0000950170-22-016017 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2022	Aug. 08, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Trading Symbol	SCPH
Entity Registrant Name	SCPHARMACEUTICALS INC.
Entity Central Index Key	0001604950
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Current Reporting Status	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common stock, par value $0.0001
Security Exchange Name	NASDAQ
Entity File Number	001-38293
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-5184075
Entity Address, Address Line One	2400 District Avenue
Entity Address, Address Line Two	Suite 310
Entity Address, City or Town	Burlington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01803
City Area Code	617
Local Phone Number	517-0730
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		27,402,121

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets
Cash and cash equivalents	$ 41,178	$ 74,268
Restricted cash		182
Short-term investments	14,673	1,010
Prepaid expenses	1,673	2,791
Other current assets	331	24
Total current assets	57,855	78,275
Restricted cash	182
Property and equipment, net	57	69
Right-of-use lease assets - operating, net	785	410
Deposits and other assets	283	283
Total assets	59,162	79,037
Current liabilities
Accounts payable	982	544
Accrued expenses	4,126	3,995
Term loan, short-term	9,851	9,805
Lease obligation - operating, short-term	553	476
Other current liabilities	28	26
Total current liabilities	15,540	14,846
Term loan, long-term	2,463	7,354
Lease obligation - operating, long-term	271
Other liabilities	431	367
Total liabilities	18,705	22,567
Commitments and contingencies (Note 11)
Stockholders’ equity
Preferred stock, $0.0001 par value; 10,000,000 shares authorized and no shares issued and outstanding
Common stock, $0.0001 par value; 150,000,000 shares authorized as of June 30, 2022; 27,366,707 and 27,395,146 shares issued and outstanding as of December 31, 2021 and June 30, 2022, respectively	3	3
Additional paid-in capital	247,587	246,166
Accumulated deficit	(207,126)	(189,698)
Accumulated other comprehensive loss	(7)	(1)
Total stockholders’ equity	40,457	56,470
Total liabilities and stockholders’ equity	$ 59,162	$ 79,037

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	27,395,146	27,366,707
Common stock, shares outstanding	27,395,146	27,366,707

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating expenses:
Research and development	$ 5,142	$ 3,807	$ 9,489	$ 7,816
General and administrative	4,279	2,649	7,172	5,381
Total operating expenses	9,421	6,456	16,661	13,197
Loss from operations	(9,421)	(6,456)	(16,661)	(13,197)
Other income	64	33	78	288
Interest income	107	12	120	32
Interest expense	(447)	(651)	(965)	(1,287)
Net loss	$ (9,697)	$ (7,062)	$ (17,428)	$ (14,164)
Net loss per share - basic	$ (0.35)	$ (0.26)	$ (0.64)	$ (0.52)
Net loss per share - diluted	$ (0.35)	$ (0.26)	$ (0.64)	$ (0.52)
Weighted average common shares outstanding - basic	27,378,507	27,355,454	27,373,459	27,346,141
Weighted average common shares outstanding - diluted	27,378,507	27,355,454	27,373,459	27,346,141
Other comprehensive loss:
Unrealized gain (loss) on short-term investments	$ (3)	$ 1	$ (6)	$ (1)
Comprehensive loss	$ (9,700)	$ (7,061)	$ (17,434)	$ (14,165)

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Other Comprehensive Income
Beginning Balance at Dec. 31, 2020	$ 82,170	$ 3	$ 243,830	$ (161,664)	$ 1
Beginning Balance, Shares at Dec. 31, 2020		27,325,959
Net loss	(7,102)			(7,102)
Issuance of common stock upon exercise of stock options	9		9
Issuance of common stock upon exercise of stock options, Shares		2,500
Vesting of restricted stock	(81)		(81)
Vesting of restricted stock, Shares		26,994
Stock-based compensation	521		521
Unrealized gain (loss) on short-term investments	(2)				(2)
Ending Balance at Mar. 31, 2021	75,515	$ 3	244,279	(168,766)	(1)
Ending Balance, Shares at Mar. 31, 2021		27,355,453
Beginning Balance at Dec. 31, 2020	82,170	$ 3	243,830	(161,664)	1
Beginning Balance, Shares at Dec. 31, 2020		27,325,959
Net loss	(14,164)
Unrealized gain (loss) on short-term investments	(1)
Ending Balance at Jun. 30, 2021	69,043	$ 3	244,868	(175,828)
Ending Balance, Shares at Jun. 30, 2021		27,355,454
Beginning Balance at Mar. 31, 2021	75,515	$ 3	244,279	(168,766)	(1)
Beginning Balance, Shares at Mar. 31, 2021		27,355,453
Net loss	(7,062)			(7,062)
Issuance of common stock upon exercise of stock options, Shares		1
Stock-based compensation	589		589
Unrealized gain (loss) on short-term investments	1				1
Ending Balance at Jun. 30, 2021	69,043	$ 3	244,868	(175,828)
Ending Balance, Shares at Jun. 30, 2021		27,355,454
Beginning Balance at Dec. 31, 2021	56,470	$ 3	246,166	(189,698)	(1)
Beginning Balance, Shares at Dec. 31, 2021		27,366,707
Net loss	(7,731)			(7,731)
Issuance of common stock upon exercise of stock options	21		21
Issuance of common stock upon exercise of stock options, Shares		4,781
Stock-based compensation	636		636
Unrealized gain (loss) on short-term investments	(3)				(3)
Ending Balance at Mar. 31, 2022	49,393	$ 3	246,823	(197,429)	(4)
Ending Balance, Shares at Mar. 31, 2022		27,371,488
Beginning Balance at Dec. 31, 2021	56,470	$ 3	246,166	(189,698)	(1)
Beginning Balance, Shares at Dec. 31, 2021		27,366,707
Net loss	$ (17,428)
Issuance of common stock upon exercise of stock options, Shares	4,781
Unrealized gain (loss) on short-term investments	$ (6)
Ending Balance at Jun. 30, 2022	40,457	$ 3	247,587	(207,126)	(7)
Ending Balance, Shares at Jun. 30, 2022		27,395,146
Beginning Balance at Mar. 31, 2022	49,393	$ 3	246,823	(197,429)	(4)
Beginning Balance, Shares at Mar. 31, 2022		27,371,488
Net loss	(9,697)			(9,697)
Issuance of common stock through employee stock purchase plan	84		84
Issuance of common stock through employee stock purchase plan, Shares		23,658
Stock-based compensation	680		680
Unrealized gain (loss) on short-term investments	(3)				(3)
Ending Balance at Jun. 30, 2022	$ 40,457	$ 3	$ 247,587	$ (207,126)	$ (7)
Ending Balance, Shares at Jun. 30, 2022		27,395,146

