Regulus Therapeutics (RGLS) 10-Q 11 May 23 2023 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2023	May 05, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
Document Transition Report	false
Entity File Number	001-35670
Entity Registrant Name	Regulus Therapeutics Inc.
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		19,475,269
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001505512
Current Fiscal Year End Date	--12-31

CONDENSED BALANCE SHEETS

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 30,308	$ 24,228
Short-term investments	0	14,932
Restricted cash	62	62
Contract and other receivables	4	0
Prepaid materials, net	3,010	3,010
Prepaid expenses and other current assets	1,178	1,847
Total current assets	34,562	44,079
Property and equipment, net	493	536
Intangibles, net	58	62
Right of use asset	1,902	2,039
Total assets	37,015	46,716
Current liabilities:
Accounts payable	581	175
Accrued liabilities	671	961
Accrued research and development expenses	538	1,252
Accrued compensation	1,022	2,205
Current portion of term loan, less debt issuance costs	3,716	4,511
Other current liabilities	2,294	2,553
Total current liabilities	8,822	11,657
Lease liability, less current portion	1,598	1,768
Total liabilities	10,420	13,425
Commitments and Contingencies
Stockholders’ equity:
Common stock, $0.001 par value; 300,000,000 shares authorized at March 31, 2023 and December 31, 2022; 16,859,733 and 16,840,261 shares issued and outstanding at March 31, 2023 (unaudited) and December 31, 2022, respectively	17	17
Additional paid-in capital	516,888	516,457
Accumulated other comprehensive loss	0	(12)
Accumulated deficit	(490,315)	(483,176)
Total stockholders’ equity	26,595	33,291
Total liabilities and stockholders’ equity	37,015	46,716
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, 2023	Dec. 31, 2022
Common stock par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	16,859,733	16,840,261
Common stock, shares outstanding (in shares)	16,859,733	16,840,261
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, 2023	Mar. 31, 2022
Operating expenses:
Research and development	$ 4,925	$ 3,679
General and administrative	2,444	2,890
Total operating expenses	7,369	6,569
Loss from operations	(7,369)	(6,569)
Other income (expense):
Interest and other income	415	6
Interest and other expense	(185)	(155)
Loss before income taxes	(7,139)	(6,718)
Income tax expense	0	(1)
Net loss	(7,139)	(6,719)
Unrealized gain on short-term investments, net	12	0
Comprehensive loss	$ (7,127)	$ (6,719)
Net loss per share, basic (in usd per share)	$ (0.42)	$ (0.46)
Net loss per share, diluted (in usd per share)	$ (0.42)	$ (0.46)
Weighted average shares used to compute basic net loss per share (in shares)	16,844,243	14,596,789
Weighted average shares used to compute diluted net loss per share (in shares)	16,844,243	14,596,789

CONDENSED STATEMENTS OF CHANGES

CONDENSED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Preferred stock Convertible preferred stock	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Beginning balance, preferred stock shares (in shares) at Dec. 31, 2021		5,571,959
Beginning balance, common stock shares (in shares) at Dec. 31, 2021			14,597,118
Beginning balance at Dec. 31, 2021	$ 54,958	$ 5	$ 15	$ 509,791	$ 0	$ (454,853)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)			996
Issuance of common stock under Employee Stock Purchase Plan	2			2
Stock-based compensation expense	1,000			1,000
Gain on short-term investments	0
Net loss	(6,719)					(6,719)
Ending balance, preferred stock shares (in shares) at Mar. 31, 2022		5,571,959
Ending balance, common stock shares (in shares) at Mar. 31, 2022			14,598,114
Ending balance at Mar. 31, 2022	$ 49,241	$ 5	$ 15	510,793	0	(461,572)
Beginning balance, preferred stock shares (in shares) at Dec. 31, 2022		5,571,959
Beginning balance, common stock shares (in shares) at Dec. 31, 2022	16,840,261		16,840,261
Beginning balance at Dec. 31, 2022	$ 33,291	$ 5	$ 17	516,457	(12)	(483,176)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under Employee Stock Purchase Plan (in shares)			19,472
Issuance of common stock under Employee Stock Purchase Plan	21			21
Stock-based compensation expense	410			410
Gain on short-term investments	12				12
Net loss	$ (7,139)					(7,139)
Ending balance, preferred stock shares (in shares) at Mar. 31, 2023		5,571,959
Ending balance, common stock shares (in shares) at Mar. 31, 2023	16,859,733		16,859,733
Ending balance at Mar. 31, 2023	$ 26,595	$ 5	$ 17	$ 516,888	$ 0	$ (490,315)

