In 2016, the Company adopted the 2016 Stock Plan. On July 8, 2020, the Company’s stockholders approved the 2020 Stock Option and Incentive Plan (the “2020 Stock Plan”), which became effective on the date immediately prior to the effectiveness of the Company’s registration statement on Form S-1 for its IPO. The 2020 Stock Plan provides for the issuance of up to 8,376,080 of share-based awards. Subsequent to July 20, 2020, no further awards will be made under the 2016 Stock Plan and all future equity-based awards will be granted under the 2020 Stock Plan. To the extent outstanding options granted under the 2016 Plan are cancelled, forfeited or otherwise terminated without being exercised and would otherwise have been returned to the share reserve under the 2016 Plan, the number of shares underlying such awards will be available for future grant under the 2020 Stock Plan. All of the Company’s employees, officers, directors and consultants are eligible to be granted options, restricted stock units and other stock-based awards under the terms of the 2020 Stock Plan. There were 8,026,772 share-based awards available for grant at December 31, 2020.

The following table summarizes the stock option activity under the 2016 Stock Plan and the 2020 Stock Plan for the year ended December 31, 2020:

	Number of Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Term (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2019		5,306,176		$	4.62		8.99	$	3,214
Granted		2,898,663			10.90
Exercised		(297,000	)		4.09
Cancelled		(210,781	)		4.91
Outstanding at December 31, 2020		7,697,058		$	6.99		8.50	$	266,050
Vested at December 31, 2020		2,148,119		$	4.49		7.90	$	79,625
Non-vested at December 31, 2020		5,548,939		$	7.96		8.74	$	186,425

In the first quarter of 2020, the Company’s board of directors approved the issuance of options with performance-based vesting conditions to purchase 1,960,547 shares of common stock. The commencement of vesting was based on the achievement of certain scientific and operational milestones during a two-year period, for which the achievement was discretionary and subject to the approval of the Company’s board of directors. Accordingly, the Company applied variable accounting for these awards until the board of directors approved the commencement of vesting for the options. The service inception date preceded the grant date for these awards as the awards were authorized prior to the grant date, the recipients were providing service prior to the grant date and there were performance conditions that, if not met by the accounting grant date, would have resulted in the forfeiture of the award. The stock-based compensation expense for the options was determined based on the fair value of the awards on the accounting grant date. The Company’s board of directors, in its discretion, determined that a portion of the performance conditions were achieved during the second quarter of 2020 and that the remaining portion of the performance conditions were achieved during the fourth quarter of 2020. The grant dates for all performance-based awards was therefore known as of December 31, 2020, and all performance conditions have been resolved. The Company recognized stock-based compensation expense associated with the awards with performance-based vesting conditions in the amount of $25,527 in the statement of operations for the year ended December 31, 2020. Expense for these awards is recognized using an accelerated attribution model, over the four-year vesting term, commencing upon grant date.

The Company estimated the fair value of its stock options using the following assumptions:

	Year Ended December 31,
	2020			2019
Risk-free interest rate	0.4 - 1.8%			1.5 – 2.5%
Expected term (in years)		6.3			6.3
Expected volatility	73.5 - 77.6%			72.8 – 73.47%
Expected dividend yield		0	%		0	%

The weighted average grant date fair value of stock options granted during the years ended December 31, 2020 and 2019 was $30.14 per share and $3.34 per share, respectively.

Stock-based compensation expense included in the Company’s consolidated statements of operations and comprehensive loss is as follows:

	Year Ended December 31,
	2020		2019
Research and development expenses	$	14,691	$	2,687
General and administrative expenses		17,269		1,769
	$	31,960	$	4,456

As of December 31, 2020, total unrecognized compensation cost related to the unvested stock-based awards was $69,948, which is expected to be recognized over a weighted average period of 2.61 years.