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities
Net loss	$ (17,428,000)	$ (14,164,000)
Adjustments to reconcile net loss to cash used in operating activities
Depreciation expense	18,000	16,000
Amortization expense - right-of-use leased assets - operating	212,000	199,000
Accretion of discount on investments	(24,000)	115,000
Stock-based compensation	1,316,000	1,110,000
Non-cash interest expense	218,000	263,000
Changes in operating assets and liabilities
Prepaid expenses and other assets	809,000	143,000
Accounts payable, accrued expenses and other liabilities	335,000	(2,568,000)
Net cash used in operating activities	(14,544,000)	(14,886,000)
Cash flows from investing activities
Purchases of property and equipment	(6,000)
Maturities of short-term investments	7,000,000	26,100,000
Purchases of short-term investments	(20,645,000)	(7,992,000)
Net cash provided by (used in) investing activities	(13,651,000)	18,108,000
Cash flows from financing activities
Principal payments on term loan	(5,000,000)
Proceeds from employee stock purchase plan	84,000
Proceeds from the exercise of vested stock options	21,000	9,000
Settlements of restricted stock units for tax withholding obligations		(81,000)
Net cash used in financing activities	(4,895,000)	(72,000)
Net increase (decrease) in cash, cash equivalents and restricted cash	(33,090,000)	3,150,000
Cash, cash equivalents and restricted cash at beginning of period	74,450,000	72,001,000
Cash, cash equivalents and restricted cash at end of period	41,360,000	75,151,000
Supplemental cash flow information
Interest paid	794,000	1,114,000
Taxes paid	$ 114,000	$ 125,000

Description of Business and Basis of Presentation

6 Months Ended

Jun. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of Business and Basis of Presentation

1. Description of Business and Basis of Presentation

Description of Business

scPharmaceuticals LLC was formed as a limited liability company under the laws of the State of Delaware on February 19, 2013. On March 24, 2014, scPharmaceuticals LLC was converted to a Delaware corporation and changed its name to scPharmaceuticals Inc. (“the Company”). The Company is a pharmaceutical company focused on developing and commercializing products that have the potential to optimize the delivery of infused therapies, advance patient care and reduce healthcare costs. The Company’s strategy is designed to enable the subcutaneous administration of therapies that have previously been limited to intravenous (“IV”) delivery. The Company’s headquarters and primary place of business is Burlington, Massachusetts.

Basis of Presentation

The accompanying condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States (“U.S. GAAP”) for interim financial information and have been prepared on a basis which assumes that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. The condensed consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary, scPharmaceuticals Securities Corporation. Certain information and disclosures normally included in financial statements in accordance with U.S. GAAP have been condensed or omitted. Accordingly, these condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements and related notes for the year ended December 31, 2021 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on March 22, 2022. The Company has determined that it operates in one segment.

The accompanying condensed consolidated balance sheet as of June 30, 2022, the condensed consolidated statements of operations and comprehensive loss and stockholders’ equity for the three and six months ended June 30, 2021 and 2022 and condensed consolidated statements of cash flows for the six months ended June 30, 2021 and 2022 are unaudited. The unaudited condensed consolidated financial statements have been prepared on a basis consistent with that used to prepare the Company’s audited annual financial statements and include, in the opinion of management, adjustments, consisting of normal recurring items, necessary for the fair statement of the condensed consolidated financial statements. The operating results for the three and six months ended June 30, 2022 are not necessarily indicative of the results expected for the full year ending December 31, 2022.

Liquidity

As of June 30, 2022, the Company had an accumulated deficit of approximately $207.1 million. Management expects to continue to incur operating losses for the foreseeable future. The Company has financed its operations to date from proceeds from the sale of common stock, preferred stock and the incurrence of debt.

As of June 30, 2022, the Company had cash, cash equivalents, restricted cash, and short-term investments of $56.0 million. The Company's existing cash, cash equivalents, restricted cash and short-term investments will be sufficient to meet its cash commitments for at least the next 12 months after the date that the interim condensed consolidated financial statements are issued. Additionally, the Company expects to have access to funds pursuant to an at-the-market offering program with Cowen and Company, LLC (Note 9), or could otherwise seek additional funding through a combination of public or private equity offerings or debt financing if it believes additional resources are needed. Additional financing may not be available on a timely basis on terms acceptable to the Company, or at all.

Significant Accounting Policies

6 Months Ended

Jun. 30, 2022

Accounting Policies [Abstract]

Significant Accounting Policies

2. Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reported periods. Actual results could differ from those estimates.

Cash, Cash Equivalents and Restricted Cash

Cash, cash equivalents and restricted cash consists of bank deposits and money market accounts with financial institutions. Cash equivalents are carried at cost which approximates fair value due to their short-term nature and which the Company believes do not have a material exposure to credit risk. The Company considers all highly liquid investments with maturities of three months or less from the date of purchase to be cash equivalents. The Company’s cash and cash equivalent accounts, at times, may exceed federally insured limits. The Company has not experienced any losses in such accounts.

As of June 30, 2022, the Company classified $182,000 as restricted cash related to a letter of credit issued as a security deposit in connection with the Company’s lease of its corporate office facilities (Note 11). Cash, cash equivalents and restricted cash consists of the following (in thousands):


	December 31, 2021		June 30, 2022
Cash and cash equivalents	$	74,268	$	41,178
Restricted cash		182		182
Cash, cash equivalents and restricted cash	$	74,450	$	41,360

Concentration of Credit Risk

Financial instruments that subject the Company to credit risk primarily consist of cash and cash equivalents and short-term investments. The Company maintains its cash and cash equivalent balances with high-quality financial institutions and, consequently, the Company believes that such funds are subject to minimal credit risk. The Company’s short-term investments consist of United States Treasury securities, corporate debt securities and commercial paper. The Company has adopted an investment policy that limits the amounts the Company may invest in any one type of investment and requires all investments held by the Company to hold a minimum rating, thereby reducing credit risk exposure.

Investments

The Company invests excess cash balances in available-for-sale debt securities. The Company determines the appropriate classification of these securities at the time they are acquired and evaluates the appropriateness of such classifications at each balance sheet date. The Company reports available-for-sale investments at fair value at each balance sheet date and includes any unrealized gains and losses in accumulated other comprehensive income (loss), a component of stockholders’ equity. Realized gains and losses are determined using the specific identification method and are included in other income (expense). If any adjustment to fair value reflects a decline in the value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other than temporary,” including the intention to sell and, if so, marks the investment to market through a charge to the Company’s consolidated statements of operations and comprehensive loss.