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating activities
Net loss	$ (7,139)	$ (6,719)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization expense	48	26
Stock-based compensation	410	1,000
Amortization of premiums and accretion of discounts on investments, net	(56)	0
Other	31	38
Change in operating assets and liabilities:
Contracts and other receivables	(4)	(8)
Prepaid expenses and other assets	669	681
Accounts payable	406	340
Accrued liabilities	(290)	(26)
Accrued research and development expenses	(714)	(202)
Accrued compensation	(1,183)	(1,159)
Operating lease right-of-use assets and liabilities, net	(18)	(12)
Other liabilities	(274)	(340)
Net cash used in operating activities	(8,114)	(6,381)
Investing activities
Sales of short-term investments	15,000	0
Purchases of property and equipment	(1)	(102)
Net cash provided by (used in) investing activities	14,999	(102)
Financing activities
Proceeds from issuance of common stock, net	21	2
Principal payments on term loan	(826)	0
Net cash (used in) provided by financing activities	(805)	2
Net increase (decrease) in cash and cash equivalents	6,080	(6,481)
Cash and cash equivalents at beginning of period	24,290	60,445
Cash and cash equivalents at end of period	30,370	53,964
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	30,308	53,902
Restricted cash	62	62
Total cash, cash equivalents and restricted cash	30,370	53,964
Supplemental disclosure of cash flow information
Interest paid	(148)	(110)
Income taxes paid	0	(1)
Supplemental disclosure of non-cash investing and financing activities
Non-cash acquisition of property and equipment	$ 0	$ 33

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2023
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 8 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, 2022, from which the balance sheet information herein was derived. On June 24, 2022, we filed a Certificate of Amendment of Amended and Restated Certificate of Incorporation with the Secretary of State of the state of Delaware to effect a 1-for-10 reverse stock split of our issued and outstanding common stock. The primary purpose of the reverse stock split was to raise the per share trading price of our common stock to seek to maintain the listing of our common stock on The Nasdaq Capital Market. At the effective time of the reverse stock split, 5:00 p.m. on June 28, 2022, each 10 shares of our issued and outstanding common stock were automatically combined and converted into one issued and outstanding share of common stock. All of our stock options, restricted stock units ("RSUs") and warrants outstanding immediately prior to the reverse stock split, as well as the conversion ratio of our outstanding convertible preferred stock, were proportionately adjusted. All issued and outstanding common stock, options exercisable for common stock, restricted stock units, common stock issuable upon conversion of outstanding convertible preferred stock, warrants and per share amounts contained in our condensed financial statements have been retrospectively adjusted. Liquidity The accompanying financial statements have been prepared on a basis which assumes we are a going concern, and does not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classifications of liabilities that may result from any uncertainty related to our ability to continue as a going concern. 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 $556.6 million. As of March 31, 2023, we had approximately $30.3 million of cash and cash equivalents. Based on our operating plans, we believe our cash and cash equivalents may not be sufficient to fund our operations for the period one year following the issuance of these financial statements. Specifically, we believe these existing resources will only be sufficient to fund our planned operations and expenditures into mid-2024. Our current liquidity position, recurring losses from operations since inception and negative cash flows from operating activities raise substantial doubt about our ability to continue as a going concern. All amounts due under the Term Loan (see note 5) have been classified as a current liability as of March 31, 2023 due to the considerations discussed above and the assessment that the material adverse change clause under the Term Loan is not within our control. 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. If we are unable to continue as a going concern, we may have to liquidate our assets, and in doing so might realize significantly less for those assets than the values at which they are carried on our financial statements. Stockholders may lose all or part of their investment in our common stock. 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. 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. 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 progression through the various stages of our clinical trials. 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 have future use independent of the development status of any particular 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 Decem ber 15, 2022, with early adoption permitted. The adoption of this guidance had no impact on our financial statements and disclosures. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848), which provides guidance around reference rate reform initiatives to identify alternative reference rates that are more observable or transaction-based and less susceptible to manipulation in response to concerns about structural risks of interbank offered rates and the risk of cessation of the London Interbank Offered Rate ("LIBOR"). The amendments in the ASU provide option expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform and apply only if such contracts, hedging relationships and other transactions that reference LIBOR or another reference rate are expected to be discontinued because of reference rate reform. On December 21, 2022, the FASB issued ASU No. 2022-06, Reference Rate Reform (Topic 848): Deferral of the Sunset Date of Topic 848,

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic 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 equiva lents 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, warrants 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.

