Time Is No Friend To Synta's Lung Cancer Drug

LEXINGTON, Mass. (TheStreet) -- This weekend's update from Synta Pharmaceutical's (SNTA) ganetespib phase II study makes the experimental lung cancer drug look weaker and more irrelevant than ever before.

Synta insists the new ganetespib data are positive and "increases confidence" in a successful outcome from the ongoing phase III lung cancer study.

So far, the market hasn't bought Synta's spin job and it's hard to imagine this weekend's ganetespib data improve investor sentiment. SNTA data by YCharts

The phase II "Galaxy-1" study randomizes 252 patients with advanced (second line) non-small cell adenocarcinoma to treatment with ganetespib and docetaxel or docetaxel alone. One-year follow-up results from the study are being presented at the 15th World Conference on Lung Cancer in Sydney, Australia. [Bristol-Myers Squibb (BMY) is presenting an update on its PD-1 inhibitor nivolumab at the same lung cancer conference, which is drawing the most attention and excitement.] The latest look at the study has ganetespib/docetaxel reducing the risk of death by 10% compared to docetaxel alone. (That's a hazard ratio of 0.90, not statistically significant.) At the median, patients treated with ganetespib/docetaxel are living 10.4 months compared to 8.4 months for patients treated with docetaxel alone -- a benefit of two months that is not statistically significant. Last June, with median follow up of six months, ganetespib/docetaxel reduced the risk of death by 18% compared to docetaxel alone. (Hazard ratio of 0.82, not statistically significant.) The median overall survival benefit last June was 2.4 months. In September 2012, the hazard ratio from the Galaxy-1 study was 0.69, or a 31% reduction in the risk of death favoring gantespib/docetaxel. Synta has now provided three significant updates of the Galaxy-1 study and each time, the benefit demonstrated by ganetespib wanes. Ganetespib's efficacy is deteriorating even in the cherry-picked subset of patients from the Galaxy-1 study which Synta's describes as "normal progressors." These are lung cancer patients who were stable (no tumor growth) following first-line treatment for at least six months. Synta limited enrollment in the ongoing phase III study to these "normal progressor" patients because the company claims they respond best to ganetespib. After one year of follow up, the overall survival hazard ration for these "normal progressor" patients is 0.75 -- a 25% reduction in the risk of death favoring ganetespib/docetaxel compared to docetaxel alone. The difference is not statistically significant. Last June, the overall survival hazard ratio for "normal progressors" was 0.61 -- a 39% reduction in the risk of death The median overall survival for "normal progressors" treated with ganetespib/docetaxel is 10.7 months compared to 7.4 months for "normal progressors" treated with docetaxel -- a median survival benefit of 3.3 months. But check this out, the median overall survival for "normal progressors" (10.7 months) in the ganetespib arm of the study is essentially the same as the 10.4 months for all patients. The only reason "normal progressors" appear to be benefitting more in the study is because the docetaxel control arm is performing worse (7.4 months vs. 8.4 months.) This is the flimsy evidence upon which Synta expresses confidence ganetespib and the ongoing phase III study. No wonder investors are skeptical. -- Reported by Adam Feuerstein in Boston. Follow @AdamFeuerstein