Aquinox Pharmaceuticals Inc (AQXP): Baker Bros. Advisors Pushes Stake to Over 45%

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)

o

6.

CITIZENSHIP OR PLACE OF ORGANIZATION

Delaware

7.

SOLE VOTING POWER

10,536,092

8.

SHARED VOTING POWER:

0

9.

SOLE DISPOSITIVE POWER:

10,536,092

10.

SHARED DISPOSITIVE POWER:

0

11.

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:

10,536,092

12.

CHECK
BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES (See Instructions)

¨

13.

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW
(11)

45.1%(1)

14.

TYPE OF REPORTING PERSON (See Instructions)

IA, PN