Investments

Investments	3 Months Ended
	Mar. 31, 2023
Debt Securities, Available-for-Sale [Abstract]
Investments	Investments Historically, 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, 2023, our cash balance was comprised entirely of cash and cash equivalents (money market funds) and there was no unrealized gain or loss in the period. Unrealized Maturity (in years) Amortized cost Gains Losses Estimated fair value As of December 31, 2022 U.S. Treasury securities 1 or less $ 14,944 $ (12) $ 14,932 $ 14,944 $ — $ (12) $ 14,932

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2023
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, 2023 and December 31, 2022 (in thousands): Fair value as of March 31, 2023 Total Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 29,271 $ 29,271 $ — $ — $ 29,271 $ 29,271 $ — $ — Fair value as of December 31, 2022 Total Level 1 Level 2 Level 3 Cash equivalents and short-term investments: Money market funds $ 21,490 $ 21,490 $ — $ — U.S. treasury securities 14,932 14,932 — — $ 36,422 $ 36,422 $ — $ —

Debt

Debt	3 Months Ended
	Mar. 31, 2023
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 ten times between October 2017 through August 2020. On December 31, 2021, we entered into an eleventh amendment to the Loan Agreement (the "Eleventh Amendment"). Under the terms of the Eleventh Amendment, the maturity date for the Term Loan was extended to May 1, 2024. In addition, under the Eleventh Amendment, our required monthly payments to the Lender were comprised of interest only through and including (i) December 1, 2022, if the 2022 Equity Event (as defined below) did not occur or (ii) December 1, 2023 if the 2022 Equity Event did occur. The “2022 Equity Event” meant 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. The 2022 Equity Event did not occur. 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, 2023, $3.9 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 current liabilities on our balance sheet at March 31, 2023). We had less than $0.1 million of debt issuance costs outstanding as of March 31, 2023, 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, 2023, future principal payments for the Term Loan due under the Loan Agreement are as follows (in thousands): 2023 $ 2,478 2024 1,377 $ 3,855