Leases

The Company determines if an arrangement is a lease at inception. Operating leases are included in right-of-use (“ROU”) lease assets, current portion of lease obligations, and long-term lease obligations on the Company’s balance sheets.

ROU lease assets represent the Company’s right to use an underlying asset for the lease term and lease obligations represent the Company’s obligation to make lease payments arising from the lease. Operating ROU lease assets and obligations are recognized at the commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The ROU lease asset excludes lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term.

Income Taxes

The Company accounts for income taxes in accordance with the Financial Accounting Standards Board’s (“FASB”) Accounting Standards Codification (“ASC”) 740, Income Taxes. Deferred tax assets and liabilities are recorded to reflect the impact of temporary differences between amounts of assets and liabilities for financial reporting purposes and such amounts as measured under enacted tax laws. A valuation allowance is required to offset any net deferred tax assets if, based upon the available evidence, it is more likely than not that some or all of the deferred tax asset will not be realized.

The Company provides reserves for potential payments of tax to various tax authorities related to uncertain tax positions. The tax benefits recorded are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is “more likely than not” to be realized following resolution of any uncertainty related to the tax benefit, assuming that the matter in question will be raised by the tax authorities. Potential interest and penalties associated with such uncertain tax positions are recorded as a component of income tax expense. At June 30, 2022, the Company had no such accruals.

As part of the Tax Cuts and Jobs Act of 2017 (TCJA), beginning with the Company’s fiscal year ending December 31, 2022, the Company is required to capitalize research and development expenses, as defined under section 174 of the Internal Revenue Code of 1986, as amended. For expenses that are incurred for research and development in the United States, the amounts will be amortized over 5 years, and expenses that are incurred for research and experimentation outside the United States will be amortized over 15 years. The Company already capitalizes its research and development expenses for income tax purposes as it is a start-up company, so there is no material impact forecasted for this change in legislation in 2022.

Net Loss per Share

6 Months Ended

Jun. 30, 2022

Earnings Per Share [Abstract]

Net Loss per Share

3. Net Loss per Share

Net Loss per Share Attributable to Common Stockholders

The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except share and per share data):


	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2022			2021			2022
Net loss	$	(7,062	)	$	(9,697	)	$	(14,164	)	$	(17,428	)
Weighted-average shares used in computing net loss per share		27,355,454			27,378,507			27,346,141			27,373,459
Net loss per share, basic and diluted	$	(0.26	)	$	(0.35	)	$	(0.52	)	$	(0.64	)

The Company’s potentially dilutive securities, which include stock options and unvested restricted stock units, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect.


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2022		2021		2022
Stock options to purchase common stock		2,677,368		3,771,435		2,677,368		3,771,435
Unvested restricted stock units		42,250		42,250		42,250		42,250
Total		2,719,618		3,813,685		2,719,618		3,813,685

Investments

6 Months Ended

Jun. 30, 2022

Investments, Debt and Equity Securities [Abstract]

Investments

4. Investments

Cash in excess of the Company’s immediate requirements is invested in accordance with the Company’s investment policy that primarily seeks to maintain adequate liquidity and preserve capital.

A summary of the Company’s available-for-sale classified investments as of December 31, 2021 and June 30, 2022 consisted of the following (in thousands):


	At December 31, 2021
Investments - Current:	Cost Basis		Accumulated Unrealized Gains		Accumulated Unrealized Losses			Fair Value
Corporate debt securities	$	1,011	$	-	$	(1	)	$	1,010
Total	$	1,011	$	-	$	(1	)	$	1,010


	At June 30, 2022
Investments - Current:	Cost Basis		Accumulated Unrealized Gains		Accumulated Unrealized Losses			Fair Value
United States Treasury securities	$	9,992	$	-	$	(6	)	$	9,986
Corporate debt securities		1,801		-		(1	)		1,800
Commercial paper		2,887		-		-			2,887
Total	$	14,680	$	-	$	(7	)	$	14,673

The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of June 30, 2022 consisted of the following (in thousands):


	Amortized Cost		Fair Value
Due in one year or less	$	14,680	$	14,673
Total	$	14,680	$	14,673

Property and Equipment

6 Months Ended

Jun. 30, 2022

Property, Plant and Equipment [Abstract]

Property and Equipment

5. Property and Equipment

Purchased property and equipment consist of the following (dollars in thousands):


	ESTIMATED USEFUL LIFE	December 31, 2021			June 30, 2022
Office equipment	5 years	$	10		$	6
Office furniture	7 years		126			126
Computer equipment	3 years		8			8
Leasehold improvements	Life of lease		95			95
			239			235
Less: Accumulated depreciation			(170	)		(178	)
Property and equipment, net		$	69		$	57

Depreciation expense for the three months ended June 30, 2021 and June 30, 2022 was $8,000 and $9,000, respectively.

Depreciation expense for the six months ended June 30, 2021 and June 30, 2022 was $16,000 and $18,000, respectively.

Accrued Expenses

6 Months Ended

Jun. 30, 2022

Accrued Liabilities, Current [Abstract]

Accrued Expenses

6. Accrued Expenses

Accrued expenses consist of the following (in thousands):


	December 31, 2021		June 30, 2022
Contract research and development	$	2,350	$	2,162
Employee compensation and related costs		1,152		1,412
Consulting and professional service fees		265		386
Interest		154		106
Financing related costs		60		60
State taxes		5		—
Other		9		—
Total accrued expenses	$	3,995	$	4,126

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2022

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

7. Fair Value of Financial Instruments

FASB ASC Topic, Fair Value Measurements and Disclosures (“ASC 820”), provides a fair value hierarchy, which classifies fair value measurements based on the inputs used in measuring fair value. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below:

Level 1—Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date.

Level 2—Valuations based on quoted prices for similar assets or liabilities in markets that are not active or for which all significant inputs are observable, either directly or indirectly.

Level 3—Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and observable.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

The carrying values of the Company’s cash and restricted cash, prepaid expenses and deposits approximate their fair values due to their short-term nature. The carrying value of the Company’s loan payable is considered a reasonable estimate of fair value because the Company’s interest rate is near current market rates for instruments with similar characteristics.

