Stock-based compensation expense, which includes expense for both employees and non-employees, has been reported in the Company’s condensed statements of operations for the three and nine months ended September 30, 2019 and 2018 as follows (in thousands):

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2019		2018		2019		2018
Research and development	$	146	$	24	$	430	$	394
General and administrative		759		659		2,101		1,203
Total stock-based compensation	$	905	$	683	$	2,531	$	1,597

The following table summarizes the Company’s stock option activity under the Company’s 2013 Equity Incentive Plan and the Company’s 2018 Equity Incentive Plan for the nine months ended September 30, 2019:

						Weighted average
				Weighted average		remaining contractual		Aggregate intrinsic
	Number of shares			exercise price		life (in years)		value
Outstanding as of December 31, 2018		1,529,883		$	8.03
Granted		647,575			10.74
Exercised		(40,041	)		5.49
Forfeitures		(151,216	)		8.87
Outstanding as of September 30, 2019		1,986,201		$	8.90		8.7	$	11,771,966
Options vested and exercisable as of September 30, 2019		584,780		$	7.29		8.3	$	4,403,891

As of September 30, 2019, the total unrecognized compensation related to unvested stock option awards granted was $9.3 million, which the Company expects to recognize over a weighted-average period of 2.8 years.

Pursuant to an Amended and Restated Stock Purchase Agreement (the “Amended and Restated Agreement”) between the Company and the former Chief Scientific Officer (“CSO”), 848,859 shares held by the former CSO are subject to repurchase at $0.0001 per share in the event the CSO ceases to be a consultant. These shares will be released from the repurchase option on the earliest to occur of (i) a change in control, (ii) regulatory approval of the Company’s new drug application for cantharidin, (iii) commercial sale of products and (iv) a covered termination, as defined in the Amended and Restated Agreement.

As of September 30, 2019, the total unrecognized compensation expense related to the nonvested shares was $0.3 million. No compensation expense has been recognized for these nonvested shares as these shares are performance-based and the triggering event was not determined to be probable as of September 30, 2019. There was no activity related to restricted stock during the nine months ended September 30, 2019.