Investments and Fair Value Instruments (Tables)

12 Months Ended

Dec. 31, 2022

Investments And Fair Value Instruments [Abstract]

Summary of Amortized Cost and Fair Value of Investment Securities Portfolio

(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
December 31, 2022
Cash equivalents:
Money market funds	$	18,620	$	—	$	—	$	18,620
Total Assets at Fair Value	$	18,620	$	—	$	—	$	18,620

(Dollars in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Estimated Fair Value
December 31, 2021
Cash equivalents:
Money market funds	$	26,842	$	—	$	—	$	26,842
Total Assets at Fair Value	$	26,842	$	—	$	—	$	26,842

Summary of Fair Value of Investment Securities

The fair value of the investment securities at December 31, 2022 were as follows:

	Fair Value Measurements at December 31, 2022
(Dollars in thousands)	Level 1		Level 2		Level 3		Total
Assets at Fair Value
Cash equivalents:
Money market funds	$	18,620	$	—	$	—	$	18,620
Total Assets at Fair Value	$	18,620	$	—	$	—	$	18,620

The fair value of the investment securities at December 31, 2021 were as follows:

	Fair Value Measurements at December 31, 2021
(Dollars in thousands)	Level 1		Level 2		Level 3		Total
Assets at Fair Value
Cash equivalents:
Money market funds	$	26,842	$	—	$	—	$	26,842
Total Assets at Fair Value	$	26,842	$	—	$	—	$	26,842

Summary of Preferred Investment Option Liabilities Measured and Recorded on Recurring Basis using Black-Scholes Model

The preferred investment option liabilities were measured and recorded on a recurring basis using the Black-Scholes Model with the following assumptions at December 31, 2022:

	August 2022 Options			August 2022 Placement Agent Options
	December 31, 2022			December 31, 2022
Expected term (in years)		4.67			4.67
Expected volatility		106.2	%		106.2	%
Risk-free interest rate		4.0	%		4.0	%
Expected dividend yield		0	%		0	%

Summary of Changes in Fair Value and Other Adjustments of Liabilities

The following table sets forth the establishment of the Company’s Level 3 liabilities, as well as a summary of the changes in the fair value and other adjustments (in thousands):

(Dollars in thousands)	Common Stock Warrant Liability - March 2018 Purchase Agreement			Common Stock Warrant Liability - June 2019 Offering			Common Stock Warrant Liability - September 2019 Offering			Common Stock Warrant Liability - January 2021 Offering			August 2022 Options			August 2022 Placement Agent Options			Contingent Liabilities			Total
Balance as of December 31, 2021	$	7		$	170		$	223		$	2,993		$	—		$	—		$	2,070		$	5,463
Reclassification upon adoption     of ASU 2020-06		(7	)		(170	)		(223	)		(2,993	)		—			—			—			(3,393	)
Initial recognition		—			—			—			—			3,824			191			—			4,015
Change in fair value and    other adjustments		—			—			—			—			(3,057	)		(152	)		(70	)		(3,279	)
Balance as of December 31, 2022	$	—		$	—		$	—		$	—		$	767		$	39		$	2,000		$	2,806