In June 2021 the Company's stockholders approved the 2021 Omnibus Equity Incentive Plan ("2021 Plan"). The number of authorized shares in the 2021 plan is equal to the sum of (i) 3,150,000 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. On June 9, 2022 the shareholders approved an increase of shares authorized in the 2021 Plan to 5,150,000. As of December 31, 2023, there were 2,013,871 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.

In July 2021, the Company began issuing equity awards to certain new employees as inducement grants outside of its 2021 Plan. As of December 31, 2023, an aggregate of 1,435,256 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.

In June 2022 one of the Company's directors did not seek another term on the Board of Directors. At the time of departure, the Compensation Committee passed a resolution to extend the expiration date of the vested stock options, and to immediately accelerate the vesting of the unvested options. The Company recorded incremental reduction to stock compensation expense of $0.1 million during the year ended December 31, 2022, related to the modifications.


(in thousands)	Years ended December 31,
	2023		2022

Research and development expenses	$	1,279	$	1,035

Selling, general and administrative expenses	3,230		3,221

Total stock-based compensation	$	4,509	$	4,256

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,
	2023	2022
Risk-free interest rate (range)	3.56% - 4.06%	1.62% - 3.75%
Dividend yield	0%	0%
Expected volatility (range)	105% - 110%	98% - 110%
Expected volatility (weighted-average)	109%	106%
Expected term (in years)	5.2 years	6.0 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 term — The expected term for options granted after January 1, 2023 is estimated based on the Company's historical employee data. Prior to January 1, 2023, the Company used the "simplified method" to estimate expected term.

The weighted-average fair value per share of all options granted during the years ended December 31, 2023 and 2022, estimated as of the grant date using the Black-Scholes option valuation model, was $1.35 and $2.55 per share, respectively.

The unrecognized compensation cost related to non-vested stock options outstanding at December 31, 2023 was $6.6 million. The weighted-average remaining amortization period at December 31, 2023 for non-vested stock options was 2.1 years.

The total fair value of shares vested during the years ended December 31, 2023 and 2022 was $4.8 million and $4.7 million, respectively.


	Number of Options	Weighted-Average Exercise Price Per Share		Intrinsic Value		Weighted-Average Remaining Contractual Life














Balance outstanding, December 31, 2022	5,069,458	$	5.92	$	19,322	7.4 years
Granted	2,138,624	$	1.70


Forfeited and expired	(557,128)	$	9.43
Balance Outstanding, December 31, 2023	6,650,954	$	4.27	$	23,926	7.9 years
Vested and exercisable, December 31, 2023	3,124,492	$	5.66	$	22,456	6.9 years
Vested and expected to vest, December 31, 2023	6,462,464	$	4.33	$	23,853	7.8 years