The following tables summarize the Company’s assets that are measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands):


	As of December 31, 2021
	TOTAL		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	72,449	$	72,449	$	—	$	—
Total cash equivalents		72,449		72,449		—		—

Corporate debt securities		1,010		—		1,010		—
Investments		1,010		—		1,010		—

Total	$	73,459	$	72,449	$	1,010	$	—


	As of June 30, 2022
	TOTAL		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	39,381	$	38,381	$	1,000	$	—
Total cash equivalents		39,381		38,381		1,000		—

United States Treasury securities		9,986		9,986		—		—
Corporate debt securities		1,800		—		1,800		—
Commercial paper		2,887		—		2,887		—
Investments		14,673		9,986		4,687		—

Total	$	54,054	$	48,367	$	5,687	$	—

- Definition

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

+ References + Details

Term Loan

6 Months Ended

Jun. 30, 2022

Debt Disclosure [Abstract]

Term Loan

8. Term Loan

In May 2017, the Company entered into a loan and security agreement (the “2017 Loan Agreement”), with SLR Investment Corp. (f/k/a Solar Capital Ltd.) and Silicon Valley Bank (together, the “Lenders”), for $10.0 million.

In September 2019, the Company replaced the 2017 Loan Agreement with a new $20.0 million term loan with the Lenders (the “2019 Loan Agreement”). The 2019 Loan Agreement extends the term of the credit facility until September 17, 2023. Debt issuance costs for the 2019 Loan Agreement, including unamortized issuance costs for the 2017 Loan Agreement, will be amortized to interest expense over the remaining term of the 2019 Loan Agreement using the effective-interest method.

The interest rate under the 2019 Loan Agreement is the higher of (i) LIBOR plus 7.95% or (ii) 10.18% and there was an interest-only period until September 30, 2021. The rate at June 30, 2022 was 10.18%. Pursuant to the 2019 Loan Agreement, the Company provided a first priority security interest in substantially all of the Company’s assets, including intellectual property, subject to certain exceptions.

The Company entered into an Exit Agreement in connection with the 2019 Loan Agreement which provides for an aggregate payment of 4% of the loan commitment, or $800,000, to the lenders upon the occurrence of an exit event (the “Exit Fee”). The Company paid the Exit Fee during 2020 in conjunction with the Company’s public offering, which was deemed to be an exit event pursuant to the Exit Agreement.

As of June 30, 2022, unpaid borrowings under the 2019 Loan Agreement totaled $12.5 million. For the three and six months ended June 30, 2022, the Company recorded $74,000 and $155,000, respectively, related to the amortization of debt discount associated with the 2019 Loan Agreement. For the three and six months ended June 30, 2021, the Company recorded $95,000 and $182,000, respectively, related to the amortization of debt discount associated with the 2019 Loan Agreement.

The 2019 Loan Agreement allows the Company to voluntarily prepay all (but not less than all) of the outstanding principal at any time. A prepayment premium of 3% or 1% through the one-year anniversary and the two-year anniversary, respectively, would be assessed on the outstanding principal. After the two-year anniversary, a 0.5% prepayment premium would be assessed on the outstanding principal. A final payment fee of $500,000 is due upon the earlier to occur of the maturity date or prepayment of such borrowings. For the three and six months ended June 30, 2022, the Company recorded $29,000 and $63,000, respectively, related to the amortization of the final payment fee associated with the 2019 Loan Agreement. For the three and six months ended June 30, 2021, the Company recorded $41,000 and $81,000, respectively, related to the amortization of the final payment fee associated with the 2019 Loan Agreement.

In an event of default under the 2019 Loan Agreement, the interest rate will be increased by 5% and the balance under the loan may become immediately due and payable at the option of the lenders.

The 2019 Loan Agreement includes restrictions on, among other things, the Company’s ability to incur additional indebtedness, change the name or location of the Company’s business, merge with or acquire other entities, pay dividends or make other distributions to holders of its capital stock, make certain investments, engage in transactions with affiliates, create liens, sell assets or pay subordinated debt.

Total term loan and unamortized debt discount balances are as follows (in thousands):


	June 30, 2022
Face value	$	12,500
Less: discount		(186	)
Total	$	12,314
Less: current portion		(9,851	)
Long-term portion	$	2,463

As of June 30, 2022, future principal payments due under the 2019 Loan Agreement are as follows (in thousands):


Year ended:
December 31, 2022	$	5,000
December 31, 2023		7,500
Total	$	12,500

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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+ Details

Stockholders' Equity

6 Months Ended

Jun. 30, 2022

Equity [Abstract]

Stockholders' Equity

9. Stockholders’ Equity

2021 At-the-Market Issuance Sales Agreement

On March 23, 2021, the Company entered into a Sales Agreement (the “2021 ATM Agreement”) with Cowen and Company, LLC (“Cowen”) with respect to an at-the-market offering program under which the Company could offer and sell shares of its common stock (the “2021 ATM Shares”), having an aggregate offering price of up to $50.0 million through Cowen as its sales agent. The Company agreed to pay Cowen a commission up to 3.0% of the gross sales proceeds of such 2021 ATM Shares. As of June 30, 2022, the Company had received no proceeds from the sale of shares of common stock pursuant to the 2021 ATM Agreement.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/topic&trid=2208762

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-Based Compensation

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

10. Stock-Based Compensation

Stock Options

The Company’s 2017 Stock Option and Incentive Plan (the “2017 Stock Plan”) became effective in November 2017, upon the closing of the Company’s initial public offering and will expire in October 2027. Under the 2017 Stock Plan, the Company may grant incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units (“RSUs”) and other stock-based awards. The Company’s 2014 Stock Incentive Plan (the “2014 Stock Plan”) was terminated in November 2017 effective upon the completion of the Company’s initial public offering and no further options will be granted under the 2014 Stock Plan. At June 30, 2022, there were 598,619 options outstanding under the 2014 Stock Plan.

As of June 30, 2022, there were 6,143,876 shares of the Company’s common stock authorized for issuance under the 2017 Stock Plan, including 359,652 options that have been forfeited from the 2014 Stock Plan.

At June 30, 2022, there were 2,899,006 options available for issuance under the 2017 Stock Plan, 3,172,816 options outstanding and 42,250 RSUs outstanding. Awards granted under the 2017 Stock Plan have a term of ten years. Vesting of awards under the 2017 Stock Plan is determined by the board of directors, but is generally over one to four-year terms.

