13D Filing: Baker Bros. Advisors and Idera Pharmaceuticals Inc. (IDRA)

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Page 2 of 10 – SEC Filing

CUSIP No.   45168K306   Page   2   of   10   Pages
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

NUMBER
OF SHARES
BENEFICIALLY
OWNED
BY EACH
REPORTING
PERSON WITH
7.

SOLE VOTING POWER:

18,619,136 (1)

8.

SHARED VOTING POWER:

0

9.

SOLE DISPOSITIVE POWER:

18,619,136 (1)

10.

SHARED DISPOSITIVE POWER:

0

11.

AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON:

18,619,136 (1)

12.

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

¨

13.

PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

9.9% (1)(2)

14.

TYPE OF REPORTING PERSON*

IA, PN

(1) Includes 151,667 shares of the common stock of Idera
Pharmaceuticals, Inc. (the “Issuer”) underlying options directly held by Julian C. Baker, a principal of Baker Bros.
Advisors LP (“the Adviser”), and 151,667 shares of the common stock of the Issuer underlying options directly held
by Dr. Kelvin M. Neu, an employee of the Adviser.
(2) Based on 183,013,693 shares of the Issuer’s common
stock that will be outstanding following the Offering (as defined below) including 5,000,000 shares issued as part of the Underwriter’s
option (as defined below) described in the Issuer’s Prospectus Supplement filed with the Securities and Exchange Commission
(the “SEC”) on October 26, 2017.

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