As of June 30, 2023, the Company had three stock-based employee compensation plans: the Amended and Restated Stock Incentive Plan (“Incentive Plan”), the Amended and Restated Inducement Equity Incentive Plan (“Inducement Plan”) and the Amended and Restated Employee Stock Purchase Plan (“ESPP”). The Incentive Plan was most recently amended and restated on April 24, 2023 and approved by the Company’s stockholders on June 13, 2023. The Inducement Plan was most recently amended and restated by the Company’s Board of Directors on August 26, 2022. The ESPP was most recently amended and restated by the Company’s Board of Directors on July 7, 2023.

There was approximately $126,812 of total unrecognized compensation expense related to non-vested stock option and restricted stock unit awards granted by the Company as of June 30, 2023. As of June 30, 2023, the Company expected to recognize that expense as follows: $25,967 during the remainder of 2023, $47,207 in 2024, $34,593 in 2025, $18,582 in 2026 and $463 in 2027. In addition, the Company has outstanding performance-based stock options and restricted stock unit awards for which no compensation expense is recognized until “performance” has occurred and the award vests.

The Company grants stock option awards, restricted stock and restricted stock units to its employees, directors, and consultants under the Incentive Plan. Under the Incentive Plan, stock option awards are granted with an exercise price equal to the market price of the Company’s common stock at the date of grant. Stock option awards and restricted stock units granted to employees generally vest 25% each year until fully vested after four years.

In December 2014, the Company issued 1,250 performance-based stock options. These awards vest upon successful completion of specific development milestones. As of June 30, 2023, 85% of these grants have vested.

In January 2022, the Company issued 221 performance-based restricted stock unit awards. 21 of the awards met the performance objectives in 2022 and became eligible for vesting at 50% on the first anniversary of the grant date and 25% on each of the second and third anniversaries of the grant date, until fully vested after three years. The remaining awards were cancelled.

Stock option awards and restricted stock unit awards granted to non-employee directors of the Company generally vest over one year. Stock option awards granted to new non-employee directors when they first join the Company’s Board of Directors generally vest, subject to the terms of the Incentive Plan, in 36 equal monthly installments over a three-year period measured from the grant date. All stock option awards have contractual terms of 10 years. Restricted stock unit awards granted to new non-employee directors when they first join the Company’s Board of Directors generally vest, subject to the terms of the Incentive Plan, in three equal annual installments beginning on the first anniversary of the grant date. The vesting and exercise provisions of all awards granted under the Incentive Plan are subject to acceleration in the event of certain stockholder-approved transactions, or upon the occurrence of a change in control as defined in the Incentive Plan.


	Awards Available	Options Outstanding	Weighted Average Exercise Price
Balance December 31, 2022	4,206	31,179	$	8.56

Plan amendment	7,000	—	—
Restricted stock unit awards granted	(314)	—	—
Restricted stock unit awards cancelled	417	—	—
Stock option awards granted	(618)	618	9.01
Stock option awards exercised	—	(775)	5.25
Stock option awards cancelled	810	(810)	10.12
Balance June 30, 2023	11,501	30,212	$	8.61

For stock option awards granted under the Incentive Plan during the first six months of 2023 and 2022, the fair value was estimated on the date of grant using a Black-Scholes option pricing model and the assumptions noted in the table following the next subsection. The weighted average grant date fair value of these awards granted during the first six months of 2023 and 2022 was $6.40 and $7.78, respectively. The fair value of the stock option awards is amortized to expense over the vesting periods using a straight-line expense attribution method. For restricted stock unit awards granted under the Incentive Plan, the fair value of the awards was determined based on the market value of the Company’s shares on the grant date. The weighted average grant date fair value of these awards granted during the first six months of 2023 and 2022 was $9.18 and $13.25, respectively. The fair value of the restricted stock unit awards is amortized to expense over the vesting periods using a straight-line expense attribution method.

The Company has the ability to grant stock option and restricted stock unit awards to newly-hired employees as inducements material to each employee entering employment with the Company. Awards granted to newly hired employees generally vest 25% each year until fully vested after four years and are subject to the terms and conditions of the Inducement Plan. Each stock option has a term of 10 years. The vesting and exercise provisions of all awards granted under the Inducement Plan are subject to acceleration in the event of certain stockholder-approved transactions, or upon the occurrence of a change in control as defined in the Inducement Plan.


	Awards Available	Options Outstanding	Weighted Average Exercise Price
Balance December 31, 2022	947	5,341	$	8.80

Restricted stock unit awards granted	(325)	—	—
Restricted stock unit awards cancelled	61	—	—
Stock option awards granted	(801)	801	9.00
Stock option awards exercised	—	(330)	3.65
Stock option awards cancelled	460	(460)	9.97
Balance June 30, 2023	342	5,352	$	9.04

For stock option awards granted under the Inducement Plan during the first six months of 2023 and 2022, the fair value was estimated on the date of grant using a Black-Scholes option pricing model and the assumptions noted in the table below. The weighted average grant date fair value of these awards granted during the first six months of 2023 and 2022 was $6.38 and $10.28, respectively. The fair value of the stock option awards is amortized to expense over the vesting periods using a straight-line expense attribution method. For restricted stock unit awards granted under the Inducement Plan, the fair value of the awards was determined based on the market value of the Company’s shares on the grant date.

The weighted average grant date fair value of these awards granted during the first six months of 2023 and 2022 was $8.84 and $13.88, respectively. The fair value of the restricted stock unit awards is amortized to expense over the vesting periods using a straight-line expense attribution method.

The following table summarizes the key assumptions used by the Company to value the stock option awards granted under all plans during the first six months of 2023 and 2022, respectively. The expected life is based on the average of the assumption that all outstanding stock option awards will be exercised at full vesting and the assumption that all outstanding stock option awards will be exercised at the midpoint of the current date (if already vested) or at full vesting (if not yet vested) and the full contractual term. The expected volatility represents the historical volatility on the Company’s publicly-traded common stock. The Company has assumed no expected dividend yield, as dividends have never been paid to stock or option holders and will not be paid for the foreseeable future. The weighted average risk-free interest rate is the implied yield currently available on zero-coupon government issues with a remaining term equal to the expected term.

The Company has reserved a total of 7,975 shares of common stock to be purchased under the ESPP, of which 5,617 shares remain available for purchase as of June 30, 2023. Eligible employees may authorize up to 15% of their salary to purchase common stock at the lower of 85% of the beginning or 85% of the ending price during six-month purchase intervals. No more than three thousand shares may be purchased by any one employee at the six-month purchase dates, and no employee may purchase stock having a fair market value at the commencement date of $25 or more in any one calendar year. During the six months ended June 30, 2023, and 2022, the Company issued 176 and 115 shares under the ESPP, respectively. Compensation expense for shares purchased under the ESPP related to the purchase discount and the “look-back” option were determined using a Black-Scholes option pricing model.