Ambit Biosciences Announces Presentation of Results From Phase 2 ACE Study of Quizartinib in Patients With Relapsed or Refractory Acute Myeloid Leukemia (AML) at the Annual Meeting of the American Society of Clinical Oncology

CHICAGO, June 4, 2013 /PRNewswire/ -- Ambit Biosciences Corporation (Nasdaq: AMBI) announced today that multiple presentations from the Phase 2 ACE study of quizartinib (AC220), a FLT3 inhibitor, were presented at the Annual Meeting of the American Society of Clinical Oncology.

Data presented included analyses of the 333 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 FLT3ITD Positive or Negative Relapsed/Refractory AML after Second Line Chemotherapy or Previous Bone Marrow Transplant (Abstract #7012)
Jorge Cortes, M.D., Division of Cancer Medicine, The University of Texas M. D. Anderson Cancer Center, Houston, Texas

Data from 176 patients, aged 18 years or older, with either relapsed disease or who were refractory to second-line chemotherapy or HSCT were presented. Of the 136 FLT3 positive patients, 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 achieved either a CRc or partial response (PR) to quizartinib and 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, highlighting the positive impact of bridge to HSCT
• Median overall survival for the 33 FLT3-ITD positive patients who did not achieve at least a PR to quizartinib was 8.9 weeks, which reflects the limited therapeutic options these patients have in this setting and the importance of achieving a response to quizartinib given its positive impact on overall survival
• 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
• Additionally, 30 percent of FLT3-ITD negative patients achieved a CRc, including six percent who achieved either a CR or CRp to quizartinib highlighting this as an area of continued clinical development for quizartinib
• Quizartinib was generally well tolerated with manageable toxicity which included a grade 3 QTcF prolongation of 18 percent and no grade 4 QTcF prolongation events

Quizartinib (AC220) Produces High Response Rates and Long-Term Survival in Elderly Patients With FLT3-ITD(+) or FLT3-ITD() Relapsed/Refractory Acute Myeloid Leukemi
Giovanni Martinelli, M.D., Ph.D., Seragnoli Institute of Hematology, University of Bologna School of Medicine, Bologna, Italy

Data presented included response rates and long-term survival in 154 patients, aged 60 years or older, who had relapsed within one year or were refractory to first-line therapy. Of the 110 FLT3-ITD positive patients, 57 percent achieved a CRc, with seven percent having either a CR or CRp, with a median survival of 25.3 weeks. Additionally, 14 percent of patients remained alive for more than 12 months and were classified as long-term survivors which highlights the clinical benefit of quizartinib given all patients in this analysis were 60 years of age or older, with nearly 50 percent refractory to their last therapy and overall had a poor prognosis.

Additional key findings presented include:

• Of the 104 FLT3-ITD positive patients who lived at least 28 days to be assessed for response (excludes six patients from the intent-to-treat population), 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
• Of the 14 percent (22/154) of patients who were long-term survivors, 95 percent achieved either a CRc or PR to quizartinib, with 52.1 weeks as median duration of treatment for the 16/110 FLT3-ITD positive patients who were long-term survivors, which further highlights the long treatment duration in this patient population
• Additionally 36 percent of FLT3-ITD negative patients achieved a CRc, with seven percent achieving either a CR or CRp with quizartinib, and their median survival was 19.1 weeks
• Quizartinib was generally well tolerated, with a 30-day mortality rate of six percent

Efficacy and Safety of Quizartinib (AC220) in Patients Aged 70 Years With FLT3ITD(+)or FLT3ITD() Relapsed/Refractory Acute Myeloid Leukemia
Alexander Perl, M.D., Division of Hematology/Oncology, University of Pennsylvania, Philadelphia, Penn.

Data presented in 83 patients, aged 70 years or older, who had relapsed or were refractory to their last therapy supported high response rates with quizartinib similar to that seen in younger treated patient populations in the study, despite the generally higher level of heterogeneity seen in elderly patients with AML. Of the 60 FLT3-ITD positive patients, 53 percent achieved a CRc, with 7 percent having either a CR or CRp. The median survival for these patients was 21 weeks. Additionally, 14 percent (12/83) of patients remained alive for more than 12 months, the majority of which (8/12) were FLT3-ITD positive, and were classified as long-term survivors. The eight FLT3-ITD positive long-term survivors all achieved at least a PR to quizartinib and remained on treatment for a median of 53 weeks with survival ranging up to 93+ weeks.

Additional key findings presented include:

• Additionally 43 percent of FLT3-ITD negative patients achieved a CRc, with 13 percent achieving either a CR or CRp with quizartinib, and had a median survival of 19 weeks
• Quizartinib was generally well-tolerated, with a 30-day mortality rate of eight 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

SOURCE Ambit Biosciences Corporation