6.	Stock-Based Compensation

2015

Equity Plan

The

2015

Equity Plan provides for increases to the number of shares reserved for issuance thereunder each

January 1

equal to

4.0%

of the total shares of the Company's common stock outstanding as of the immediately preceding

December 31,

unless a lesser amount is stipulated by the Compensation Committee of the Company's board of directors. Accordingly,

2,560,618

shares were added to the reserve as of

January 1, 2021,

which shares

may

be issued in connection with the grant of stock-based awards, including stock options, restricted stock, restricted stock units, stock appreciation rights and other types of awards as deemed appropriate, in each case, in accordance with the terms of the

2015

Equity Plan. As of

March 31, 2021,

there were

1,229,005

available for future issuance under the

2015

Equity Plan.

The Company recorded stock-based compensation expense in the following expense categories of its unaudited interim consolidated statements of operations for the periods indicated:

	Three Months Ended March 31,
	2021		2020
Research and development	$	33,000	$	96,530
General and administrative		148,280		94,850
Total stock-based compensation expense	$	181,280	$	191,380

The following table summarizes the activity related to all stock option grants for the

three

months ended

March

31,

2021:

	Number of Options		Weighted average exercise price per share		Weighted average remaining contractual life (in years)		Aggregate intrinsic value
Balance at January 1, 2021		2,240,204	$	8.28
Granted		876,615		1.11
Outstanding at March 31, 2021		3,116,819	$	6.26		9.01	$	475,258
Exercisable at March 31, 2021		1,363,373	$	13.10		8.25	$	331,618
Vested and expected to vest at March 31, 2021		3,116,819	$	6.26		9.01	$	475,258

The weighted average grant date fair value of stock option awards granted was

$1.06

during the

three

months ended

March 31, 2021.

The total fair value of options vested during the

three

months ended

March 31, 2021

and

2020

was

$0.2

million and

$0.2

million, respectively.

options were exercised during any of the periods presented. At

March

31,

2021,

there was

$1.4

million of unrecognized compensation expense that will be recognized over a weighted-average period of

2.29

years. During the

three

months ended

March 31, 2021,

the Company granted

385,267

performance-based stock options with an exercise price of

$1.11

per share, subject to vesting based on the satisfaction of specified performance criteria. Compensation expense for the performance-based awards is recorded over the estimated service period for each milestone when the performance conditions are deemed probable of achievement. The Company recorded stock-based compensation expense of approximately

$27,000

during the

three

months ended

March 31, 2021,

for service-based awards and performance conditions deemed probable of achievement and/or achieved. For performance-based awards containing performance conditions which were

not

deemed probable of achievement at

March 31, 2021,

stock compensation expense was recognized.

Options granted were valued using the Black-Scholes-Merton derivative investment instrument pricing model and assumptions used to value the options granted during the

three

months ended

March 31, 2021

were as follows:

Expected term (in years)	10
Risk-free interest rate	1.4	%
Expected volatility	124.6	%
Dividend yield	—

Restricted Stock Unit Awards

During the year ended

December 31, 2020,

the Company granted

153,000

restricted stock units to various members of the board of directors of the Company. The shares begin to vest

months after the grant date,

none

of which have vested as of

March 31, 2021.

The Company recognized approximately

$5,000

in expense related to these awards during the

three

months ended

March 31, 2021.

March 31, 2021,

there was approximately

$77,000

of unrecognized compensation cost that will be recognized over a weighted average period of

2.19

years.