Merck ( MRK) is developing its own hepatitis C drug boceprevir and is the closest competitor to Vertex. In August, Merck announced results from phase III studies showing that treatment with boceprevir led to a 66% cure rate in treatment-resistant patients. Optically, it would appear that boceprevir and telaprevir are equally effective in curing treatment-resistant patients, which would be a letdown for Vertex and its investors given that expectations have clearly favored Vertex's drug over Merck's. However, Vertex allowed truly non-, or null, responders into the Realize study of telaprevir, which made it more difficult for the drug to prove efficacy. Merck, on the other hand, used a less stringent definition of null response that essentially helped boceprevir achieve a higher cure rate. If null responders are removed from analysis of the Realize study, the cure rate for partial responders and relapsers to telaprevir was 78%, which is a more accurate comparison to the 66% cure rate seen in the Merck study of boceprevir. This doesn't mean that all went swimmingly for Vertex in the Realize results. The 31% cure rate in the null responders group treated with telaprevir was lower than what Wall Street was expecting given prior results from earlier studies. Some analysts, including Bank of America's biotech analyst (and hepatitis C axe) Rachel McMinn, were expecting to see null responder cure rates for telaprevir in the 50% range. Vertex said that the null responders enrolled in the Realize study had higher rates of cirrhosis and high hepatitis C viral load than the other patients in the study, which could help explain why the cure rate among these patients was lower. Despite that, telaprevir still cured six times more null responders than re-treatment with the standard of care. Likewise, the 57% cure rate for telaprevir in partial responder patients was also a bit lower than Wall Street expectations, which means the overall, high response rate to Vertex's drug was driven largely by relapsers, considered to be the easiest of the treatment-resistant patients to respond to follow-on therapy. On the safety side of the ledger, the new telaprevir data appear to be little changed from what's been released from the previous phase III studies. Adverse events leading to patients dropping out of the study were 4% in the telaprevir arm compared to 3% in the control arm. The most common adverse events attributed to telaprevir were fatigue and rash.
Vertex intends to make a full presentation of the Realize study data at a future medical meeting or by publication in a medical journal. Both Vertex and Merck will be among the companies presenting hepatitis C drug data at the American Association for the Study of Liver Disease annual meeting at the end of October. --Written by Adam Feuerstein in Boston. >To contact the writer of this article, click here: Adam Feuerstein. >To follow the writer on Twitter, go to http://twitter.com/adamfeuerstein. >To submit a news tip, send an email to: email@example.com.