Ambit Biosciences Announces Discovery and Development Collaboration with Cephalon, Inc. Focused on Kinase Inhibitors.

SAN DIEGO -- Ambit Biosciences today announced a screening, discovery and development collaboration with Cephalon, Inc. (Nasdaq:CEPH) aimed at bringing best-in-class kinase inhibitors forward as candidates for clinical research.

By combining Ambit's proprietary KinomeScan-driven discovery capabilities with Cephalon's proven chemistry, discovery and development capabilities, the partners expect to significantly compress typical timelines for discovery and development of small molecule pharmaceutical products. Kinases constitute a large family of more than 500 related enzymes that play an important role in a broad range of human ailments, including cancer, inflammation, diabetes, infection, cardiovascular disease and central nervous system disorders.

"While they are our fourth major collaborator, Cephalon is the first pharmaceutical company to take complete advantage of Ambit's proprietary discovery platform," said Scott Salka, Chief Executive Officer of Ambit. "The cornerstone of the collaboration is Ambit's unequaled ability to screen chemical libraries across a panel of 300 kinases, which will be used to rapidly annotate Cephalon's focused library of potential kinase inhibitors."

Ambit expects to screen a large library of kinase-focused compounds obtained from Cephalon, generating nearly a million data points. The result will provide a detailed picture of how thousands of related drug-like chemical structures interact with this large family of drug targets.

"Being the first team to exploit such a rich structure-activity database should give the partnership a distinct advantage over competitors in the race to bring superior kinase inhibitors into clinical development and, ultimately, to the market," Salka added.

Cephalon will pay an up-front fee of $18 million to Ambit for access to Ambit's proprietary KinomeScan technology. In addition, the companies will collaborate on advancing two programs targeting undisclosed kinases, with Ambit having primary responsibility for delivering clinical candidates that Cephalon will further develop in exchange for additional milestone payments to Ambit of up to $232.5 million and royalties on commercial sales. Ambit will also have the opportunity to utilize Cephalon library compounds to discover and develop products that are effective inhibitors of certain undisclosed kinases.

"Our structurally diverse, proprietary chemical library of kinase inhibitors is among our most valuable assets. We see this collaboration as an opportunity to extract the maximum value from this asset in the shortest period of time," said Jeffry Vaught, Ph.D., Executive Vice President, Research & Development at Cephalon. "Ambit's technology will allow us to identify the best compounds for further research and to continue improving those we select through ongoing and iterative screening integrated tightly with our own medicinal chemistry and pharmacology efforts. Coupled to our collaborative discovery programs with Ambit, we expect to rapidly and efficiently identify drug candidates that effectively inhibit the targeted kinases while minimizing side effects due to off-target kinase modulation."

Ambit's KinomeScan technology is a new and efficient way to evaluate libraries of compounds by testing them simultaneously against a large number of human kinases. This provides information regarding how strongly the compounds bind to both intended and unintended kinases, revealing the best candidates for preclinical optimization as well as off-target interactions that could either cause unwanted side effects or reveal new indications. Additionally, the unprecedented speed of KinomeScan, which can routinely provide a three-day feedback loop between chemistry, pharmacology and screening, allows the technology to be utilized throughout the optimization process until a drug's desired kinase inhibition profile is obtained.

The KinomeScan screening platform has been featured in papers published in Nature Biotechnology and the Proceedings of the National Academy of Sciences and forms the basis of Ambit's partnerships with Roche, Bristol-Myers Squibb, GlaxoSmithKline and others.

About Kinases in Drug Development

Kinases play key roles in cancer, inflammation, diabetes and other diseases. With more than 30 kinase inhibitors in clinical trials or approved for human use including Gleevec[R], TARCEVA[R] and SUTENT[R], this important class of proteins is a rich area for drug development. However, kinases share similarities that make them difficult to target specifically, and off-target inhibition can result in side effects or toxicity.

About KinomeScan

KinomeScan is a platform that employs an ATP-site dependent competition binding assay using Ambit's proprietary amplifiable fusion protein (AFP[TM]) system. Through AFP, kinases of interest are fused to an Ambit-proprietary bacteriophage, which facilitates enzyme production, isolation and quantitation. Client libraries remain confidential and chemical structures are not required to utilize KinomeScan. This simple, highly efficient approach ensures discovery programs stay on an optimal development course, provides unprecedented insight into how molecules or entire libraries bind to both intended and unintended kinases, and opportunistically identifies unanticipated interactions that can expand the therapeutic utility of compounds or serve as advanced starting points for new programs.

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. Ambit plans to initiate clinical trials in 2006 for AC220, its selective class III receptor tyrosine kinase inhibitor that will initially be tested in patients with acute myeloid leukemia. Ambit's proprietary kinase profiling technology, KinomeScan, is designed to be integrated across all stages of the drug discovery and development process and has been validated through collaborations with Roche, Bristol-Myers Squibb Company, GlaxoSmithKline and others. Ambit has a strong syndicate of investors including Perseus-Soros Biopharmaceutical Fund, Forward Ventures, Roche Venture Fund, Avalon Ventures, GIMV NV, MDS Capital, Genechem and Bristol-Myers Squibb Company.

Gleevec[R] is a registered trademark of Novartis Pharmaceuticals Corporation. TARCEVA[R] is a registered trademark of OSI Pharmaceuticals, Inc. SUTENT[R] is a registered trademark of Pfizer, Inc.