10.

Stock-Based Compensation

2015

Equity Plan

The

2015

Equity Incentive Plan of the Company, as amended in

July 2016,

currently allows for the issuance of up to a maximum of

33,333

shares of common stock 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,

not

including shares subject to awards assumed in connection with certain transactions. As of

December

31,

2018,

there were

1,814

shares of Common Stock available for future issuance under the

2015

Equity Incentive Plan. In addition, beginning on

January 1, 2017,

on each

January 1

through the term of the plan, up to

4.0%

of the total shares of the Company’s common stock outstanding as of

December 31

will be added to the plan reserve, unless a lesser amount is stipulated by the Compensation Committee of the Company’s Board of Directors. On

January 1, 2019,

the maximum number of shares of the

2015

Equity Incentive Plan increased by

135,049

shares, or

4.0%

of the total shares of the Company’s common stock outstanding at

December

31,

2018.

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

	Year ended December 31,
	2018		2017
Research and development	$	62,161	$	674,643
General and administrative		1,159,430		716,425
Total stock-based compensation expense	$	1,221,591	$	1,391,068

The following table summarizes the activity related to all stock option grants to employees and non-employees:

	Number of Options			Weighted average exercise price per share		Weighted average remaining contractual life (in years)		Aggregate Intrinsic Value
Balance at January 1, 2017		147,214		$	121.37
Granted		23,345			36.92
Expired		(98	)		225.00
Balance at January 1, 2018		170,461		$	109.74		7.13	$	4,746
Granted		44,005			15.37
Forfeited		(10,583	)		131.25
Expired		(147	)		256.50
Outstanding at December 31, 2018		203,736		$	88.14		6.70	$	143
Exercisable at December 31, 2018		167,585		$	101.69		6.25	$	143
Vested and expected to vest at December 31, 2018		203,736		$	88.14		6.70	$	143

Generally, the options have a

ten

(

) year contractual term and vest in equal monthly installments over

three

(

) years.

Non-employee Stock Options

Non-employee options are remeasured to fair value each period through operations using a Black-Scholes option-pricing model until the options vest. There were

options granted to non-employees during the year ended

December 31, 2018

and there were

626

stock options granted to non-employees during the year ended

December

31,

2017.

The total fair value of non-employee stock options vested during the years ended

December

31,

2018

and

2017

was approximately

$4,000

and

$90,000,

respectively. At

December

31,

2018,

there was less than

$1,000

of unrecognized compensation cost related to

219

unvested stock options and subject to re-measurement until vested. The total unrecognized compensation expense will be recognized as expense over a weighted-average period of

1.16

years.

Employee Stock Options

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

$12.63

and

$30.43

during the years ended

December

31,

2018

and

2017,

respectively. The total fair value of options vested during the years ended

December

31,

2018

and

2017

were

$1.2

million and

$1.1

million, respectively.

options were exercised during any of the periods presented. At

December

31,

2018,

there was

$0.6

million of unrecognized compensation cost related to unvested options that will be recognized as expense over a weighted-average period of

1.4

years.

The grant date fair value of employee stock options is determined using the Black-Scholes model. The following assumptions were used during the years ended

December

31,

2018

and

2017:

	2018			2017
Expected term (in years)	5.27	—	5.66	5.27	—	6.00
Risk-free interest rate	2.3%	—	2.8%	1.8%	—	2.4%
Expected volatility	113.6%	—	115.0%	109.8%	—	136.7%
Dividend yield	—	—	—	—	—	—

Restricted Stock Awards

As of

December

31,

2018,

there were

unvested shares of restricted stock. During the year ended

December

31,

2018

and

2017,

204

and

409

shares vested, respectively. The fair value as of the respective vesting dates of the restricted stock awards was

$6,000

and

$12,000

for

2018

and

2017,

respectively. There were

restricted stock awards granted in

2018

2017.