Data from Phase 2 ACE Study (AMBI) of Quizartinib in Refractory Acute Myeloid Leukemia

SAN DIEGO, June 26, 2013 /PRNewswire/ — Ambit Biosciences Corporation (Nasdaq: AMBI) announced today data from the Phase 2 ACE study of quizartinib (AC220), a FLT3 inhibitor, were featured in multiple presentations at the 18^th Congress of the European Hematology Association in Stockholm, Sweden.

Data presented included analyses of patients with relapsed or refractory acute myeloid leukemia (AML) from a Phase 2 clinical trial of quizartinib as monotherapy. In the study, quizartinib was administered orally, once a day, in 28-day treatment cycles until disease progression, elective hematopoietic stem cell transplantation (HSCT) or unacceptable toxicity. Based on the positive data from the Phase 2 clinical trial, as well as ongoing discussions with the Food and Drug Administration (FDA), Ambit is planning to initiate a Phase 3 clinical trial in FLT3-ITD positive patients with relapsed or refractory AML in early 2014.

Data Presentations

High Response Rate and Bridging to Hematopoietic Stem Cell Transplantation With Quizartinib (AC220) in Patients With FLT3-ITD– Positive Relapsed/Refractory Acute Myeloid Leukemia (AML)
Mark J. Levis, M.D., Ph.D., Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Md.

Data from 136 FLT3-ITD positive patients, aged 18 years or older, with either relapsed disease or who were refractory to second-line chemotherapy or HSCT, were presented. Of the patients treated, 35 percent were successfully bridged to a potentially curative HSCT, with the greatest proportion receiving a HSCT after achieving a CRi (complete remission with incomplete hematologic recovery) with quizartinib. Additionally, 33 percent of patients who were bridged to HCST after achieving a CRi were still alive after one year, with multiple patients alive after more than two years.

Additional key findings presented include:

• Forty-six percent of FLT3-ITD positive patients achieved a composite complete response (CRc: complete remission (CR) + complete remission with incomplete platelet recovery (CRp) + complete remission with incomplete hematologic recovery (CRi)), including five percent of patients who achieved either a CR or CRp
• Median overall survival for the 47 FLT3-ITD positive patients who were bridged to a subsequent HSCT was 34.1 weeks, compared to 24.1 weeks for the 56 patients who achieved either a CRc or PR but did not undergo a subsequent  HSCT
• Median overall survival for the 33 FLT3-ITD positive patients who did not achieve at least a PR to quizartinib and did not undergo a subsequent HSCT was 8.9 weeks
• Twenty percent (27/136) FLT3-ITD positive patients remained alive for more than 12 months and were classified as long-term survivors
• All but one of the long-term survivors achieved at least a PR to quizartinib, with 63 percent (17/27) proceeding to a HSCT after quizartinib
• Ten of the 27 long-term survivors did not undergo a subsequent HSCT and had a median treatment duration of 53.5 weeks
• Quizartinib was generally well tolerated with manageable toxicity which included a grade 3 QTcF prolongation of 20 percent and no grade 4 QTcF prolongation events

Efficacy and Safety of Quizartinib (AC220) in Patients Age ≥60 Years with FLT3-ITD Positive Relapsed/Refractory Acute Myeloid Leukemia (AML)
Hartmut Dohner, M.D., Department of Internal Medicine III, University Hospital of Ulm, Ulm, Germany

Data from 110 FLT3-ITD positive patients, aged 60 years or older, who relapsed within one year or were refractory to first-line therapy were presented. Of the patients treated, 57 percent achieved a CRc, with seven percent having either a CR or CRp, with a median survival of 25.3 weeks. Additionally, 16 patients (15 percent) remained alive for more than 12 months and were classified as long-term survivors.

Additional key findings presented include:

• Of the 104 FLT3-ITD positive patients who lived at least 28 days to be assessed for response, the median overall survival for the 84 patients who achieved either a CRc or partial response (PR) to quizartinib is  31.1 weeks, compared to 11.8 weeks for the 20 patients who did not achieve at least a PR to quizartinib
• Median overall survival was 25.3 weeks for all patients, with a median of 22.7 weeks for patients age 70 years or older
• All patients who were long-term survivors achieved either a CRc or PR to quizartinib, with 52.1 weeks as median duration of treatment
• Quizartinib was generally well tolerated, with a 30-day mortality rate of five percent

About Quizartinib
Quizartinib (AC220) is a novel, potent, highly selective, orally bioavailable FMS-like tyrosine kinase-3 (FLT3) inhibitor currently under evaluation in multiple ongoing studies, which include a Phase 2b clinical trial as monotherapy treatment for adult patients with FLT3-ITD positive relapsed or refractory AML and two Phase 1 studies in a combination treatment regimen with chemotherapy, and as a maintenance therapy following transplant, respectively.

On March 12, 2013, Ambit and Astellas Pharma Inc., announced that their collaboration for the joint development and commercialization of quizartinib will terminate effective September 3, 2013, at which time Ambit will exclusively own worldwide rights to quizartinib and any follow-on compounds.  The companies are working on the transition of the current development activities to Ambit.

About Ambit Biosciences
Ambit is a biopharmaceutical company focused on the discovery, development and commercialization of drugs to treat unmet medical needs in oncology, autoimmune and inflammatory diseases by inhibiting kinases that are important drivers for those diseases. Ambit’s lead drug candidate, quizartinib (AC220), is a once-daily, orally-administered potent and selective, inhibitor of FMS-like tyrosine kinase-3 (FLT3) and is currently under clinical development in patients with relapsed/refractory acute myeloid leukemia (AML) and in newly diagnosed AML patients in combination with chemotherapy as well as maintenance following a hematopoietic stem cell transplantation (HSCT). In addition to quizartinib, Ambit’s clinical pipeline includes AC410, an oral JAK2 inhibitor, and CEP-32496, a BRAF inhibitor licensed to Teva Pharmaceutical Industries Ltd. Ambit’s preclinical portfolio includes a proprietary CSF1R inhibitor program.

Forward-Looking Statements
Statements contained in this press release regarding matters that are not historical facts are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, including statements associated with Ambit’s expectations regarding future development and therapeutic potential of Ambit’s lead drug candidate and other programs. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements. Words such as “believes,” “anticipates,” “plans,” “expects,” “intends,” “will,” “goal,” “potential” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon Ambit’s current expectations and involve assumptions that may never materialize or may prove to be incorrect. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of various risks and uncertainties, which include, without limitation, risks associated with the process of discovering, developing and commercializing drugs that are safe and effective for use as human therapeutics, and in the endeavor of building a business around such drugs. These and other risks concerning Ambit’s programs are described in additional detail in Ambit’s SEC filings. All forward-looking statements contained in this press release speak only as of the date on which they were made. Ambit undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made.

Contacts:

Ian Stone or David Schull (Media)
Russo Partners
(619) 308-6541
(212) 845-4271
ian.stone@russopartnersllc.com
david.schull@russopartnersllc.com

Robert Flamm, Ph.D. (Investor)
Russo Partners
(212) 845-4226
robert.flamm@russopartnersllc.com