The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions:


	Six Months Ended June 30,
	2021		2022
Risk-free interest rate	0.50% - 0.88%		1.67% - 3.58%
Expected dividend yield	0%		0%
Expected life	5.5-6.7 years		5.5-6.7 years
Expected volatility	72%-74%		70%-73%
Weighted-average grant date fair value	$	4.26	$	2.97

The following table summarizes information about stock option activity during the six months ended June 30, 2022 (in thousands, except share and per share data):


	NUMBER OF SHARES			WEIGHTED- AVERAGE EXERCISE PRICE		WEIGHTED- AVERAGE REMAINING CONTRACTUAL TERM		AGGREGATE INTRINSIC VALUE
Outstanding, December 31, 2021		2,662,752		$	6.28
Granted		1,138,469			4.63
Exercised		(4,781	)		4.42
Forfeited		(25,005	)		6.58
Outstanding, June 30, 2022		3,771,435		$	5.79		7.79	$	1,097
Vested and exercisable, June 30, 2022		1,782,180		$	6.17		6.35	$	739
Vested and expected to vest, June 30, 2022		3,090,150		$	5.85		7.51	$	978

The following table summarizes information about RSU activity during the six months ended June 30, 2022:


	RSUs		AVERAGE GRANT DATE FAIR VALUE (IN DOLLARS PER SHARE)
Outstanding, December 31, 2021		42,250	$	3.25
Granted		—		—
Vested		—		—
Forfeited		—		—
RSUs outstanding at June 30, 2022		42,250	$	3.25

Unrecognized compensation expense related to unvested options as of June 30, 2022 was $4.1 million and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 2.5 years. Unrecognized compensation expense related to unvested RSUs as of June 30, 2022 was $11,000 and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 3 months.

Employee Stock Purchase Plan

In October 2017, the board of directors approved the 2017 Employee Stock Purchase Plan ("the ESPP") which became effective in November 2017, upon the closing of the Company's IPO. As part of the ESPP, eligible employees may acquire an ownership

interest in the Company by purchasing common stock, at a discount, through payroll deductions. Eligible employees who elected to participate were able to participate in the ESPP beginning September 1, 2021.

During the six months ended June 30, 2022, 23,658 shares of common stock were issued under the ESPP. As of June 30, 2022, there were 1,164,971 shares of common stock available for issuance under the ESPP.

The Company recorded stock-based compensation expense in the following expense categories of its accompanying condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2021 and 2022 (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2022		2021		2022
Research and development	$	233	$	265	$	459	$	519
General and administrative		356		415		651		797
Total	$	589	$	680	$	1,110	$	1,316

Commitments and Contingencies

6 Months Ended

Jun. 30, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

11. Commitments and Contingencies

Operating Leases

The Company leases office facilities and equipment under long-term, non-cancelable operating lease agreements. The leases expire at various dates through 2025 and do not include renewal options.

Certain leases provide for increases in future minimum annual rental payments as defined in the lease agreements. The leases generally also include real estate taxes and common area maintenance charges in the annual rental payments.

Pursuant to the terms of its lease agreement for the Company’s headquarters, the Company obtained a letter of credit in the amount of approximately $182,000 as security on the lease obligation. The letter of credit is listed as restricted cash on the Company’s consolidated balance sheets.

Short-term leases are leases having a term of twelve months or less. The Company recognizes short-term leases on a straight-line basis and does not record a related lease asset or liability for such leases.

The following is a maturity analysis of the annual undiscounted cash flows of the operating lease liabilities as of June 30, 2022 (in thousands):


Year ended:
December 31, 2022	$	286
December 31, 2023		596
December 31, 2024		9
December 31, 2025		1
Total minimum lease payments		892
Less imputed interest		(68	)
Total	$	824


	Six Months Ended June 30,
	2021			2022
Lease cost:
Operating lease cost	$	244		$	250
Short-term lease cost		-			18
Sublease income		(26	)		(26	)
Total lease cost	$	218		$	242
Other information
Cash paid for amounts included in the measurement of lease liabilities	$	262		$	264
Operating cash flows from operating leases	$	(28	)	$	(26	)
Weighted-average remaining lease term - operating leases	1.4 years			1.4 years
Weighted-average discount rate - operating leases		10.1	%		10.1	%

Research and Development Agreements

As part of the Company’s research and development efforts, the Company enters into research and development agreements with certain companies. These agreements contain varying terms and provisions which include fees and milestones to be paid by the Company. Some of these agreements also contain provisions which require the Company to make payments for exclusivity in the development of products in the area of loop diuretics.

Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2022

Accounting Policies [Abstract]

Use of Estimates

Cash Cash Equivalents and Restricted Cash

Cash, Cash Equivalents and Restricted Cash


	December 31, 2021		June 30, 2022
Cash and cash equivalents	$	74,268	$	41,178
Restricted cash		182		182
Cash, cash equivalents and restricted cash	$	74,450	$	41,360

Concentration of Credit Risk

Disclosure of accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.

+ References + Details

Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2022

Accounting Policies [Abstract]

Schedule of Cash, Cash Equivalents and Restricted Cash


	December 31, 2021		June 30, 2022
Cash and cash equivalents	$	74,268	$	41,178
Restricted cash		182		182
Cash, cash equivalents and restricted cash	$	74,450	$	41,360

Net Loss per Share (Tables)

6 Months Ended

Jun. 30, 2022

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss Per Share of Common Stock

The following table sets forth the computation of basic and diluted net loss per share of common stock (in thousands, except share and per share data):


	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2022			2021			2022
Net loss	$	(7,062	)	$	(9,697	)	$	(14,164	)	$	(17,428	)
Weighted-average shares used in computing net loss per share		27,355,454			27,378,507			27,346,141			27,373,459
Net loss per share, basic and diluted	$	(0.26	)	$	(0.35	)	$	(0.52	)	$	(0.64	)

Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2022		2021		2022
Stock options to purchase common stock		2,677,368		3,771,435		2,677,368		3,771,435
Unvested restricted stock units		42,250		42,250		42,250		42,250
Total		2,719,618		3,813,685		2,719,618		3,813,685

Investments (Tables)

6 Months Ended

Jun. 30, 2022

Investments, Debt and Equity Securities [Abstract]

Summary of Available-for-Sale Classified Investments

A summary of the Company’s available-for-sale classified investments as of December 31, 2021 and June 30, 2022 consisted of the following (in thousands):


	At December 31, 2021
Investments - Current:	Cost Basis		Accumulated Unrealized Gains		Accumulated Unrealized Losses			Fair Value
Corporate debt securities	$	1,011	$	-	$	(1	)	$	1,010
Total	$	1,011	$	-	$	(1	)	$	1,010


	At June 30, 2022
Investments - Current:	Cost Basis		Accumulated Unrealized Gains		Accumulated Unrealized Losses			Fair Value
United States Treasury securities	$	9,992	$	-	$	(6	)	$	9,986
Corporate debt securities		1,801		-		(1	)		1,800
Commercial paper		2,887		-		-			2,887
Total	$	14,680	$	-	$	(7	)	$	14,673

Summary of Amortized Cost and Fair Value of Available-for-Sale Investments by Contract Maturity