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock As of March 31, 2023, the re were 16,859,733 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. Reverse Stock Split On June 24, 2022, we filed a Certificate of Amendment of Amended and Restated Certificate of Incorporation with the Secretary of State of the state of Delaware to effect a 1-for-10 reverse stock split of our issued and outstanding common stock. The primary purpose of the reverse stock split was to raise the per share trading price of our common stock to seek to maintain the listing of our common stock on The Nasdaq Capital Market. At the effective time of the reverse stock split, 5:00 p.m. on June 28, 2022, each 10 shares of our issued and outstanding common stock were automatically combined and converted into one issued and outstanding share of common stock. All of our stock options, RSUs and warrants outstanding immediately prior to the reverse stock split, as well as the conversion ratio of our outstanding convertible preferred stock, were proportionately adjusted. All issued and outstanding common stock, options exercisable for common stock, restricted stock units, common stock issuable upon conversion of outstanding convertible preferred stock, warrants a nd per share amounts contained in these financial statements have been retrospectively adjusted. 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 with the 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 416,686 shares of common stock became available for issuance under the 2019 Plan pursuant to the second closing under our May 2019 securities purchase agreement. 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 Directors. As of March 31, 2023, 586,522 shares of common stock were available for new equity award grants under the 2019 Plan and 445,286 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 5635I(4) of the Nasdaq Listing Rules. The Inducement Plan initially reserved 200,000 shares of common stock and provides for the grant of non-qualified stock options 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. The authorized number of shares available for grant under the Inducement Plan was subsequently increased in October 2022 to 540,000 shares in the aggregate. Under the Inducement Plan, options are 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, 2023, 260,000 shares of common stock were reserved for future issuance under the Inducement Plan and 280,000 shares of common stock were reserved for future issuance pursuant to equity awards outstanding under the Inducement Plan. 2022 Employee Stock Purchase Plan In June 2022, our stockholders approved and we adopted the 2022 Employee Stock Purchase Plan (the “2022 Purchase Plan”), which enables participants to contribute up to 15% of such participant’s eligible compensation during a defined rolling six-month periods to purchase our common stock. The purchase price of common stock under the 2022 Purchase Plan will be the lesser of: (i) 85% of the fair market value of our common stock at the inception of the enrollment period or (ii) 85% of the fair market value of our common stock at the applicable purchase date. The 2022 Purchase Plan supersedes the 2012 Employee Stock Purchase Plan, and no further offerings will be made under the 2012 Employee Stock Purchase Plan. As of March 31 2023, a maximum of 159,635 shares of our common stock were reserved for future issuance and have been authorized for purchase under the 2022 Purchase Plan. 2021 Private Placement of Common Stock and Non-Voting Preferred Stock 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”), pursuant 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) 5,892,335 shares of common stock at a purchase price of $3.60 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 one share of common stock, subject to certain beneficial ownership conversion limitations. An aggregate of 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. Additional Outstanding Non-Voting Preferred Stock and Warrants In May 2019, we sold and issued (i) 973,045 shares of common stock (ii) 415,898 shares of non-voting Class A-1 convertible preferred stock and (iii) accompanying warrants to purchase an aggregate of 1,388,943 shares of common stock. Each share of non-voting Class A-1 convertible preferred stock is convertible into one share 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 $10.80 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events. The warrants are also exercisable on a net exercise "cashless" basis. In December 2019, we sold and issued 3,288,390 shares of non-voting Class A-2 convertible preferred stock and accompanying warrants to purchase an aggregate of 3,288,390 shares of common stock. Each share of non-voting Class A-2 convertible preferred stock is convertible into one share 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 $6.66 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events. The warrants are also exercisable on a net exercise “cashless” basis. In December 2020, we sold and issued (i) 2,434,152 shares of common stock (ii) 272,970 shares of non-voting Class A-3 convertible preferred stock and (iii) accompanying warrants to purchase an aggregate of 2,030,341 shares of common stock. Each share of non-voting Class A-3 convertible preferred stock is convertible into one share 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 $7.46 per share, subject to proportional adjustments in the event of stock splits or combinations or similar events. The warrants are also exercisable on a net exercise "cashless" basis. 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. 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. No shares were sold under the ATM Offering during the three months ended March 31, 2023 or 2022. At March 31, 2023, approximately $45.4 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, 2023 (in thousands): Class A-1 convertible preferred stock outstanding (as-converted) 257 Class A-2 convertible preferred stock outstanding (as-converted) 1,331 Class A-3 convertible preferred stock outstanding (as-converted) 259 Class A-4 convertible preferred stock outstanding (as-converted) 3,726 Warrants to purchase common stock 6,186 Common stock options outstanding 2,052 RSUs outstanding 210 Common stock available for future grant under the 2019 Equity Incentive Plan 656 Common stock available for future grant under the 2021 Inducement Plan 260 2022 Employee Stock Purchase Plan 160 Total common shares reserved for future issuance 15,097 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, 2023 (shares in thousands): Number of Weighted Number of Weighted average grant date fair value Stock Awards outstanding at December 31, 2022 1,372 $ 7.53 70 $ 2.57 Granted 762 $ 1.47 210 $ 1.48 Exercised (options) or Vested (RSUs) — $ — — $ — Canceled/forfeited/expired (82) $ 6.11 (70) $ 2.57 Stock Awards outstanding at March 31, 2023 2,052 $ 5.33 210 $ 1.48 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 2019 Equity Incentive Plan, 2021 Inducement Plan and the shares purchasable under our Employee Stock Purchase Plans during the periods presented: Three months ended 2023 2022 Stock options Risk-free interest rate 3.6 % 1.7 % Volatility 96.5 % 95.7 % Dividend yield — — Expected term (years) 6.1 6.1 Employee stock purchase plan shares Risk-free interest rate 4.0 % 0.3 % Volatility 104.4 % 97.8 % 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 2023 2022 Research and development $ 173 $ 270 General and administrative 237 730 Total $ 410 $ 1,000

Collaborations

Collaborations	3 Months Ended
	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaborations	Collaborations Sanofi In February 2014, we and Sanofi entered into a second amended and restated collaboration and license agreement (the “Sanofi Agreement”) to discover, develop and commercialize micro RNA therapeutics to focus on specific orphan disease and oncology targets. Under the terms of the Sanofi Agreement, Sanofi had opt-in rights to our clinical fibrosis program targeting miR-21 for the treatment of Alport syndrome (which rights were relinquished by Sanofi in November 2018), our preclinical program targeting miR-21 for oncology indications, and our preclinical program targeting miR-221/222 for 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. We were eligible to receive royalties on micro RNA therapeutic products commercialized by Sanofi and would have had have the right to co-promote these products relating to our preclinical program targeting miR-221/222.

