Sophiris Bio Inc. Tanks As Phase 3 Data Indicates Drug May Not Be Effective

December 15, 2014
By Riley McDermid, BioSpace.com Breaking News Sr. Editor

Shares of Sophiris Bio Inc. tanked almost 75 percent in morning trading Monday, after the company said its new prostate drug PRX302 (topsalysin) had flunked a Phase III trial and had not demonstrated efficacy at treating symptoms.

Sophiris had been testing the drug on the treatment of symptoms of benign prostatic hyperplasia (BPH, enlarged prostate) and localized prostate cancer. Its “PLUS-1” trial of PRX302 was a look at how well it worked as a treatment for lower urinary tract symptoms of BPH.

But Sophiris said Monday the Independent Data Monitoring Committee (IDMC) reported that a predefined efficacy threshold following treatment was not achieved. This administrative interim analysis was conducted specifically for planning subsequent clinical trials.

Still, the company said the ongoing “PLUS-1” study is "unaffected by this recommendation," and all patients in the study will continue to be followed to enable the evaluation of the primary efficacy endpoint at 52 weeks.

“Patients will continue to be followed for the duration of the study to evaluate the International Prostate Symptom Score (IPSS) total score change from baseline over 52 weeks–the primary endpoint of the study,” said Randall Woods, president and CEO of Sophiris, in a statement. “We expect to be able to provide further commentary on the activity of PRX302 once the study is complete and all the data through 52 weeks are unblinded and analyzed in the fourth quarter of 2015.”

The IDMC completed the planned, protocol-specified administrative analysis of efficacy based on the IPSS change from baseline to Week 12 for all 479 patients dosed in the study. Sophiris added that the IDMC completed its fifth and final periodic analysis of unblinded safety data and had reported no safety concerns.

"There were no events of sepsis reported post administration of study drug in this trial," said the company.

"The IDMC conveyed this recommendation to Sophiris in a manner that would not unblind the study nor reveal the actual measured treatment effect," it said. "Sophiris and others directly involved in the study will remain blinded to treatment group assignment as the 52 week monitoring period continues until after the last patient has completed the study, which is anticipated to be in September 2016."