The amortized cost and fair value of the Company’s available-for-sale investments, by contract maturity, as of June 30, 2022 consisted of the following (in thousands):


	Amortized Cost		Fair Value
Due in one year or less	$	14,680	$	14,673
Total	$	14,680	$	14,673

Property and Equipment (Tables)

6 Months Ended

Jun. 30, 2022

Property, Plant and Equipment [Abstract]

Schedule of Purchased Property and Equipment

Purchased property and equipment consist of the following (dollars in thousands):


	ESTIMATED USEFUL LIFE	December 31, 2021			June 30, 2022
Office equipment	5 years	$	10		$	6
Office furniture	7 years		126			126
Computer equipment	3 years		8			8
Leasehold improvements	Life of lease		95			95
			239			235
Less: Accumulated depreciation			(170	)		(178	)
Property and equipment, net		$	69		$	57

Accrued Expenses (Tables)

6 Months Ended

Jun. 30, 2022

Accrued Liabilities, Current [Abstract]

Schedule of Accrued Expenses

Accrued expenses consist of the following (in thousands):


	December 31, 2021		June 30, 2022
Contract research and development	$	2,350	$	2,162
Employee compensation and related costs		1,152		1,412
Consulting and professional service fees		265		386
Interest		154		106
Financing related costs		60		60
State taxes		5		—
Other		9		—
Total accrued expenses	$	3,995	$	4,126

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2022

Fair Value Disclosures [Abstract]

Summary of Assets Measured at Fair Value on Recurring Basis


	As of December 31, 2021
	TOTAL		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	72,449	$	72,449	$	—	$	—
Total cash equivalents		72,449		72,449		—		—

Corporate debt securities		1,010		—		1,010		—
Investments		1,010		—		1,010		—

Total	$	73,459	$	72,449	$	1,010	$	—


	As of June 30, 2022
	TOTAL		Quoted Prices in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	$	39,381	$	38,381	$	1,000	$	—
Total cash equivalents		39,381		38,381		1,000		—

United States Treasury securities		9,986		9,986		—		—
Corporate debt securities		1,800		—		1,800		—
Commercial paper		2,887		—		2,887		—
Investments		14,673		9,986		4,687		—

Total	$	54,054	$	48,367	$	5,687	$	—

Term Loan (Tables)

6 Months Ended

Jun. 30, 2022

Debt Disclosure [Abstract]

Schedule of Total Term Loan and Unamortized Debt Discount

Total term loan and unamortized debt discount balances are as follows (in thousands):


	June 30, 2022
Face value	$	12,500
Less: discount		(186	)
Total	$	12,314
Less: current portion		(9,851	)
Long-term portion	$	2,463

Schedule of Future Principal Payments Due

As of June 30, 2022, future principal payments due under the 2019 Loan Agreement are as follows (in thousands):


Year ended:
December 31, 2022	$	5,000
December 31, 2023		7,500
Total	$	12,500

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Estimated Fair Value of Options Valuation Assumptions

The fair value of options at date of grant was estimated using the Black-Scholes option-pricing model with the following assumptions:


	Six Months Ended June 30,
	2021		2022
Risk-free interest rate	0.50% - 0.88%		1.67% - 3.58%
Expected dividend yield	0%		0%
Expected life	5.5-6.7 years		5.5-6.7 years
Expected volatility	72%-74%		70%-73%
Weighted-average grant date fair value	$	4.26	$	2.97

Summary of Information about Stock Option Activity

The following table summarizes information about stock option activity during the six months ended June 30, 2022 (in thousands, except share and per share data):


	NUMBER OF SHARES			WEIGHTED- AVERAGE EXERCISE PRICE		WEIGHTED- AVERAGE REMAINING CONTRACTUAL TERM		AGGREGATE INTRINSIC VALUE
Outstanding, December 31, 2021		2,662,752		$	6.28
Granted		1,138,469			4.63
Exercised		(4,781	)		4.42
Forfeited		(25,005	)		6.58
Outstanding, June 30, 2022		3,771,435		$	5.79		7.79	$	1,097
Vested and exercisable, June 30, 2022		1,782,180		$	6.17		6.35	$	739
Vested and expected to vest, June 30, 2022		3,090,150		$	5.85		7.51	$	978

Schedule of RSU Activity

The following table summarizes information about RSU activity during the six months ended June 30, 2022:


	RSUs		AVERAGE GRANT DATE FAIR VALUE (IN DOLLARS PER SHARE)
Outstanding, December 31, 2021		42,250	$	3.25
Granted		—		—
Vested		—		—
Forfeited		—		—
RSUs outstanding at June 30, 2022		42,250	$	3.25

Summary of Stock-Based Compensation Expense


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2022		2021		2022
Research and development	$	233	$	265	$	459	$	519
General and administrative		356		415		651		797
Total	$	589	$	680	$	1,110	$	1,316

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2022

Commitments and Contingencies Disclosure [Abstract]

Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities

The following is a maturity analysis of the annual undiscounted cash flows of the operating lease liabilities as of June 30, 2022 (in thousands):


Year ended:
December 31, 2022	$	286
December 31, 2023		596
December 31, 2024		9
December 31, 2025		1
Total minimum lease payments		892
Less imputed interest		(68	)
Total	$	824

Schedule of Lease Cost and Other Information of Operating Lease Liabilities


	Six Months Ended June 30,
	2021			2022
Lease cost:
Operating lease cost	$	244		$	250
Short-term lease cost		-			18
Sublease income		(26	)		(26	)
Total lease cost	$	218		$	242
Other information
Cash paid for amounts included in the measurement of lease liabilities	$	262		$	264
Operating cash flows from operating leases	$	(28	)	$	(26	)
Weighted-average remaining lease term - operating leases	1.4 years			1.4 years
Weighted-average discount rate - operating leases		10.1	%		10.1	%

Description of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (207,126)	$ (189,698)
Cash, cash equivalents, restricted cash, and short-term investments	$ 56,000

Significant Accounting Policies - Additional Information (Details)	6 Months Ended
	Jun. 30, 2022 USD ($)
Schedule Of Accounting Policies [Line Items]
Restricted cash	$ 182,000
Potential interest and penalties associated with uncertain tax positions, accruals	$ 0
Amortized period for expenses incurred for research and development in united states	5 years
Amortized period for expenses incurred for research and development outside united states	15 years
Letter of Credit
Schedule Of Accounting Policies [Line Items]
Restricted cash	$ 182,000

Significant Accounting Policies - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 41,178	$ 74,268
Restricted cash		182
Restricted cash	182
Cash, cash equivalents and restricted cash	$ 41,360	$ 74,450	$ 75,151	$ 72,001