Leases

Leases	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Leases	LeasesAt 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. Under the Campus Point Lease, we were required to maintain a deposit of $62,000 in a specially designated bank account, which we recorded as restricted cash on our balance sheet at March 31, 2023 and December 31, 2022. 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 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, 2023 are as follows (in thousands): Operating Leases Remaining 2023 $ 586 2024 800 2025 824 2026 277 Total operating lease payments $ 2,487 Less: amount representing interest (225) Present value of obligations under operating leases 2,262 Less: current portion (664) Long-term operating lease obligations $ 1,598

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2023
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event Private Placement of Common Stock and Non-Voting Preferred Stock On April 13, 2023, we entered into a Securities Purchase Agreement (the “April 2023 SPA”) with certain institutional and other accredited investors (the “2023 Purchasers”), pursuant to which we agreed to sell and issue shares of our common stock and shares of our newly designated non-voting convertible preferred stock in a private placement transaction. At the closing under the April 2023 SPA that occurred on April 13, 2023 (the “2023 Closing”), we sold and issued to the 2023 Purchasers (i) 2,615,536 shares of common stock at a purchase price of $0.9001 per share, and (ii) 140,827 shares of non-voting Class A-5 convertible preferred stock, in lieu of shares of common stock, at a price of $90.01 per share. Total gross proceeds from the 2023 Closing were approximately $15.0 million. Each share of non-voting Class A-5 convertible preferred stock is convertible into 100 shares of common stock, subject to certain beneficial ownership conversion limitations. An aggregate of 222,198 shares of common stock were purchased for $0.2 million by a director of the Company at the 2023 Closing.

Basis of Presentation and Sum_2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2023
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 8 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, 2022, from which the balance sheet information herein was derived. On June 24, 2022, we filed a Certificate of Amendment of Amended and Restated Certificate of Incorporation with the Secretary of State of the state of Delaware to effect a 1-for-10 reverse stock split of our issued and outstanding common stock. The primary purpose of the reverse stock split was to raise the per share trading price of our common stock to seek to maintain the listing of our common stock on The Nasdaq Capital Market. At the effective time of the reverse stock split, 5:00 p.m. on June 28, 2022, each 10 shares of our issued and outstanding common stock were automatically combined and converted into one issued and outstanding share of common stock. All of our stock options, restricted stock units ("RSUs") and warrants outstanding immediately prior to the reverse stock split, as well as the conversion ratio of our outstanding convertible preferred stock, were proportionately adjusted. All issued and outstanding common stock, options exercisable for common stock, restricted stock units, common stock issuable upon conversion of outstanding convertible preferred stock, warrants and per share amounts contained in our condensed financial statements have been retrospectively adjusted.
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
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.
Clinical Trial and Preclinical Study Accruals	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 progression through the various stages of our clinical trials. 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 have future use independent of the development status of any particular 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 Decem ber 15, 2022, with early adoption permitted. The adoption of this guidance had no impact on our financial statements and disclosures. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848), which provides guidance around reference rate reform initiatives to identify alternative reference rates that are more observable or transaction-based and less susceptible to manipulation in response to concerns about structural risks of interbank offered rates and the risk of cessation of the London Interbank Offered Rate ("LIBOR"). The amendments in the ASU provide option expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform and apply only if such contracts, hedging relationships and other transactions that reference LIBOR or another reference rate are expected to be discontinued because of reference rate reform. On December 21, 2022, the FASB issued ASU No. 2022-06, Reference Rate Reform (Topic 848): Deferral of the Sunset Date of 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.

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2023
Debt Securities, Available-for-Sale [Abstract]
Schedule of Debt Securities	Unrealized Maturity (in years) Amortized cost Gains Losses Estimated fair value As of December 31, 2022 U.S. Treasury securities 1 or less $ 14,944 $ (12) $ 14,932 $ 14,944 $ — $ (12) $ 14,932

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 and December 31, 2022 (in thousands): Fair value as of March 31, 2023 Total Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 29,271 $ 29,271 $ — $ — $ 29,271 $ 29,271 $ — $ — Fair value as of December 31, 2022 Total Level 1 Level 2 Level 3 Cash equivalents and short-term investments: Money market funds $ 21,490 $ 21,490 $ — $ — U.S. treasury securities 14,932 14,932 — — $ 36,422 $ 36,422 $ — $ —

