stockholders' Equity (Stock-Bas

Stockholders' Equity (Stock-Based Compensation Expense Allocation) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expenses	$ 1,000	$ 691
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expenses	270	181
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expenses	$ 730	$ 510

Collaborations (Details)

Collaborations (Details)	1 Months Ended							3 Months Ended		12 Months Ended
	Oct. 31, 2020USD ($)	Sep. 30, 2020USD ($)	Aug. 31, 2020USD ($)	Nov. 30, 2018USD ($)	Feb. 28, 2014USD ($)	Jun. 30, 2013USD ($)	Jul. 31, 2012target	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2019USD ($)	Nov. 30, 2020USD ($)
Revenue under collaborations
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues								$ 0	$ 0
Sanofi
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of collaborative areas granted | target							4
Initial upfront option payment	$ 4,000,000	$ 1,000,000	$ 1,000,000
Potential revenue through milestone payments				$ 6,800,000
Agreement period				24 months
Upfront payment non-creditable portion recognized										$ 6,800,000
Enrollment Milestone			10,000,000
Contract with customer, asset											$ 5,000,000
Development milestone not achievable								$ 25,000,000
Sanofi | Minimum | United States
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalties based on percentage of net sales								10.00%
Sanofi | Minimum | Outside of the United States
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalties based on percentage of net sales								10.00%
Sanofi | Maximum | United States
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalties based on percentage of net sales								20.00%
Sanofi | Maximum | Outside of the United States
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalties based on percentage of net sales								20.00%
Sanofi | Development Commercialization And License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue creditable against future milestones					$ 1,250,000			$ 1,250,000
Initial upfront option payment						$ 2,500,000
Sanofi | Proof-of-Concept Trial
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments								38,800,000
Sanofi | Clinical
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments								25,000,000
Sanofi | Regulatory and Commercialization Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments								$ 130,000,000
Sanofi | Development Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments			25,000,000	$ 40,000,000
Sanofi | Enrollment Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments				$ 10,000,000
Sanofi | Materials Sold
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments			4,000,000
Sanofi | Achievement of Enrollment Milestone
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential revenue through milestone payments			$ 5,000,000

Leases (Narrative) (Details)

Leases (Narrative) (Details) $ in Thousands	Feb. 11, 2021USD ($)ft²contract	Mar. 31, 2022USD ($)	Dec. 31, 2021USD ($)	Apr. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Jul. 01, 2019USD ($)	Jun. 19, 2019ft²
Lessee, Lease, Description [Line Items]
Remaining liability to be paid		$ 569
Base rent payments due 2021		776
ROU asset		2,436	$ 2,564
Operating lease payments due		$ 3,246
Prior Premises
Lessee, Lease, Description [Line Items]
Net rentable area | ft²							8,727
Term of contract			2 years 6 months
Remaining liability to be paid					$ 400
Base rent payments due 2021			$ 400
Initial direct cost liability						$ 800
ROU asset						600
Deferred credit, operating lease liabilities						$ 200
Campus Point Lease
Lessee, Lease, Description [Line Items]
Term of contract	60 months
Initial direct cost liability	$ 3,200			$ 100
ROU asset	3,000			100
Deferred credit, operating lease liabilities	$ 200
Rented area | ft²	13,438
Operating lease payments due	$ 3,800
Nonrefundable lease cost for assignment	$ 60
Number of operating lease contracts | contract	3
Deferred cost of liability				$ 200

Leases (Operating and Finance M

Leases (Operating and Finance Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remaining 2022	$ 569
2023	776
2024	800
2025	824
2026	277
Total operating lease payments	3,246
Less: amount representing interest	(380)
Present value of obligations under operating leases	2,866
Less: current portion	(604)
Long-term operating lease obligations	$ 2,262	$ 2,417