Acadia Pharmaceuticals (ACAD): Baker Bros. Advisors Buys More Shares

1.

NAMES OF REPORTING PERSONS

Baker Bros. Advisors LP

2.

CHECK
THE APPROPRIATE BOX IF A MEMBER OF A GROUP*      (a) ¨

                                                                                                                        (b) ¨

3.

SEC USE ONLY

4.

SOURCE OF FUNDS*

OO

5.

CHECK
BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEM 2(d) or 2(e)      ¨

6.

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

7.

SOLE VOTING POWER: 25,878,893 (1)

8.

SHARED VOTING POWER: 0

9.

SOLE DISPOSITIVE POWER: 25,878,893 (1)

10.

SHARED DISPOSITIVE POWER: 0

11.

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:
25,878,893 (1)

12.

CHECK
BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*      ¨

13.

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

21.6% (1)(2)

14.

TYPE OF REPORTING PERSON*

IA, PN