In August 2020, the Company entered into an Agreement and Plan of Merger (the Merger Agreement) with CerSci Therapeutics Incorporated (CerSci), pursuant to which one of the Company’s wholly owned subsidiaries merged with and into CerSci, with CerSci as the surviving corporation and the Company’s wholly owned subsidiary. Approximately 1.2 million shares of the Company’s common stock with a value of $44.3 million were issued to CerSci’s former equity holders. The Company filed a registration statement on Form S-3 with the SEC to register the resale of the shares of the Company’s common stock issued in connection with its acquisition of CerSci.

In September 2019, the Company raised net proceeds of approximately $271.5 million from the sale of 7,187,500 shares of its common stock in a follow-on public offering, including 937,500 shares sold pursuant to the exercise in full of the underwriters’ option to purchase additional shares.

The Company’s 2010 Equity Incentive Plan, as amended to date (the 2010 Plan), permits the grant of options to employees, directors and consultants. In addition, the 2010 Plan permits the grant of stock bonuses, rights to purchase restricted stock, and other stock awards. The exercise price of options granted under the 2010 Plan cannot be less than 100 percent of the fair market value of the common stock on the date of grant and the maximum term of any option is 10 years. Options granted under the 2010 Plan generally vest over a four-year period. All shares that remained eligible for grant under the Company’s 2004 Equity Incentive Plan (the 2004 Plan) at the time of approval of the 2010 Plan were transferred to the 2010 Plan. The 2010 Plan share reserve also has been, and may be, increased by the number of shares that otherwise would have reverted to the 2004 Plan reserve after June 2010. In June 2015, June 2016, June 2017, June 2018, and June 2019, the Company’s stockholders approved amendments to its 2010 Plan to, among other things, increase the aggregate number of shares of common stock authorized for issuance under the plan by 5,000,000 shares, 3,000,000 shares, 5,500,000 shares, 6,700,000 shares, and 8,300,000 shares, respectively. At December 31, 2020, there were 28,426,504 shares of common stock authorized for issuance, of which 9,777,263 shares were available for new grants under the 2010 Plan.

The 2010 Plan provided for the grant of options to employees, directors and consultants. The exercise price of options granted under the 2010 Plan was at 100 percent of the fair market value of the common stock on the date of grant and the maximum term of any option was 10 years. Options granted under the 2010 Plan generally vested over a four-year period.

The following table summarizes the Company’s stock option activity during the year ended December 31, 2020:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019		17,427,228		$	28.69
Granted		1,937,006		$	43.78
Exercised		(2,571,633	)	$	28.71
Cancelled/forfeited		(350,607	)	$	31.75
Outstanding at December 31, 2020		16,441,994		$	30.40		6.8	$	379,233
Vested at December 31, 2020		9,691,855		$	29.71		6.0	$	230,156
Unvested at December 31, 2020		6,750,139		$	31.38		8.0	$	149,078
Exercisable at December 31, 2020		9,691,855		$	29.71		6.0	$	230,156

The aggregate intrinsic value of options exercisable as of December 31, 2020 is calculated as the difference between the exercise price of the underlying options and the closing market price of the Company’s common stock on that date, which was $53.46 per share. The aggregate intrinsic value of options exercised during the years ended December 31, 2020, 2019, and 2018 was approximately $55.5 million, $56.6 million, and $11.2 million, respectively, determined as of the date of exercise. The Company received $73.8 million in cash from options exercised during the year ended December 31, 2020.

The weighted average per share fair value of options granted during the years ended December 31, 2020, 2019, and 2018 was approximately $24.16, $15.97, and $12.14, respectively. As of December 31, 2020, total unrecognized compensation cost related to stock options was approximately $99.1 million, and the weighted average period over which this cost is expected to be recognized is approximately 2.5 years.

The Company grants RSUs and PSUs, both of which are considered restricted stock, pursuant to the 2010 Plan and satisfies such grants through the issuance of new shares. RSUs are share awards that, upon vesting, will deliver to the holder shares of the Company’s common stock. RSUs generally vest over a four-year period. PSUs for which the number of shares issuable at the end of performance period can reach up to 200% of the shares approved in the award based on the achievement of certain pre-defined Acadia-specific performance criteria and continued employment through the vesting period.

The following table summarizes the Company’s restricted stock activity during the year ended December 31, 2020:

	Number of Shares			Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019		1,445,163		$	24.50
Granted		1,079,727		$	44.03
Vested		(255,953	)	$	23.83
Cancelled/forfeited		(61,690	)	$	35.95
Outstanding at December 31, 2020		2,207,247		$	33.81	$	117,999

700,156 and 448,632 PSUs were outstanding at December 31, 2020 and 2019, respectively. During the years ended 2020 and 2019, 255,878 and 481,036 PSUs were granted, respectively, none of which was vested. At December 31, 2020, total intrinsic value of PSUs outstanding was $37.4 million. As of December 31, 2020, total unrecognized compensation cost related to RSUs and PSUs was approximately $41.7 million and 2.6 million, respectively, and the weighted average period over which the cost is expected to be recognized is approximately 2.7 years and 1.5 years, respectively.

The Company’s 2004 Employee Stock Purchase Plan (the Purchase Plan) became effective upon the closing of the Company’s initial public offering in June 2004. In June 2016, June 2019 and June 2020, the Company’s stockholders approved an amendment to the Purchase Plan to, among other things, increase the aggregate number of shares of common stock authorized for issuance under the plan by 400,000 shares, 600,000 shares and 3,000,000 shares, respectively. At December 31, 2020, a total of 5,525,000 shares of common stock had been reserved for issuance under the Purchase Plan. At December 31, 2020, 3,106,995 shares of common stock remained available for issuance pursuant to the Purchase Plan. Eligible employees who elect to participate in an offering under the Purchase Plan may have up to 15 percent of their earnings withheld, subject to certain limitations, to purchase shares of common stock pursuant to the Purchase Plan. The price of common stock purchased under the Purchase Plan is equal to 85 percent of the lower of the fair market value of the common stock at the commencement date of each offering period or the relevant purchase date. During the years ended December 31, 2020, 2019, and 2018, a total of 377,963, 269,037, and 233,720 shares of common stock were issued under the Purchase Plan at average per share prices of $18.94, $16.41, and $15.75, respectively. The weighted average per share fair value of purchase rights granted during the years ended December 31, 2020, 2019, and 2018 was $22.47, $14.24, and $8.25, respectively. During the years ended December 31, 2020, 2019, and 2018, the Company recorded cash received from the exercise of purchase rights of $7.2 million, $4.4 million, and $3.7 million, respectively.