Tokyo-based Astellas Pharma and San Diego-based Ambit Biosciences will end their collaboration for the joint development and commercialization of FMS-like tyrosine kinase-3 (FLT3) inhibitors, including quizartinib, effective September 3, 2013.

Astellas has exercised its right to terminate the worldwide license agreement signed in 2009, and over the months ahead the companies will work together to transfer current development activities to Ambit. Upon the effective date of termination, Ambit will regain all rights granted to Astellas and continue with the quizartinib clinical trial program. The termination of the collaboration came just days after Ambit Biosciences announced its second attempt at an IPO.

"While our decision is based on strategic reasons, we are proud of our collaborative work with Ambit, and we are committed to working with Ambit on a smooth transition," said Yoshihiko Hatanaka, president and CEO of Astellas. "We remain committed to the field of oncology as a major area of focus for the company and will continue to pursue our goal of becoming a global category leader in oncology."

Michael Martino, president and CEO of Ambit, said, "With the phase II study results for quizartinib that were presented at the ASH Annual Meeting last December, we and members of the medical community continue to be excited about quizartinib and its potential to meet a significant, unmet need in acute myeloid leukemia (AML) patients. We are fully committed to moving forward with the phase III clinical trial plan and look forward to advancing this important drug candidate toward approval."

Quizartinib (AC220) is a novel, potent, highly selective, orally bioavailable FMS-like tyrosine kinase-3 (FLT3) inhibitor currently under evaluation in a phase IIb clinical trial as monotherapy treatment for adult patients with relapsed or refractory AML, and in two phase I studies in a combination treatment regimen with chemotherapy, and as a maintenance therapy following transplant, respectively.