Bristol-Myers Squibb’s cancer drug Sprycel, intended to treat leukaemias that are resistant to Novartis’ Gleevec, is due to come in front of a US Food and Drug Administration advisory committee on June 2.

Sprycel (dasatinib) was filed for approval in the USA in December 2005 as a treatment for chronic myelogenous leukemia, as well as Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia, in adult patients with resistance or intolerance to prior therapy, including Gleevec (imatinib). It has been fast-tracked for approval by the FDA and the agency is due to deliver a verdict on the application by June 28.

The application is based on Phase II data from 1,000 Gleevec-resistant or intolerant patient with CML, reported last year at the American Society of Hematology annual meeting which showed that dasatinib achieved complete a cytogenetic response in 97% of Gleevec-resistant or intolerant chronic-phase CML patients.

However, the FDA's oncologic advisory committee said it will have to determine whether these Phase II data are enough to predict a clinical benefit for Sprycel, such as prolonged survival in patients with CML. B-MS believes Sprycel has a greater preclinical potency than Gleevec and estimates that 15-20% of patients treated for CML do not achieve major cytogenetic responses to Gleevec within the first 12 months and that 5-10% develop resistance.

Dasatanib could find a ready market in the roughly 30% of patients who do not respond to Novartis' drug, according to analysts, who suggest the compound could see peak sales in excess of $500 million.