On July 1, 2020, the Company’s board of directors approved the 2020 Equity Incentive Plan (“Existing Plan”) which permits the granting of incentive stock options, non-statutory stock options, stock appreciation rights, RSAs, RSUs and other stock-based awards to employees, directors, officers and consultants. On September 16, 2020, the approval date of the New Plan (as defined below), no additional awards will be granted under the Existing Plan. The terms of the Existing Plan will continue to govern the terms of outstanding equity awards that were granted prior to approval of the New Plan.

On September 16, 2020, the Company’s stockholders approved the 2020 Stock Incentive Plan (“New Plan”), which became effective upon the execution of the underwriting agreement in connection with the IPO. The number of shares of common stock reserved for issuance under the New Plan automatically increases on January 1 of each year, for a period of ten years, from January 1, 2021 continuing through January 1, 2030, by 5% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors. On January 1, 2023, the Company’s board of directors increased the number of shares of common stock reserved for issuance under the New Plan by 3,160,375 shares.

Furthermore, on September 16, 2020, the Company’s stockholders approved the Employee Stock Purchase Plan (“ESPP”), which became effective upon the execution of the underwriting agreement in connection with the IPO. The maximum number of shares of common stock that may be issued under the ESPP will not exceed 362,000 shares of common stock, plus the number of shares of common stock that are automatically added on January 1 of each year for a period of up to ten years, commencing on the first January 1 following the IPO and ending on (and including) January 1, 2030, in an amount equal to the lesser of (i) 1.0% of the total number of shares of capital stock outstanding on December 31 of the preceding calendar year, and (ii) 724,000 shares of common stock. No shares were added to the

ESPP in 2021. On January 1, 2022 and 2023, the Company’s board of directors increased the number of shares of common stock reserved for issuance under the ESPP by 384,739 and 632,075 respectively. The Company has issued 73,073 shares of common stock under the ESPP as of December 31, 2022.

The number of shares available for grant under the Company's incentive plans were as follows:


	Existing			New
	Plan			Plan			Total
Available for grant - January 1, 2021		—			2,941,509			2,941,509
Plan adjustments and amendments		(250,778	)		1,685,712			1,434,934
Grants		—			(3,192,600	)		(3,192,600	)
Forfeitures		250,778			217,480			468,258
Available for grant - December 31, 2021		—			1,652,101			1,652,101
Plan adjustments and amendments		—			1,923,697			1,923,697
Grants		—			(4,775,676	)		(4,775,676	)
Forfeitures		—			2,267,560			2,267,560
Available for grant - December 31, 2022		—			1,067,682			1,067,682

On July 1, 2020, options to purchase 2,896,782 shares of common stock under the Existing Plan were awarded to certain employees and consultants of the Company with an exercise price per share of $0.80, which were expected to vest over a four-year period, all of which were subsequently cancelled (the “Cancelled Options”). The grant date fair value of the Cancelled Options was $13.8 million at the original grant date. In exchange, the Company awarded 2,518,932 RSUs on September 2, 2020, which are expected to vest over a four-year term. The Company accounted for the changes in award terms as a modification in accordance with ASC 718 Compensation – Stock Compensation. The modification was accounted for as an exchange of the original award for a new award with total compensation cost equal to the grant-date fair value of the original award plus any incremental value measured on the modification date. The Company determined that there was no incremental value as the fair value of the original award immediately before the modification was greater than the fair value of the new award immediately after the modification. Accordingly, the Company continues to recognize the remaining compensation cost of the Cancelled Options over the vesting period of the RSUs.

During the year ended December 31, 2022, options to purchase 4,775,676 shares of common stock under the New Plan were awarded with a weighted-average grant date fair value per share of $3.07. The stock options vest over one to four years and have a ten-year contractual term.