Net Loss per Share - Computation of Basic and Diluted Net Loss Per Share of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net loss	$ (9,697)	$ (7,062)	$ (17,428)	$ (14,164)
Weighted-average shares used in computing net loss per share, basic	27,378,507	27,355,454	27,373,459	27,346,141
Weighted-average shares used in computing net loss per share, diluted	27,378,507	27,355,454	27,373,459	27,346,141
Net loss per share, basic	$ (0.35)	$ (0.26)	$ (0.64)	$ (0.52)
Net loss per share, diluted	$ (0.35)	$ (0.26)	$ (0.64)	$ (0.52)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 7
-URI https://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126968391&loc=SL7669625-108580

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
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-Section S99
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-Subparagraph (SX 210.13-01(a)(5))
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Reference 32: http://www.xbrl.org/2003/role/disclosureRef
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Reference 33: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 34: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,813,685	2,719,618	3,813,685	2,719,618
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,771,435	2,677,368	3,771,435	2,677,368
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	42,250	42,250	42,250	42,250

Investments - Summary of Available-for-Sale Classified Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Marketable Securities [Line Items]
Cost Basis	$ 14,680	$ 1,011
Accumulated Unrealized Losses	(7)	(1)
Fair Value	14,673	1,010
United States Treasury Securities
Marketable Securities [Line Items]
Cost Basis	9,992
Accumulated Unrealized Losses	(6)
Fair Value	9,986
Corporate Debt Securities
Marketable Securities [Line Items]
Cost Basis	1,801	1,011
Accumulated Unrealized Losses	(1)	(1)
Fair Value	1,800	$ 1,010
Commercial Paper
Marketable Securities [Line Items]
Cost Basis	2,887
Fair Value	$ 2,887

Investments - Summary of Amortized Cost and Fair Value of Available-for-Sale Investments by Contract Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 14,680
Amortized Cost, Total	14,680	$ 1,011
Fair Value, Due in one year or less	14,673
Fair Value, Total	$ 14,673	$ 1,010

Property and Equipment - Schedule of Purchased Property and Equipment (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 235	$ 239
Less: Accumulated depreciation	(178)	(170)
Property and equipment, net	$ 57	69
Office Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	5 years
Property and equipment, gross	$ 6	10
Office Furniture
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	7 years
Property and equipment, gross	$ 126	126
Computer Equipment
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	3 years
Property and equipment, gross	$ 8	8
Leasehold Improvements
Property Plant And Equipment [Line Items]
ESTIMATED USEFUL LIFE	Life of lease
Property and equipment, gross	$ 95	$ 95

Property and Equipment - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 9,000	$ 8,000	$ 18,000	$ 16,000

Accrued Expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Contract research and development	$ 2,162	$ 2,350
Employee compensation and related costs	1,412	1,152
Consulting and professional service fees	386	265
Interest	106	154
Financing related costs	60	60
State taxes		5
Other		9
Total accrued expenses	$ 4,126	$ 3,995

Fair Value of Financial Instruments - Summary of Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Assets:
Cash equivalents	$ 39,381	$ 72,449
Investments	14,673	1,010
Total	54,054	73,459
United States Treasury Securities
Assets:
Investments	9,986
Corporate Debt Securities
Assets:
Investments	1,800	1,010
Commercial Paper
Assets:
Investments	2,887
Quoted Prices in Active Markets (Level 1) [Member]
Assets:
Cash equivalents	38,381	72,449
Investments	9,986
Total	48,367	72,449
Quoted Prices in Active Markets (Level 1) [Member] \| United States Treasury Securities
Assets:
Investments	9,986
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Cash equivalents	1,000
Investments	4,687	1,010
Total	5,687	1,010
Significant Other Observable Inputs (Level 2) [Member] \| Corporate Debt Securities
Assets:
Investments	1,800	$ 1,010
Significant Other Observable Inputs (Level 2) [Member] \| Commercial Paper
Assets:
Investments	$ 2,887

Term Loan - Additional Information (Details) - SLR Investment Corp. and Silicon Valley Bank - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	May 31, 2017
2017 Loan Agreement
Debt Instrument [Line Items]
Unpaid borrowings						$ 10,000,000.0
2019 Loan Agreement
Debt Instrument [Line Items]
Loan agreement, maturity date	Sep. 17, 2023
Debt instrument, interest rate terms				The interest rate under the 2019 Loan Agreement is the higher of (i) LIBOR plus 7.95% or (ii) 10.18%
Debt instrument, effective interest rate		10.18%		10.18%
Exit fee, percentage				4.00%
Exit fee				$ 800,000
Unpaid borrowings	$ 20,000,000.0	$ 12,500,000		12,500,000
Amortization of debt discount		74,000	$ 95,000	$ 155,000	$ 182,000
Prepayment premium percentage after year two				0.50%
Final payment fee				$ 500,000
Amortization of final payment fee		$ 29,000	$ 41,000	$ 63,000	$ 81,000
Increase in interest rate on default				5.00%
2019 Loan Agreement \| Minimum
Debt Instrument [Line Items]
Interest rate, minimum		10.18%		10.18%
Prepayment premium percentage two				0.01
2019 Loan Agreement \| Maximum
Debt Instrument [Line Items]
Prepayment premium percentage one				0.03
2019 Loan Agreement \| Libor
Debt Instrument [Line Items]
Basis spread on variable base rate				7.95%

Term Loan - Schedule of Total Term Loan and Unamortized Debt Discount (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2019
Debt Instrument [Line Items]
Less: current portion	$ (9,851)	$ (9,805)
Long-term portion	2,463	$ 7,354
2019 Loan Agreement \| SLR Investment Corp. and Silicon Valley Bank
Debt Instrument [Line Items]
Loan and security agreement, amount	12,500		$ 20,000
Less: discount	(186)
Total	12,314
Less: current portion	(9,851)
Long-term portion	$ 2,463

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Term Loan - Schedule of Future Principal Payments Due (Details) - 2019 Loan Agreement - SLR Investment Corp. and Silicon Valley Bank - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2019
Debt Instrument [Line Items]
December 31, 2022	$ 5,000
December 31, 2023	7,500
Total	$ 12,500	$ 20,000

Stockholders' Equity - Additional Information (Details) - 2021 ATM Agreement - Cowen - Common Stock - USD ($)		6 Months Ended
	Mar. 23, 2021	Jun. 30, 2022
Stockholders Equity Note [Line Items]
Proceeds from sale of shares,Net		$ 0
Maximum
Stockholders Equity Note [Line Items]
Aggregate offering price	$ 50,000,000.0
Percentage of commission on gross sales proceeds	3.00%

