Medivation's Prostate Cancer Drug: Survival Benefit With Low Seizure Risk

SAN FRANCISCO (TheStreet) -- A researcher reconfirmed Tuesday the survival benefit for Medivation's(MDVN) MDV3100 in patients with advanced prostate cancer and said seizures attributed to the experimental drug came in at a low 0.6% in a late-stage clinical trial.

Medivation receiving a clean safety report for MDV3100 has been a pressing item on the agenda of biotech investors since November when the company first announced positive top-line results from a phase III study in which MDV3100 significantly reduced the risk of prostate cancer death by 37%.

Five of 800 patients treated with MDV3100 in the study reported seizures compared to zero seizures among placebo-treated patients, said Dr. Howard Scher of New York's Memorial Sloan-Kettering Cancer Center.

The 0.6% seizure rate attributed to MDV3100 is below the approximate 1.5% rate seen in an earlier study of the drug using higher doses and should assuage investor concerns about MDV3100's safety profile

J.P. Morgan biotech analyst Geoff Meacham counseled clients to be relieved if MDV3100's seizure rate fell to 1% or less. Likewise, Bernstein analyst Geoff Porges was expecting a seizure rate of 1-3% that slightly favored placebo over MDV3100.

Scher, the principal investigator of the MDV3100 phase III study, discussed the results with the media Tuesday on a call sponsored by the American Society of Clinical Oncology ahead of a symposium on genitourinary cancer that starts Thursday.

Medivation shares closed Tuesday at $55.41 and are up 235% since the MDV3100 results were first announced on November 2.

The phase III study enrolled men with advanced prostate cancer previously treated with chemotherapy. In the interim analysis, men treated with MDV3100, a pill, reported a median survival of 18.4 months compared to 13.6 months for men treated with a placebo -- or a 4.8-month survival benefit favoring MDV3100.

Analyzed another way, the risk of a man dying of prostate cancer while being treated with MDV3100 was reduced by 37%. The results from the interim analysis were statistically significant, which is why the study was stopped early.

The most common adverse events occurring more frequently in MDV3100 patients than the placebo group included fatigue, diarrhea and hot flashes, said Scher. Importantly, seizure was not on the list.