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2023
Debt Disclosure [Abstract]
Debt Maturities	As of March 31, 2023, future principal payments for the Term Loan due under the Loan Agreement are as follows (in thousands): 2023 $ 2,478 2024 1,377 $ 3,855

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Common Stock Reserved for Future Issuance	The following shares of common stock were reserved for future issuance as of March 31, 2023 (in thousands): Class A-1 convertible preferred stock outstanding (as-converted) 257 Class A-2 convertible preferred stock outstanding (as-converted) 1,331 Class A-3 convertible preferred stock outstanding (as-converted) 259 Class A-4 convertible preferred stock outstanding (as-converted) 3,726 Warrants to purchase common stock 6,186 Common stock options outstanding 2,052 RSUs outstanding 210 Common stock available for future grant under the 2019 Equity Incentive Plan 656 Common stock available for future grant under the 2021 Inducement Plan 260 2022 Employee Stock Purchase Plan 160 Total common shares reserved for future issuance 15,097
Summary of Stock Option Activity RSU	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, 2023 (shares in thousands): Number of Weighted Number of Weighted average grant date fair value Stock Awards outstanding at December 31, 2022 1,372 $ 7.53 70 $ 2.57 Granted 762 $ 1.47 210 $ 1.48 Exercised (options) or Vested (RSUs) — $ — — $ — Canceled/forfeited/expired (82) $ 6.11 (70) $ 2.57 Stock Awards outstanding at March 31, 2023 2,052 $ 5.33 210 $ 1.48
Summary of 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 2019 Equity Incentive Plan, 2021 Inducement Plan and the shares purchasable under our Employee Stock Purchase Plans during the periods presented: Three months ended 2023 2022 Stock options Risk-free interest rate 3.6 % 1.7 % Volatility 96.5 % 95.7 % Dividend yield — — Expected term (years) 6.1 6.1 Employee stock purchase plan shares Risk-free interest rate 4.0 % 0.3 % Volatility 104.4 % 97.8 % Dividend yield — — Expected term (years) 0.5 0.5
Summary of 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 2023 2022 Research and development $ 173 $ 270 General and administrative 237 730 Total $ 410 $ 1,000

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Operating Lease, Liability, Maturity	Our future lease payments under operating leases at March 31, 2023 are as follows (in thousands): Operating Leases Remaining 2023 $ 586 2024 800 2025 824 2026 277 Total operating lease payments $ 2,487 Less: amount representing interest (225) Present value of obligations under operating leases 2,262 Less: current portion (664) Long-term operating lease obligations $ 1,598

Basis of Presentation and Sum_3

Basis of Presentation and Summary of Significant Accounting Policies (Details) $ in Millions		3 Months Ended
	Jun. 24, 2022	Mar. 31, 2023 USD ($)
Accounting Policies [Abstract]
Reverse stock split ratio	0.1
Financing from sale proceeds, debt, and agreement revenues		$ 556.6
Cash, cash equivalents and short-term investments		$ 30.3

Net Loss Per Share (Details)

Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Potentially dilutive securities not included in calculation of diluted net loss per share (in shares)	14,020,658	13,165,940

Investments (Details)

Investments (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized cost		$ 14,944,000
Unrealized gains		0
Unrealized losses		(12,000)
Estimated fair value		14,932,000
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized cost		14,944,000
Unrealized gains	$ 0
Unrealized losses	$ 0	(12,000)
Estimated fair value		$ 14,932,000

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	$ 29,271	$ 36,422
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	29,271	36,422
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
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	29,271	21,490
Money market funds | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	29,271	21,490
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
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
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis		14,932
U.S. Treasury securities | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis		14,932
U.S. Treasury securities | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis		0
U.S. Treasury securities | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis		$ 0

Debt (Narrative) (Details)

Debt (Narrative) (Details) $ in Millions			12 Months Ended	32 Months Ended
	Jun. 22, 2016 USD ($)	Jun. 17, 2016 payment	Dec. 31, 2022 USD ($)	May 31, 2020 amendment	Mar. 31, 2023 USD ($)
Debt Instrument [Line Items]
Number of times agreement was amended | amendment				10
Term Loan
Debt Instrument [Line Items]
Proceeds from borrowing under term loan	$ 20
Stated interest rate, percentage		8.51%
Number of monthly payments | payment		24
Debt fee					$ 1.3
Long-term debt					3.9
Other long-term liabilities					1.2
Debt issuance costs					$ 0.1
Debt instrument effective rate (as a percent)					8.98%
Term Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate, percentage		0.44%
Eleventh Amendment
Debt Instrument [Line Items]
Unrestricted net cash proceeds amount			$ 20
Cash collateral for borrowed securities					$ 5
Debt fee					$ 0.3