Stock-Based Compensation - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional options granted	1,138,469
Stock option, number of shares outstanding	3,771,435	2,662,752
Unrecognized compensation expense	$ 4,100,000
Recognition period (in years)	2 years 6 months
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense	$ 11,000
Recognition period (in years)	3 months
2017 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option and incentive plan effective date	Nov. 30, 2017
Stock option and incentive plan expiration date	Oct. 31, 2027
Stock option, number of shares outstanding	3,172,816
Number of common shares authorized for issuance	6,143,876
Stock options, available for issuance	2,899,006
Term of option granted	10 years
2017 Stock Plan \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term	1 year
2017 Stock Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting term	4 years
2017 Stock Plan \| Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of restricted stock units outstanding	42,250
2014 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional options granted	0
Stock option and incentive plan expiration date	Nov. 30, 2017
Stock option, number of shares outstanding	598,619
Number of options forfeited	359,652
2017 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock shares issued	23,658
Number of common stock shares available for issuance	1,164,971

Stock-Based Compensation - Schedule of Estimated Fair Value of Options Valuation Assumptions (Details) - $ / shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate, minimum	1.67%	0.50%
Risk-free interest rate, maximum	3.58%	0.88%
Expected dividend yield	0.00%	0.00%
Expected volatility, minimum	70.00%	72.00%
Expected volatility, maximum	73.00%	74.00%
Weighted-average grant date fair value	$ 2.97	$ 4.26
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	5 years 6 months	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life	6 years 8 months 12 days	6 years 8 months 12 days

Stock-Based Compensation - Summary of Information about Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($) $ / shares shares
NUMBER OF SHARES
Number of shares outstanding, beginning balance \| shares	2,662,752
Additional options granted \| shares	1,138,469
Number of shares exercised \| shares	(4,781)
Number of shares forfeited \| shares	(25,005)
Number of shares outstanding, ending balance \| shares	3,771,435
Vested and exercisable, ending balance \| shares	1,782,180
Vested and expected to vest, ending balance \| shares	3,090,150
WEIGHTED-AVERAGE EXERCISE PRICE
Weighted average exercise prices, outstanding beginning balance \| $ / shares	$ 6.28
Weighted average exercise prices, granted \| $ / shares	4.63
Weighted average exercise prices, exercised \| $ / shares	4.42
Weighted average exercise prices, forfeited \| $ / shares	6.58
Weighted average exercise prices, outstanding ending balance \| $ / shares	5.79
Weighted average exercise prices, vested and exercisable ending balance \| $ / shares	6.17
Weighted average exercise prices, vested and expected to vest ending balance \| $ / shares	$ 5.85
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM
Weighted average remaining contractual term, outstanding	7 years 9 months 14 days
Weighted average remaining contractual term, vested and exercisable	6 years 4 months 6 days
Weighted average remaining contractual term, vested and expected to vest	7 years 6 months 3 days
AGGREGATE INTRINSIC VALUE
Aggregate intrinsic value, outstanding ending balance \| $	$ 1,097
Aggregate intrinsic value, vested and exercisable ending balance \| $	739
Aggregate intrinsic value, vested and expected to vest ending balance \| $	$ 978

Stock-Based Compensation - Schedule of RSU Activity (Details) - Restricted Stock Units (RSUs)	6 Months Ended
	Jun. 30, 2022 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs Outstanding, December 31, 2021 \| shares	42,250
RSUs Granted \| shares	0
RSUs Vested \| shares	0
RSUs Forfeited \| shares	0
RSUs outstanding at March 31, 2022 \| shares	42,250
AVERAGE GRANT DATE FAIR VALUE, Outstanding, December 31, 2021 \| $ / shares	$ 3.25
AVERAGE GRANT DATE FAIR VALUE, Granted \| $ / shares	0
AVERAGE GRANT DATE FAIR VALUE, Vested \| $ / shares	0
AVERAGE GRANT DATE FAIR VALUE, Forfeited \| $ / shares	0
AVERAGE GRANT DATE FAIR VALUE, RSUs outstanding at March 31, 2022 \| $ / shares	$ 3.25

Stock-Based Compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 680	$ 589	$ 1,316	$ 1,110
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	265	233	519	459
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 415	$ 356	$ 797	$ 651

Commitments and Contingencies - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Commitments And Contingencies [Line Items]
Operating leases expire	2025
Restricted cash	$ 182,000
Short-term lease asset	785,000	$ 410,000
Short-term lease liability	553,000	$ 476,000
Short-term Leases Recognized on Straight-line Basis
Commitments And Contingencies [Line Items]
Short-term lease asset	0
Short-term lease liability	0
Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash	182,000
Letter of Credit \| Lease Agreement Require Standby Letter of Credit
Commitments And Contingencies [Line Items]
Restricted cash	$ 182,000

Commitments and Contingencies - Schedule of Maturity Analysis of Annual Undiscounted Cash Flows of Operating Lease Liabilities (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Year ended:
December 31, 2022	$ 286
December 31, 2023	596
December 31, 2024	9
December 31, 2025	1
Total minimum lease payments	892
Less imputed interest	(68)
Total	$ 824

Commitments and Contingencies - Schedule of Lease Cost and Other Information of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Lease cost:
Operating lease cost	$ 250	$ 244
Short-term lease cost	18
Sublease income	(26)	(26)
Total lease cost	242	218
Other information
Cash paid for amounts included in the measurement of lease liabilities	264	262
Operating cash flows from operating leases	$ (26)	$ (28)
Weighted-average remaining lease term - operating leases	1 year 4 months 24 days	1 year 4 months 24 days
Weighted-average discount rate - operating leases	10.10%	10.10%

Stock-Based Compensation - Schedule of RSU Activity (Details) - Restricted Stock Units (RSUs)	6 Months Ended
	Jun. 30, 2022 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs Outstanding, December 31, 2021 \| shares	42,250
RSUs Granted \| shares	0
RSUs Vested \| shares	0
RSUs Forfeited \| shares	0
RSUs outstanding at March 31, 2022 \| shares	42,250
AVERAGE GRANT DATE FAIR VALUE, Outstanding, December 31, 2021 \| $ / shares	$ 3.25
AVERAGE GRANT DATE FAIR VALUE, Granted \| $ / shares	0
AVERAGE GRANT DATE FAIR VALUE, Vested \| $ / shares	0
AVERAGE GRANT DATE FAIR VALUE, Forfeited \| $ / shares	0
AVERAGE GRANT DATE FAIR VALUE, RSUs outstanding at March 31, 2022 \| $ / shares	$ 3.25