SAN DIEGO, Dec. 7 /PRNewswire/ -- Ambit Biosciences Corporation announced today the presentation of two posters presenting the results of preclinical studies evaluating AC220 at the 51st Annual Meeting of the American Society of Hematology (ASH) in New Orleans. AC220, Ambit's lead product candidate, is a novel, orally available, small molecule that was expressly optimized as a FMS-like tyrosine kinase-3 (FLT3) inhibitor for the treatment of AML. Ambit has completed enrollment of patients in the first-in-human Phase 1 clinical trial in relapsed/refractory AML. A summary of the posters are as follows:

- "AC220, a FLT3 Inhibitor, Increases Survival in Two Genotypically
  Distinct FLT3 ITD Models of Acute Myeloid Leukemia and Provides
  Sustained Protection Following Chronic Administration"

  The study examined the in vivo efficacy of AC220 in limited versus
  chronic dosing regimens in:

  (i)  an AML disease model dependent on homozygous mutations of the
        internal tandem duplication (ITD) mutation of FLT3, or FLT3 ITD,
        (MV4-11 disseminated mouse disease model), and
  (ii) a separate model that is heterozygous for the FLT3 ITD mutation
        and whose AML disease progression is believed to be in part
        driven by genetic mutations unrelated to FLT3 (MOLM-14 disease
        model)

  The second model was included to increase the rigor of the preclinical
  assessment of AC220's in vivo efficacy, as AML is a heterogeneous
  disease and in a clinical setting is believed to be seldom driven by
  FLT3 ITD mutations alone.  Results of these experiments suggest that
  AC220 is efficacious in disease models driven by both FLT3 ITD
  homozygous and heterozygous genotypes.  These experiments also concluded
  that chronic dosing may provide greater disease protection than a
  limited course of therapy as demonstrated by prolonged survival
  correlated with delayed disease onset in both disease models.  The
  results of this preclinical study are consistent with observations of
  AML patients treated with intermittent versus continuous dosing
  schedules of AC220 in a Phase 1 clinical study.

- "AC220, a Potent and Specific FLT3 Inhibitor, Enhances the Cytotoxic
  Effects of Chemotherapeutic Agents in Cell Culture and in Mouse Tumor
  Xenograft Models"

  Patients with FLT3 ITD mutations generally have a poorer prognosis and
  decreased response to standard chemotherapy treatments compared to
  patients without the mutation.  A series of in vitro cell-based
  experiments assessed the effects of AC220 dosed in combination with a
  variety of different chemotherapeutic agents (including cytarabine,
  decitabine, cladribine, etoposide, and daunorubicin) and in a variety of
  different dosing schedules.  The studies collectively and consistently
  demonstrated that whether AC220 is dosed prior to, concurrently with, or
  subsequent to the dosing of the individual chemotherapeutic that it
  generally provided additive to slightly synergistic effects compared to
  dosing of either drug alone.  These findings were replicated in an in
  vivo setting with studies evaluating AC220 in combination with
  cytarabine or decitabine.  Not only did these experiments confirm the in
  vitro findings by evidence of additive effects on reducing tumor burden,
  significantly extending time-to-endpoint, increasing remission rates,
  and in some cases achieving cures, but there was also no indication of
  drug specific antagonism on tumor volume, body weight or WBC counts for
  any of the dosing schedules.  These results support the clinical
  investigation of AC220 in combination with chemotherapy in AML.

"Combined, these posters present a comprehensive and compelling picture that illustrates the preclinical efficacy of AC220 in a range of AML disease models driven by FLT3 ITD mutations and in combination with a variety of chemotherapy agents commonly used to treat AML," said Wendell Wierenga, PhD, Executive Vice President, Research & Development at Ambit. "Not only do these findings support the continued investigation of AC220 as monotherapy in AML patients that harbor the FLT3 ITD mutation, but these results also provide insights on a range of plausible considerations for the design and conduct of clinical trials that combine the targeted therapy, AC220, with chemotherapy in the treatment of AML patients. We look forward to expanding our clinical program to include such trials in the future."

About AC220

AC220, Ambit's lead product candidate, is a novel, potent, highly selective, orally bioavailable second-generation FLT3 inhibitor currently under evaluation as a monotherapy treatment in adult patients with relapsed/refractory acute myeloid leukemia (AML). AML is the most common type of blood cancer in adults, and the kinase FLT3 is mutated and constitutively activated in 25-40 percent of such patients. FLT3 ITD mutations predict poor prognosis and decreased response to existing treatments, including chemotherapy and hematopoietic stem cell transplant. Ambit leveraged KINOMEscan(TM), the company's proprietary, high-throughput method for screening small molecule compounds against a large number of human kinases, to advance AC220 from concept to lead candidate selection in only 18 months.

About Acute Myeloid Leukemia (AML)

Acute myeloid leukemia is a form of blood cancer. According to the American Cancer Society, approximately 13,000 new cases of AML will be diagnosed in the United States in 2008. The median age of a patient with AML is about 67 years. Standard treatment for patients 60 years or older with AML includes systemic combination chemotherapy. The median survival for patients receiving induction chemotherapy, which is associated with high mortality, is 6-11 months, with shorter survival for patients over the age of 60 years. The five-year survival rate for AML is less than 15 percent due to refractory and relapsed disease associated with standard treatments. According to a report from Decision Resources, the U.S. AML market is expected to more than double by 2015.

About Ambit Biosciences

Ambit Biosciences is a privately-held biopharmaceutical company engaged in the discovery and development of small molecule kinase inhibitors for the treatment of cancer, inflammatory disease, and other indications. Ambit employs a novel and proprietary kinase profiling technology, KINOMEscan(TM), to screen compounds against 442 human kinases.

Ambit's lead compound, AC220, is in clinical development for the treatment of AML and other indications. Ambit plans to commence in 2009 and 2010 several clinical studies with AC220, including a registration study in AML. Ambit's clinical pipeline also includes AC480, an oral pan-HER inhibitor that was in-licensed from BMS. Ambit is conducting Phase 2 studies with AC480 in patients with solid tumor cancers. Additionally, Ambit has an advancing pool of preclinical candidates targeting BRAF (in collaboration with Cephalon), JAK2, Aurora, and CSF1R. Through its KINOMEscan Division, Ambit markets its technology as a profiling service. For more information, visit www.ambitbio.com.

Contact:

M. Scott Salka           Scott Lerman
Ambit Biosciences        The Ruth Group
(858) 334-2101           (917) 324-1719 (on-site at ASH)
                         (646) 536-7013 (office)
                         slerman@theruthgroup.com

SOURCE Ambit Biosciences Corporation

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