Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Summary of Stock-based Awards Activity Under the 2008 Plan, 2015 Plan and Inducement Plan

The following table provides a summary of stock-based awards activity for the six months ended June 30, 2022:

Stock Options:

Outstanding at December 31, 2021	6,218,841
Granted	95,000
Exercised	—
Expired/cancelled/forfeited	(249,563	)
Outstanding at June 30, 2022	6,064,278

The total compensation cost related to non-vested stock options not yet recognized as of June 30, 2022 was $2.7 million, which will be recognized over a weighted-average period of approximately 2.5 years.

RSUs:

Outstanding at December 31, 2021	1,272,375
Granted	—
Vested	(5,500	)
Forfeited	(125,000	)
Outstanding at June 30, 2022	1,141,875

Stock-based Compensation Expense included in Accompanying Statements of Operations and Comprehensive Loss

Stock-based compensation expense is included in the following line items in the accompanying statements of operations and comprehensive loss for the three and six months ended June 30, 2022 and 2021 (in thousands):

	Three months ended June 30,				Six months ended June 30,
	2022		2021		2022		2021
Research and development	$	71	$	291	$	247	$	755
General and administrative		385		480		783		962
Total stock-based compensation	$	456	$	771	$	1,030	$	1,717