X0305 4 2012-03-29 0 0000861838 IDERA PHARMACEUTICALS, INC. IDRA 0001443689 Senator Investment Group LP 510 MADISON AVENUE 28TH FLOOR NEW YORK NY 10022 0 0 1 0 Common Stock 2012-03-29 4 S 0 49381 1.92 D 3185124 I See Footnote Common Stock 2012-03-30 4 S 0 11624 1.90 D 3173500 I See Footnote Common Stock 2012-03-30 4 S 0 50000 1.87 D 3123500 I See Footnote The entities and individuals identified in this Form 4 (the "Reporting Persons") disclaim any membership in any "group". The amount of securities shown in this row is owned by Senator Global Opportunity Master Fund L.P. (the "Master Fund"). As Investment Manager to the Master Fund, Senator Investment Group LP ("Senator LP") may be deemed to be the beneficial owner of the Issuer's securities owned by the Master Fund, but disclaiming beneficial ownership to the extent such beneficial ownership exceeds its pecuniary interest. Douglas Silverman, a United States citizen, and Alexander Klabin, a United States citizen, have control of a Delaware limited liability company that may be deemed to control Senator LP. Each of Messrs. Silverman and Klabin disclaim beneficial ownership of the shares owned by the Master Fund to the extent such beneficial interest exceeds his pecuniary interests. Edward Larmann, Chief Operating Officer 2012-04-04