Debt (Future Principal Payments

Debt (Future Principal Payments) (Details) - Debt Financing Agreement Tranche A $ in Thousands	Mar. 31, 2023 USD ($)
Debt Instrument [Line Items]
2023	$ 2,478
2024	1,377
Long-term Debt	$ 3,855

Stockholders' Equity (Narrative

Stockholders' Equity (Narrative) (Details) $ / shares in Units, $ in Millions

1 Months Ended

Jun. 24, 2022

Nov. 23, 2021 shares

Jan. 22, 2020 shares

Jun. 30, 2022

Nov. 30, 2021 USD ($) $ / shares shares

Dec. 31, 2020 $ / shares shares

Dec. 31, 2019 $ / shares shares

May 31, 2019 $ / shares shares

Mar. 31, 2023 vote shares

Dec. 31, 2022 shares

Oct. 31, 2022 shares

Mar. 31, 2022 shares

Subsidiary, Sale of Stock [Line Items]

Common stock, shares outstanding (in shares)

16,859,733

16,840,261

Common stock voting rights votes | vote

1

Reverse stock split ratio

0.1

Total common shares reserved for future issuance (in shares)

15,097,000

2021 Closing

Subsidiary, Sale of Stock [Line Items]

Share sold (in shares)

5,892,335

Sale of stock price (in usd per share) | $ / shares

$ 3.60

Consideration received | $

$ 34.6

Shares issued upon conversion (in shares)

1

Private Placement

Subsidiary, Sale of Stock [Line Items]

Share sold (in shares)

2,434,152

973,045

Nonvoting convertible preferred stock issued (in shares)

415,898

Warrants callable (in shares)

2,030,341

Class of warrant

5 years

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

Class A-1 Convertible Preferred Stock | Private Placement

Subsidiary, Sale of Stock [Line Items]

Warrants callable (in shares)

1,388,943

Preferred Class A | Private Placement

Subsidiary, Sale of Stock [Line Items]

Sale of stock price (in usd per share) | $ / shares

$ 10.80

Shares issued upon conversion (in shares)

1

Class A-2 Convertible Preferred Stock | 2019 PIPE Milestone Closing warrants

Subsidiary, Sale of Stock [Line Items]

Share sold (in shares)

3,288,390

Shares issued upon conversion (in shares)

1

Warrants callable (in shares)

3,288,390

Class of warrant

5 years

Warrant exercise price (in usd per share) | $ / shares

$ 6.66

Class A-3 Convertible Preferred Stock | Private Placement

Subsidiary, Sale of Stock [Line Items]

Nonvoting convertible preferred stock issued (in shares)

272,970

Shares issued upon conversion (in shares)

1

Class of warrant

5 years

Warrant exercise price (in usd per share) | $ / shares

$ 7.46

Directors, Executive Officers and Employees | 2021 Closing

Subsidiary, Sale of Stock [Line Items]

Share sold (in shares)

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)

416,686

Number of years for increase of authorized shares

10 years

Number of additional shares authorized yearly increase (as a percent)

5%

Common stock available for future grant (in shares)

586,522

Total common shares reserved for future issuance (in shares)

445,286

Inducement Plan

Subsidiary, Sale of Stock [Line Items]

Common stock available for future grant (in shares)

260,000

Total common shares reserved for future issuance (in shares)

200,000

280,000

540,000

Vesting period

4 years

Inducement Plan | Share-based Payment Arrangement, Tranche One

Subsidiary, Sale of Stock [Line Items]

Award vesting percentage

25%

Inducement Plan | Share-based Payment Arrangement, Tranche Two

Subsidiary, Sale of Stock [Line Items]

Vesting period for remaining vesting rights

36 months

Employee Stock Purchase Plan Two Thousand Twelve | 2022 Employee Stock Purchase Plan

Subsidiary, Sale of Stock [Line Items]

Share-based compensation arrangement by share-based payment award, discount from market price, purchase date

15%

Share-based compensation arrangement by share-based payment award, purchase price of common stock, percent

85%

Share-based compensation arrangement by share-based payment award, number of shares authorized (in shares)

