Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-Based Compensation Expense

The amounts included in the consolidated statements of operations relating to stock-based compensation associated with the two equity incentive plans, performance cash awards, and Helio founders’ shares are as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development expenses	$	640,017	$	1,180,305	$	1,485,683	$	2,373,172
General and administrative expenses		654,318		1,143,256	$	1,745,230	$	2,332,046
Total stock-based compensation expense	$	1,294,335	$	2,323,561	$	3,230,913	$	4,705,218

Summary of Activity Relating to Stock Options

The table below summarizes activity relating to stock options under the incentive plans for the six months ended June 30, 2022:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value(a)
Outstanding at December 31, 2021		4,622,870		$	6.73
Granted		1,721,297		$	4.04
Forfeitures		(479,829	)	$	6.19
Outstanding at June 30, 2022		5,864,338		$	5.99		7.06	$	1,600,420
Exercisable at June 30, 2022		3,661,884		$	6.18		5.75	$	1,190,252

Summary of Activity Relating to Restricted Stock Units

The table below summarizes activity relating to restricted stock units (RSUs) for the six months ended June 30, 2022:

	Number of Shares
Outstanding at December 31, 2021		501,255
Granted		407,717
Cancelled / Forfeited		(169,586	)
Vested / Settled		(202,526	)
Outstanding at June 30, 2022		536,860

Summary of Employee Stock Purchase Plan Activity

A summary of the weighted-average grant-date fair value, and total stock-based compensation expense recognized related to the 2016 ESPP are as follows:

	Six Months Ended June 30,
	2022		2021
Weighted-average grant-date fair value per share	$	1.65	$	2.49
Total stock-based compensation expense	$	33,342	$	23,127