Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2021

Equity [Abstract]

Summary of Series B Preferred Stock and Accretion of Dividends

The following tables summarize Series B convertible preferred stock and the accretion of dividend activity for the nine months ended September 30, 2021 and 2020 (in thousands):

	Nine Months Ended September 30,
	2021		2020
Series B Convertible Preferred Stock:
Balance at beginning of period	$	22,969	$	21,875
Cumulative dividends on Series B convertible preferred stock		859		818
Balance at end of period	$	23,828	$	22,693
Number of Common Shares Issuable Upon Conversion:
Number of shares at beginning of period		5,742		5,469
Cumulative dividends on Series B convertible preferred stock		215		204
Number of shares at end of period		5,957		5,673

Summary of Outstanding Warrants Issued by Company

Below is the summary of outstanding warrants issued by the Company as of September 30, 2021:

Warrant Type	Number of Shares Issuable Upon Exercise		Weighted Average Exercise Price		Issue Date	Expiration Date
April 21 Funds Warrants		275,000	$	3.50	May 5, 2020	May 5, 2023

Summary of Common Stock Reserved for Future Issuance

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance as of September 30, 2021 was as follows:

Exercise of outstanding stock options, vesting of restricted stock units ("RSU"), vesting of      performance stock units ("PSU"), and issuance of RSUs vested but not released	1,527,411
Employee Stock Purchase Plan	293,888
Shares of common stock available for grant under the 2011 Plan	943,591
Warrants to purchase common stock	275,000
Shares of common stock issuable upon conversion of Series B convertible preferred stock	7,541,449
Total	10,581,339