159,635

Stockholders' Equity (ATM Offer

Stockholders' Equity (ATM Offering) (Details) - At The Moment - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2021	Sep. 30, 2022	Aug. 10, 2021	Dec. 12, 2018
Class of Stock [Line Items]
Commission fee rate (as a percent)				3%
Share sold (in shares)	0
Amount eligible to be drawn down under the ATM		$ 45.4	$ 50

Stockholders' Equity (Common St

Stockholders' Equity (Common Stock Reserved for Future Issuance) (Details) shares in Thousands	Mar. 31, 2023 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock options outstanding (in shares)	2,052
Total common shares reserved for future issuance (in shares)	15,097
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)	656
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)	260
2022 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for future grant (in shares)	160
RSUs outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs outstanding (in shares)	210
Warrants to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants outstanding (in shares)	6,186
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)	257
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)	1,331
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)	259
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)	3,726

Stockholders' Equity (Stock Opt

Stockholders' Equity (Stock Option and RSU Activity) (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2023 $ / shares shares
Number of options
Ending balance (in shares)	2,052
Stock options
Number of options
Beginning balance (in shares)	1,372
Granted (in shares)	762
Exercised (options) or Vested (RSUs)	0
Canceled/forfeited/expired (in shares)	(82)
Ending balance (in shares)	2,052
Weighted average exercise price
Beginning balance (in usd per share) | $ / shares	$ 7.53
Granted (in usd per share) | $ / shares	1.47
Exercised (options) or Vested (RSUs) (in usd per share) | $ / shares	0
Canceled/forfeited/expired (in usd per share) | $ / shares	6.11
Ending balance (in usd per share) | $ / shares	$ 5.33
Restricted Stock Units (RSUs)
Number of RSUs
Beginning balance (in shares)	70
Shares granted (in shares)	210
Exercised (options) or Vested (RSUs) (in shares)	0
Canceled/forfeited/expired (in shares)	(70)
Ending balance (in shares)	210
Weighted average grant date fair value
Beginning balance (in usd per share) | $ / shares	$ 2.57
Granted (in usd per share) | $ / shares	1.48
Exercised (options) or Vested (RSUs) (in usd per share) | $ / shares	0
Canceled/forfeited/expired (in usd per share) | $ / shares	2.57
Ending balance (in usd per share) | $ / shares	$ 1.48

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, 2023	Mar. 31, 2022
Stock options
Weighted average assumptions
Risk-free interest rate	3.60%	1.70%
Volatility	96.50%	95.70%
Dividend yield	0%	0%
Expected term (years)	6 years 1 month 6 days	6 years 1 month 6 days
Employee stock purchase plan shares
Weighted average assumptions
Risk-free interest rate	4%	0.30%
Volatility	104.40%	97.80%
Dividend yield	0%	0%
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, 2023	Mar. 31, 2022
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expenses	$ 410	$ 1,000
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expenses	173	270
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expenses	$ 237	$ 730

Leases (Narrative) (Details)

Leases (Narrative) (Details) $ in Thousands	Feb. 11, 2021 USD ($) ft² contract	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Apr. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jul. 01, 2019 USD ($)	Jun. 19, 2019 ft²
Lessee, Lease, Description [Line Items]
Remaining liability to be paid		$ 586
Base rent payments due 2021		800
ROU asset		1,902	$ 2,039
Operating lease payments due		2,487
Restricted cash		62	62	$ 62
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
Restricted cash		$ 62	$ 62

Leases (Operating and Finance M

Leases (Operating and Finance Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Remaining 2023	$ 586
2024	800
2025	824
2026	277
Total operating lease payments	2,487
Less: amount representing interest	(225)
Present value of obligations under operating leases	2,262
Less: current portion	(664)
Long-term operating lease obligations	$ 1,598	$ 1,768

Subsequent Event (Details)

Subsequent Event (Details) - 2023 Closing - Subsequent Event $ / shares in Units, $ in Millions	Apr. 13, 2023 USD ($) $ / shares shares
Subsequent Event [Line Items]
Consideration received | $	$ 15
Director
Subsequent Event [Line Items]
Share sold (in shares)	222,198
Common stock
Subsequent Event [Line Items]
Share sold (in shares)	2,615,536
Sale of stock price (in usd per share) | $ / shares	$ 0.9001
Shares issued upon conversion (in shares)	100
Class A-5 Convertible Preferred Stock
Subsequent Event [Line Items]
Share sold (in shares)	140,827
Sale of stock price (in usd per share) | $ / shares	$ 90.01
Class A-4 Convertible Preferred Stock | Director
Subsequent Event [Line Items]
Consideration received | $	$ 0.2