The following weighted-average assumptions were used to estimate the fair value of stock options granted during the years ended December 31, 2022 and 2021:


	Year Ended December 31,
	2022			2021
Risk-free interest rate		2.95	%		0.84	%
Expected dividend yield		—			—
Expected term (in years)		6.1			6.0
Expected volatility		78	%		75	%

The following table summarizes stock option activity during the years ended December 31, 2022 and 2021:


						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Stock			Exercise		Contractual		Value
	Options			Price		Life (in years)		(in thousands)
Outstanding at January 1, 2021		674,842		$	20.68		9.8	$	3,953
Options granted		3,192,600			24.99		—		—
Options cancelled or forfeited		(217,480	)		26.07		—		—
Outstanding at December 31, 2021		3,649,962		$	24.13		9.2	$	—
Options granted		4,775,676			4.48		—		—
Options cancelled or forfeited		(2,048,192	)		15.25		—		—
Options expired		(219,368	)		24.36		—		—
Outstanding at December 31, 2022		6,158,078		$	11.84		8.9	$	62
Options exercisable at December 31, 2022		1,225,613		$	24.88		7.3	$	—

The aggregate intrinsic value in the above table is calculated as the difference between the fair value of the Company’s common stock as of December 31, 2022 and the exercise price of the stock options. As of December 31, 2022, the total unrecognized compensation related to unvested stock option awards granted was $26.4 million, which the Company expects to recognize over a weighted-average period of approximately 2.5 years. No stock options were exercised during the period.

On September 2, 2020, the Company issued 331,121 RSUs to an employee under the Existing Plan; 25% of the shares of common stock underlying the RSUs vest at each anniversary over a four-year period. The RSUs are subject to a service-based vesting condition. The Company at any time may accelerate the vesting of the RSUs. Such shares are not accounted for as outstanding until they vest. As of December 31, 2022, the total unrecognized compensation related to unvested RSUs granted, including the remaining compensation cost associated with the RSUs granted on September 2, 2020 in exchange for the Cancelled Options, was $6.4 million which is expected to be amortized on a straight-line basis over a weighted-average period of approximately 1.5 years.

The Company's default tax withholding method for RSUs is the sell-to-cover method, in which shares with a market value equivalent to the tax withholding obligation are sold on behalf of the holder of the RSUs upon vesting and settlement to cover the tax withholding liability and the cash proceeds from such sales are remitted by the Company to taxing authorities.

The Company’s RSU activity for the year ended December 31, 2022 and 2021 was as follows:


				Weighted
				Average
				Grant Date
	Number			Fair Value
	of Shares			per Share
Nonvested at January 1, 2021		2,850,053		$	6.37
Restricted units granted		—			—
Vested		(712,510	)		6.37
Cancelled or forfeited		(250,778	)		5.25
Nonvested at December 31, 2021		1,886,765		$	6.52
Restricted units granted		—			—
Vested		(628,921	)		6.52
Cancelled or forfeited		—			—
Nonvested at December 31, 2022		1,257,844		$	6.52

RA Session II, the Company’s former President and Chief Executive Officer, was awarded 769,058 RSAs under the Existing Plan on July 1, 2020, which are expected to vest over a three-year term, subject to continuous employment. As of December 31, 2022, the total unrecognized compensation related to unvested RSAs granted was $0.4 million which is expected to be amortized on a straight-line basis over a weighted average period of approximately 0.2 years. The fair value of these RSAs at the grant date of July 1, 2020 was $5.28 per share.

The Company’s RSA activity for the year ended December 31, 2022 and 2021 was as follows:


				Weighted
				Average
				Grant Date
	Number			Fair Value
	of Shares			per Share
Nonvested at January 1, 2021		769,058		$	5.28
Restricted stock granted		—			—
Vested		(427,083	)		5.28
Nonvested at December 31, 2021		341,975		$	5.28
Restricted stock granted		—			—
Vested		(256,481	)		5.28
Nonvested at December 31, 2022		85,494		$	5.28

In February 2022, the Company’s board of directors authorized the first offering under the ESPP. Under the ESPP, eligible employees may purchase shares of Taysha common stock through payroll deductions at a price equal to 85% of the lower of the fair market values of the stock as of the beginning or the end of six-month offering periods. An employee’s payroll deductions under the ESPP are limited to 15% of the employee’s compensation and employees may not purchase more than 1,800 of shares of Taysha common stock during any offering period. During the year ended December 31, 2022, stock-based compensation expense related to the ESPP was not material.

During the year ended December 31, 2022, $0.2 million of stock-based compensation expense was capitalized as part of construction in progress (see Note 3). The following table summarizes the total remaining stock-based compensation expense for the stock options, RSAs and RSUs recorded in the consolidated statements of operations for the years ended December 31, 2022 and 2021 (in thousands):