The Company incurred stock-based compensation expenses of $2.1 million and $4.4 million for the three and six months ended June 30, 2024, respectively, and $3.5 million and $6.0 million for the three and six months ended June 30, 2023, respectively.


			June 30, 2024		December 31, 2023
Title of Plan	Group Eligible	Type of Award Granted (or to be Granted)	Awards Outstanding	Additional Awards Authorized for Grant	Awards Outstanding	Additional Awards Authorized for Grant
Keryx Equity Plans(1)(2)	Employees, directors and consultants	Stock options and RSUs	208,986	—	232,203	—
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (2) (3) (the 2014 Plan)	Employees, directors, consultants and advisors	Stock options, RSUs, SARs and performance awards	12,597,753	—	15,311,501	—
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan(3) (the 2023 Plan) (replaced 2014 Plan)	Employees, officers, directors, consultants and advisors	Stock options, SARs, restricted stock, unrestricted stock, RSUs, performance awards, other share-based awards and dividend equivalents	10,435,850	—	1,712,400	17,382,722

(1) The Keryx Equity Plans consist of the Keryx Biopharmaceuticals, Inc. 1999 Share Option Plan, Keryx Biopharmaceuticals, Inc., as amended, the 2004 Long-Term Incentive Plan, as amended, the Keryx Biopharmaceuticals, Inc. 2007 Incentive Plan, the Keryx Biopharmaceuticals Inc. Amended and Restated 2013 Incentive Plan and the Keryx Biopharmaceuticals, Inc. 2018 Equity Incentive Plan.

(3) This table includes inducement awards that are subject to the terms and conditions of the applicable plan but were granted as inducement awards consistent with Nasdaq Listing Rule 5635(c)(4) and not under the applicable plan: 1,496,428 options included as outstanding under the 2014 Plan in the table and 2,374,950 options included as outstanding under the 2023 Plan in the table as of June 30, 2024 and 1,616,019 options included as outstanding under the 2014 Plan and 794,000 options included as outstanding under the 2023 Plan in the table as of December 31, 2023.

During the six months ended June 30, 2024, the Company issued 3,432,500 options to employees under the 2023 Plan. Options and SARs granted by the Company generally vest over periods of between 12 and 48 months, subject, in each case, to the individual’s continued service through the applicable vesting date. Options and SARs generally vest either 100% on the first anniversary of the grant date or in installments of (i) 25% at the one year anniversary and (ii) 12 equal quarterly installments beginning after the one year anniversary of the grant date, subject to the individual’s continuous service with the Company. Options and SARs generally expire ten years after the date of grant.

The Company also maintains an inducement award program with a share pool that is separate from the Company's equity plans under which inducement awards may be granted consistent with Nasdaq Listing Rule 5635(c)(4). During the six months ended June 30, 2024, the Company granted 1,604,950 options to purchase shares of the Company’s common stock to new hires as inducements to such employees entering into employment with the Company, of which 1,604,950 options remained outstanding as of June 30, 2024.

The Company grants annual service-based stock options to employees and directors and SARs to certain executives under the 2023 and 2014 Plans. In addition, the Company issues stock options to directors, new hires and occasionally to other employees not in connection with the annual grant process.

Finally, the Company grants performance-based stock options which generally vest in connection with the achievement of specified commercial, regulatory and corporate milestones. The performance-based stock options also generally feature a time-based vesting component. The expense recognized for these awards is based on the grant date fair value of the Company’s common stock multiplied by the number of options granted and recognized over time based on the probability of meeting such commercial, regulatory and corporate milestones.


	Stock Options	Weighted Average Exercise Price		Weighted-Average Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023	13,312,835	$	4.20	7.27 years	—
Granted	5,037,450	$	1.57	—	—
Exercised	(304,152)	$	0.51	—	—
Expired	(119,043)	$	21.02
Canceled and forfeited	(648,270)	$	3.11	—	—
Outstanding at June 30, 2024	17,278,820	$	3.42	7.37 years	$	1,521
Exercisable at June 30, 2024	8,559,257	$	5.40	5.59 years

As of June 30, 2024, there was approximately $9.3 million of unrecognized compensation costs related to stock options, which is expected to be recognized over a weighted average period of 2.94 years.

