Bristol-Myers Squibb has reported data from Phase II trials of Sprycel, its developmental anticancer agent, indicating that it is effective in treating patients with leukaemia who have become resistant to first-line treatment with Novartis’ Glivec/Gleevec (imatinib).

Haematologic and cytogenetic responses were seen in some patients with CML, or Philadelphia chromosome-positive ALL, according to the company, which presented the findings at the European Haematology Association congress in Amsterdam, the Netherlands.

Sprycel (dasatanib) was recommended for approval in CML and ALL earlier this month by a US Food and Drug Administration (FDA) advisory panel, and the agency is due to deliver its verdict on the application by June 28.

Dasatanib could find a ready market in the roughly 30% of patients who do not respond to Novartis' drug, according to some analysts, who suggest the compound could see peak sales in excess of $500 million. However, clinical data showing that increasing the dose of Glivec in non-responders can also improve response rates could peg back Sprycel’s potential.

The company added that dasatanib had been filed with European regulatory authorities in January of this year, and had been granted Orphan Drug designation for Ph+ ALL and CML indications in both Europe and the USA.

The data came from four studies in which patients with various types of leukaemia were treated with 70mg of the orally-administered drug, twice a day. In the START-C study, which was an assessment of the drug as a treatment for chronic phase CML sufferers who were resistant or intolerant to imatinib, haematologic and cytogenetic responses were achieved by 90% and 51% of patients, respectively.

The START-A trial examined dasatinib in 192 imatinib-intolerant patients with accelerated phase CML, and revealed that the drug stimulated haematologic and cytogenetic response in 59% and 34% of those enrolled. Similar haematologic and cytogenetic responses were observed in both the START-B (109 myeloid blast crisis patients resistant to imatinib, 49% and 44%, respectively) and START-C (101 patients with Ph+ ALL, 49% and 22%) programmes.

There had been some concerns about dasatanib’s tolerability going into the programme, but on the whole the picture was favourable. Adverse events included Grade 3 and 4 thrombocytopenia and neutropenia, which were seen at differing levels in all the trials. Non-haematologic adverse events such as diarrhoea, headache, rash, superficial edema, pleural effusion and elevated levels of liver enzymes were also observed in some patients.