Idera Pharmaceuticals, Inc. (Nasdaq: IDRA) announced today the presentation of data from a four-week Phase 1 clinical trial of IMO-2125 in combination with ribavirin in treatment-naïve patients chronically infected with hepatitis C virus (HCV) genotype 1. During the four weeks of treatment, IMO 2125 in combination with ribavirin was well tolerated and produced clinically meaningful antiviral activity. IMO 2125 is a Toll-like Receptor 9 (TLR9) agonist that stimulates production of natural interferons and other antiviral cytokines. The presentation (Abstract #1209), entitled "IMO-2125 plus ribavirin gives substantial first-dose viral load reductions, cumulative antiviral effect, is well tolerated in naïve genotype 1 HCV patients: a Phase 1 trial", was made at the 46th Annual Meeting of the European Association for the Study of the Liver (EASL) being held in Berlin, Germany from March 30 - April 3, 2011. The presentation provided additional detail from the trial for which interim data was announced in December 2010.

"This study provides several key results that support our IMO-2125 development program," said Robert Arbeit, M.D., Vice President of Clinical Development at Idera. "First, IMO-2125 in combination with ribavirin had substantial antiviral activity in treatment-naïve patients. This antiviral activity was associated with decreases in serum liver enzyme levels over the four-week course of treatment. Second, IMO-2125 was well tolerated, and demonstrated important safety features in comparison to Pegasys® used in the control arm. These included shorter duration of flu-like symptoms and minimal hematologic toxicity, with no IMO-2125-treated patients developing neutropenia requiring intervention or platelet levels below lower limits of normal."

Dr. Arbeit continued, "We are preparing to initiate a 12-week Phase 2 clinical trial of IMO-2125 plus ribavirin in treatment-naïve genotype 1 HCV patients in the second quarter of 2011. We expect to use data from that study to select dosages for subsequent clinical trials of IMO-2125 in combination with ribavirin and a direct acting antiviral agent."

"We have now completed Phase 1 clinical evaluation of IMO-2125 in both treatment-naïve and null-responder HCV patients and have established that its immune stimulation mechanism of action provides clinically meaningful antiviral activity and is well tolerated," said Tim Sullivan, Ph.D., Vice President of Development Programs and Alliance Management at Idera. "By the end of this year we expect to have completed chronic nonclinical safety studies to support further clinical development of IMO-2125 as an immune modulatory component of HCV therapy."

"Our objective is to develop a novel immune modulator for the treatment of HCV as a potential alternative to pegylated interferons," said Sudhir Agrawal, D.Phil., Chairman and Chief Executive Officer at Idera. "We have confirmed the intended mechanism of action of IMO-2125 and are very pleased with its safety profile and antiviral activity in both null-responder and treatment-naïve HCV patients. We look forward to initiating the Phase 2 clinical trial, which we expect will provide the additional data needed to advance the clinical development of IMO-2125 and support studies in combination with direct-acting antiviral agents."

Phase 1 Clinical Trial in Treatment-naive HCV Patients

Study Design:

In this Phase 1 clinical trial, treatment-naïve genotype 1 HCV patients received IMO-2125 by subcutaneous injection over four weeks in combination with daily oral administration of standard, weight-based doses of ribavirin in one of four treatment regimens of 12 patients each. The four regimens of IMO-2125 were 0.08, 0.16, and 0.32 mg/kg once weekly and 0.16 mg/kg twice weekly.In addition, 12 patients received Pegasys®plus ribavirin. Study endpoints of safety and antiviral activity were measured through Day 29. Upon completion of the four weeks of protocol-specified treatment, all patients received follow-on treatment with Pegasys®plus ribavirin. Under the trial protocol, final safety and antiviral assessments were taken at Day 59, four weeks after the follow-on treatment with Pegasys®plus ribavirin was initiated.

Study Results:

Patient Population

All patients were Caucasian, except one Asian patient in the 0.16 mg/kg/week IMO-2125 group; all were infected with HCV genotype 1. Additional demographic and baseline data are summarized in the following table.

Cohort IMO-2125 Regimen† (mg/kg/wk)NAge over 50IP-10 over 600 pg/mL Male Sex Baseline Log10 HCV RNA (mean ± SD)IL28B CT or TT 10.08123 (25%)2 (16%)9 (75%)6.4 + 0.7not available 20.161201 (8%)8 (67%)6.6 + 0.6pending* 2Pegasys®601(16%)4 (67%)6.5 + 0.9pending* 30.32125 (42%)4 (33%)7 (58%)6.2 + 0.59 (75%) 30.16 2x/wk123 (25%)5 (42%)5 (42%)6.5 + 0.49 (75%) 3Pegasys®63 (50%)1 (16%)5 (42%)6.6 + 0.23 (50%)

† All subjects received weight-based ribavirin
* IL28B genotyping results are pending.

Safety

- IMO 2125 was well tolerated at all dose levels in combination with ribavirin over four weeks of treatment, with no treatment-related serious adverse events and no treatment discontinuations. The most common adverse events observed in the IMO-2125 regimens were mild to moderate flu-like symptoms and injection site reactions.

- Flu-like symptoms. Among patients who received IMO-2125, flu-like symptoms consisted primarily of fever and chills with onset within approximately eight hours of dosing and of brief duration, typically lasting less than one day. In contrast, the observations for the patients receiving Pegasys® who experienced flu-like symptoms were consistent with the extensively published experiences showing that flu-like symptoms generally include malaise and fatigue, have delayed onset at one or two days after dosing, and often last two days or more.

- Neutropenia. Neutropenia (absolute neutrophil count (ANC)