	September 30, 2020		December 31, 2019
Conversion of redeemable convertible preferred stock (as converted to common stock)		—		12,048,671
Conversion of additional authorized and unissued redeemable convertible preferred stock		—		51,506
Stock options available for future grant		2,098,174		653,136
Stock options issued and outstanding		3,269,399		1,860,646
Redeemable convertible preferred stock warrants issued and outstanding		—		220,890
Common stock warrants issued and outstanding		226,191		—
Total		5,593,764		14,834,849

A summary of stock option activity for the nine months ended September 30, 2020 is set forth below:

	Ongoing Awards
	Number of Shares Available for Grant			Number of Shares Underlying Outstanding Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding, December 31, 2019		653,136			1,860,646		$	4.05		8.53	$	5,812
Assumed as part of the Merger		2,707,144			81,370		$	8.39
Options granted		(1,517,446	)		1,713,344		$	16.06
Options exercised		—			(123,141	)	$	1.57
Options forfeited or cancelled		255,340			(262,820	)	$	4.80
Outstanding, September 30, 2020		2,098,174			3,269,399		$	10.49		7.73		11,780
Shares exercisable, September 30, 2020					1,195,101		$	4.20		4.95		9,246
Vested and expected to vest, September 30, 2020					3,269,399		$	10.49		7.73		11,780

Total stock-based compensation expense recognized was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development	$	951	$	54	$	1,125	$	191
General and administrative		2,015		337		2,491		674
Total stock-based compensation	$	2,966	$	391	$	3,616	$	865

Upon completion of the Merger with resTORbio on September 15, 2020, Former Adicet’s 2014 Share Option Plan (the “2014 Plan”), Former Adicet’s 2015 Stock Incentive Plan (the “2015 Plan”), resTORbio’s 2017 Stock Incentive Plan (the “2017 Plan”), resTORbio’s 2018 Stock Incentive Plan (the “2018 Plan”) and resTORbio’s 2018 Employee Stock Purchase Plan (the “2018 ESPP”, and, collectively with the 2014 Plan, the 2015 Plan, the 2017 Plan and the 2018 Plan, the “Plans”) were assumed by the Company. The Plans are administered by the Board of Directors or, at the discretion of the Board of Directors, by a committee of the Board of Directors. No further shares will be issued from the 2014 Plan or 2017 Plan. The exercise prices, vesting and other restrictions are determined at the discretion of the Board of Directors, or its committee if so delegated, except that the exercise price per share of stock options may not be less than 100% of the fair market value of the share of common stock on the date of grant and the term of the stock option may not be greater than ten years. Incentive stock options granted to employees and restricted stock awards granted to employees, officers, members of the Board of Directors, advisors, and consultants of the Company typically vest over four years. Non-statutory options granted to employees, officers, members of the Board of Directors, advisors, and consultants of the Company typically vest over three or four years. Shares that are expired, terminated, surrendered or canceled under the Plans without having been fully exercised will be available for future awards. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards.

In 2017, resTORbio adopted the 2017 Plan. In connection with resTORbio’s initial public offering completed in January 2018, the resTORbio Board adopted and resTORbio’s stockholders approved the 2018 Plan. The 2018 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2019, by 4% of the outstanding number of shares of resTORbio’s common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Board.

Since the date of effectiveness of the 2018 Plan, resTORbio has not and will not grant any further awards under the 2017 Plan. However, any shares of common stock subject to awards under the 2017 Plan that expire, terminate, or otherwise are surrendered, canceled, forfeited or repurchased without having been fully exercised or resulting in any common stock being issued will become available for issuance under the 2018 Plan.

As of September 30, 2020, the number of shares of common stock available for grant under the 2017 and 2018 Plan is 1,462,006. As of September 30, 2020, an aggregate of 1,326,508 shares of common stock were issuable upon the exercise of outstanding stock options under the 2017 Plan and 2018 Plans at a weighted average exercise price of $15.64 per share.

At the effective time of the Merger, each outstanding and unexercised option to purchase Former Adicet’s common stock, whether vested or unvested, pursuant to the 2015 Plan and a subset of options issued pursuant to the 2014 Plan were converted into options to purchase a number of shares of the Company’s common stock based on the Exchange Ratio. Former Adicet warrants with rights to acquire Former Adicet capital stock were converted into rights to acquire a certain number of shares of the Company’s common stock based on the Exchange Ratio, subject to the terms of and adjustments in the merger agreement.

As of September 30, 2020, the number of shares of common stock available for grant under the 2017 and 2018 Plan is 636,168. As of September 30, 2020, an aggregate of 1,677,979 shares of Former Adicet common stock were issuable upon the exercise of outstanding stock options under the 2015 plan at a weighted average exercise price of $6.14 per share and an aggregate of 69,014 shares of Former Adicet common stock were issuable upon the exercise of outstanding stock options under the 2014 Plan at a weighted average exercise price of $1.27 per share.

Since the date of effectiveness of the Merger, the Company has not and will not grant any further awards under the 2014 Plan.

The resTORbio Board adopted and resTORbio’s stockholders approved the 2018 ESPP, which became effective on the date immediately preceding the date on which resTORbio’s registration statement of Form S-1 became effective. The

2018 ESPP enables eligible employees to purchase shares of resTORbio’s common stock at a discount. The number of shares of common stock originally reserved for issuance under the 2018 ESPP were 39,290 shares. The 2018 ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2019 and increasing each January 1 thereafter through January 1, 2028, by the least of (i) 1% of the outstanding number of shares of resTORbio’s common stock on the immediately preceding December 31; (ii) 77,703 shares or (iii) such number of shares as determined by the ESPP administrator. On January 1, 2019, as a result of the foregoing evergreen provision, the number of shares of common stock available for issuance under the 2018 ESPP automatically increased from 39,290 to 79,369 shares. On January 1, 2020, as a result of the foregoing evergreen provision, the number of shares of common stock available for issuance under the 2018 ESPP automatically increased from 79,369 to 131,432 shares. No shares have been issued under the 2018 ESPP during the three and six months ended June 30, 2020.

As of September 30, 2020, an aggregate of 195,898 shares of were issuable upon the exercise of inducement grants of stock options approved by the Company in accordance with Nasdaq listing Rule 5635(c)(4) at a weighted average exercise price of $16.11 per share.

In connection with the Merger, the stock options granted to Dr. Singhal were modified (refer to Note 3 for details), which resulted in acceleration and recognition of the stock compensation expense of $0.6 million during the quarter ended September 30, 2020. The modification also resulted in incremental stock compensation expense of $0.1 million that will be recognized through May 7, 2021 as the Company determined that Dr. Singhal will be providing substantial services under the Independent Contractor Agreement with Dr. Singhal through that date.

On July 14, 2020, the Company’s Board of Directors confirmed that the conditions for Dr. Singhal’s Second Target Milestone Option (as defined in Dr. Singhal’s employment agreement with the Company) had been fulfilled as the Company achieved the milestone for the selection of a clinical candidate to the second collaboration target under the Regeneron Agreement. Following the Merger, on September 17, 2020, the Company’s Board of Directors granted an option to purchase 16,931 shares of the Company’s common stock at an exercise price of $16.11 per share, (i) one-third of the shares vesting on the first anniversary of May 6, 2019, (ii) one-third of the shares vesting in 12 equal monthly installments following such first anniversary, and (iii) one-third of the shares vesting in accordance with the terms of his Transition Agreement. The Company recognized $0.1 million in stock compensation expense associated with this reward during the three months ended September 30, 2020.