Generally, restricted stock units, or RSUs, granted by the Company vest in one of the following ways: (i) 100% of each RSU grant vests on the first anniversary of the grant date, (ii) one third of each RSU grant vests on the first, second and third anniversaries of the grant date, or (iii) one third of each RSU grant vests on the first anniversary of the grant date and the remaining two thirds vests in eight substantially equal quarterly installments beginning after the one year anniversary, subject, in each case, to the individual’s continued service through the applicable vesting date. The grant-date fair value of the RSUs is recognized as expense on a straight-line basis. The Company determines the fair value of the RSUs based on the closing price of the common stock on the date of the grants.

The Company also periodically grants performance-based restricted stock units, or PSUs, to employees under the 2023 Plan and previously granted PSUs under the 2014 Plan. The PSUs granted by the Company generally vest in connection with the achievement of specified commercial, regulatory and corporate milestones. The PSUs also generally feature a time-based vesting component. The expense recognized for these awards is based on the grant date fair value of the Company’s common stock multiplied by the number of units granted and recognized over time based on the probability of meeting such commercial, regulatory and corporate milestones.


	2014 Plan			2023 Plan
	Number of Shares	Weighted Average Fair Value		Number of Shares	Weighted Average Fair Value
Outstanding as of December 31, 2023	3,339,869	$	1.30	603,400	$	1.48
Granted	—	$	—	3,968,200	$	1.59
Vested	(1,478,822)	$	1.62	(210,000)	$	1.20
Forfeited and canceled	(210,678)	$	0.90	(48,200)	$	1.68
Outstanding as of June 30, 2024	1,650,369	$	1.07	4,313,400	$	1.59

As of June 30, 2024, there was $7.3 million of unrecognized compensation costs related to time-based RSUs and PSUs, which is expected to be recognized over a weighted-average period of 2.25 years.

On June 6, 2019, the Company's stockholders approved the Amended and Restated 2014 Employee Stock Purchase Plan, or ESPP. Under the ESPP substantially all employees may voluntarily enroll to purchase shares of the Company’s 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 the six-month offering period. An employee's payroll deductions under the ESPP are limited to 15% of the employee's compensation, and an employee may not purchase more than $25,000 worth of stock during any calendar year. In addition, an employee may not purchase more than 1,500 shares in any offering period. As of June 30, 2024 and December 31, 2023, a total of 4,545,480 and 4,637,801 shares of the Company’s common stock were available for future issuance under the ESPP, respectively. The Company issued 92,321 shares under the ESPP during the six months ended June 30, 2024.

The Black-Scholes option pricing model is used to estimate the fair value of the stock options. The weighted-average assumptions used in calculating the fair values of the rights to acquire stock under the 2023 Plan, the 2014 Plan and inducement awards were as follows:


	Three Months Ended June 30,								Six Months Ended June 30,
Stock Options	2024				2023				2024			2023
Risk-free interest rate	4.24	%	-	4.66%	3.67	%	-	3.99%	3.90%	-	4.66%	3.54%	-	3.99%
Expected volatility	109.98	%	-	118.61%	102.31	%	-	111.71%	109.98%	-	118.61%	100.97%	-	111.71%
Expected term (years)	5.51 years		-	6.25 years	5.51 years		-	6.25 years	5.51 years	-	6.25 years	5.51 years	-	6.25 years
Expected dividend yield	—%				—%				—%			—%
Weighted average grant date fair value	$0.91				$0.97				$1.35			$0.56

The Company has classified stock-based compensation in its unaudited condensed consolidated statements of operations and comprehensive loss as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Cost of goods sold	$	83	$	73	$	169	$	139
Research and development	396		532		815		1,202
Selling, general and administrative	1,593		2,685		3,410		4,220
Restructuring	—		200		38		418
Total stock-based compensation	$	2,072	$	3,490	$	4,432	$	5,979