The US Food and Drug Administration (FDA) has accepted Pfizer Inc.'s  New Drug Application (NDA) for standard review of bosutinib as a treatment option for adult patients with previously treated Philadelphia chromosome positive (Ph+) chronic myeloid leukaemia (CML). This submission was based on efficacy and safety data from Study 200, a single-arm study of bosutinib in over 500 patients with previously treated Ph+ CML, including patients resistant or intolerant to imatinib as well as patients who were previously treated with dasatinib or nilotinib. Currently, there are no approved therapies available for CML patients after second-line treatment with dasatinib or nilotinib.

CML, one of the four main types of leukaemia, accounts for 15 per cent of all leukaemias worldwide. Despite the availability of existing treatments, there remains a need for additional options for CML patients, given observed treatment–related toxicities and resistance.

“This filing underscores our commitment to bringing innovative treatment options to haematologic patient populations like CML, where the need for additional treatment options exists,” said Garry Nicholson, president and general manager of the Pfizer Oncology Business Unit. “We are excited about the potential to bring this promising agent to those patients who fail or progress on previous therapies.”

Bosutinib is an oral, once-daily, investigational dual Src and Abl kinase inhibitor with minimal inhibitory activity against c-kit and PDGFR. It is believed that, by dual inhibition of the Src and Abl tyrosine kinases, bosutinib may inhibit signalling in CML cells that allows the cells to grow, survive and reproduce.

A hallmark of CML is an abnormal chromosome known as the Philadelphia chromosome, a DNA mutation that initiates a series of events leading to the development of Bcr-Abl, a tyrosine kinase that causes CML cells to grow and reproduce rapidly. In some cases, resistance may develop to currently available therapies that inhibit Bcr-Abl. Inhibition of both Src and Abl tyrosine kinases may help overcome this resistance, as overexpression of the Src family of tyrosine kinases has been implicated in resistance and CML progression.

Haematologic cancers are a complex group of diseases, with over 70 different types of lymphomas, leukaemias or myelomas. While there have been significant advancements in the treatment of some haematologic cancers, there continues to be a need for additional therapeutic options. Pfizer Oncology is committed to improving outcomes for patients living with haematologic malignancies like CML. Pfizer Oncology has a robust haematology pipeline, with biologics and small molecules in clinical development across a number of haematologic malignancies. We are advancing technologies as well as working to identify new and innovative options that address specific haematologic cancers, molecular subtypes, gene over-expression and mechanisms of resistance.

Pfizer Oncology is committed to the discovery, investigation and development of innovative treatment options to improve the outlook for cancer patients worldwide.