In June 2021 the Company's stockholders approved the 2021 Omnibus Equity Incentive Plan ("2021 Plan"). As of December 31, 2024 the number of authorized shares in the 2021 Plan is equal to the sum of (i) 8,150,000 shares, plus (ii) the number of shares of Common Stock reserved, but unissued under the 2014 Plan; and (iii) the number of shares of Common Stock underlying forfeited awards under the 2014 Plan. As of December 31, 2024, there were 3,159,005 shares available for issuance under the 2021 Plan.

Subsequent to the adoption of the 2021 Plan, no additional equity awards can be made under the terms of the 2014 Plan.

The Company issues equity awards to certain new employees as inducement grants outside of its 2021 Plan. As of December 31, 2024, an aggregate of 1,380,248 shares were issuable upon the exercise of inducement grant stock options approved by the Company.

In June 2023 the Company modified stock options for a departing employee. The modification resulted in an incremental stock-based compensation expense of $0.6 million during the year ended December 31, 2023.

On May 30, 2024, the Board of Directors of the Company approved the rescinding of an aggregate of 1,697,712 shares of common stock issuable upon exercise of stock options granted on March 7, 2024 at an exercise price of $3.51 per share to employees and officers of the Company. On May 30, 2024, the Board of Directors of the Company approved the grant of an aggregate of 1,697,712 shares of common stock issuable upon exercise of stock options at an exercise price of $3.51 per share to employees and officers of the Company, subject to stockholder approval of an increase in the shares of common stock available for issuance pursuant to the Company’s 2021 Equity Incentive Plan at the Company’s annual meeting on June 20, 2024. The increase of shares available was approved by shareholders at the June 20, 2024 meeting, thus completing the requirements for the reissuance of the grant. The terms of the reissued grant were identical to the rescinded grant, therefore the transaction does not represent a stock option modification.

Stock-based compensation has been recognized in operating results as follows:


(in thousands)	Years ended December 31,
	2024		2023
Research and development expenses	$	1,660	$	1,279
Selling, general and administrative expenses		3,100		3,230
Total stock-based compensation	$	4,760	$	4,509

The estimated fair value of stock option awards was determined on the date of grant using the Black-Scholes option valuation model with the following assumptions during the years indicated below:


	Years ended December 31,
	2024	2023
Risk-free interest rate (range)	4.04% - 4.27%	3.56% - 4.06%
Dividend yield	0%	0%
Expected volatility (range)	103% - 107%	105% - 110%
Expected term (in years)	5.8 years	5.2 years

Risk-free interest rate — Based on the daily yield curve rates for U.S. Treasury obligations with maturities that correspond to the expected term of the Company’s stock options.

Dividend yield — Cardiff Oncology has not paid any dividends on common stock since its inception and does not anticipate paying dividends on its common stock in the foreseeable future.

Expected volatility — Based on the historical volatility of Cardiff Oncology’s common stock.

Expected term — The expected term for options granted after January 1, 2023 is estimated based on the Company's historical employee data.

Forfeitures — The Company estimates forfeitures based on its historical experience.

The weighted-average fair value per share of all options granted during the years ended December 31, 2024 and 2023, estimated as of the grant date using the Black-Scholes option valuation model, was $2.79 and $1.35 per share, respectively.

The unrecognized compensation cost related to non-vested stock options outstanding at December 31, 2024 was $7.0 million. The weighted-average remaining amortization period at December 31, 2024 for non-vested stock options was 2.2 years.

The total fair value of shares vested during the years ended December 31, 2024 and 2023 was $4.6 million and $4.8 million, respectively.

A summary of stock option activity and of changes in stock options outstanding is presented below:


	Number of Options			Weighted- Average Exercise Price Per Share		Intrinsic Value		Weighted- Average Remaining Contractual Life
Balance outstanding, December 31, 2023		6,650,954		$	4.27	$	23,926	7.9 years
Granted		1,905,096		$	3.40
Exercised		(139,430	)	$	2.67	$	139,371
Forfeited and expired		(81,855	)	$	26.39
Balance Outstanding, December 31, 2024		8,334,765		$	3.88	$	11,668,989	7.5 years
Vested and exercisable, December 31, 2024		4,723,009		$	4.48	$	6,404,133	6.7 years
Vested and expected to vest, December 31, 2024		8,132,737		$	3.91	$	11,344,268	7.4 years