Cubist Ends Drug Trial - Analyst Blog

Cubist Pharmaceuticals Inc. (CBST) has stopped a mid-stage trial of one of its pipeline candidates, CB-500,929 (ecallantide). The drug was being studied for lowering blood loss in patients undergoing cardiac surgery using cardiopulmonary bypass (CPB). 

The decision to stop the trial was taken following a review of safety and efficacy data from two phase II trials – CONSERV 1 and CONSERV 2. However, this does not impact the 2010 R&D cost guidance as it did not include the cost of development of ecallantide beyond the CONSERV trials. 

The CONSERV 1 trial was conducted on 249 patients undergoing Coronary Artery Bypass Graft (CABG) Surgery using CPB. No improvement in blood loss was observed in patients who were administered CB-500,929 in three dosages of 5, 25 or 75 mg compared to placebo. 

The CONSERV 2 trial was conducted on 218 patients undergoing cardiac surgery using CPB for procedures including repeat sternotomy, CABG plus valve replacement or more than one valve replacement. The patient population in this trial is considered to be at a higher risk of bleeding complications, compared to those undergoing a primary CABG surgery. 

The safety and efficacy of the 75 mg dosage of CB-500,929 administered on patients was compared with patients treated with tranexamic acid. Here also, no treatment benefit was observed in patients administered with CB-500,929. To make things worse, a significantly higher rate of mortality was observed in patients treated with CB-500,929, compared to those treated with tranexamic acid. 

Due to the increase in mortality, Cubist ended enrollment in the CONSERV 2 trial early in December 2009. Subsequently, the company also ended enrollment early in CONSERV 1 trial as a precautionary measure although no such mortality imbalance was observed in CONSERV 1 results. 

As a result of the decision to end development of CB-500,929, Cubist in due course will terminate its 2008 agreement with Dyax Corp. (DYAX) under which it in-licensed development and commercialization rights of the drug in the US and the EU.
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