The data here was presented at an ASCO plenary session by Dr. Kimberly Blackwell of Duke Medical Center. Note that, she also spoke separately at a Roche Investor Event later that same day and provided additional color around the data. You may want to listen to that on a webcast which remains available at Roche’s Investor website.
But turning to the data, the efficacy results continue to look very strong for T-DM1 and in particular in this study. What they confirmed was the significant improvement in PFS that they previously reported in topline data and while overall survivor data was not mature and was not expected to be mature, there was an insight into the overall survivor data.
First off, it was analyzed at this time because of the statistical plan called for interim analysis of overall survival when the PFS endpoint was reached. The study had been powered for overall survival analysis when 632 events occurred; these events being patient deaths. At the time, the PFS endpoint was reached only 223 events had occurred. Nonetheless, a hazard ratio was generated at 0.621 and that’s with the P value of 0.005. Dr. Blackwell noted that the data missed reaching statistical significance by just one event and I think that’s noteworthy when you have barely a third of the events that had been planned in the statistical design of the study.
What was learned that for evaluable patients at the time of the data cutoff, two years survival was 65.4% for patients receiving T-DM1 and that compares with 47.5% for patients receiving Tykerb plus Xeloda. And Dr. Blackwell described this difference as being huge. Obviously, a very encouraging trend for what one might expect to see as the patient population matures here.In terms of tolerability, Dr. Blackwell also noted that the drug exposure was high with the two HER2 targeted therapies with 93.4% for Tykerb and 99.9% for T-DM1. This contrast’s with a 77.2% exposure for Xeloda which Dr. Blackwell noted was what she would expect based on prior studies. 53% of the Xeloda patients had dose reductions, again reflecting tolerability issues. Read the rest of this transcript for free on seekingalpha.com