( HAYWARD Calif. April 18 2007 /PRNew...)Kosan Presents Preclinical Data on Nuclear Export Inhibitors, Novel,Anticancer Agents, at AACR,Health

HAYWARD, Calif., April 18, 2007 /PRNewswire-FirstCall/ -- Kosan Biosciences Incorporated today presented preclinical data on its proprietary nuclear export inhibitors (NEI) showing induction of potent, fast-acting and long-lasting anticancer activity with a high degree of tolerability in multiple human tumor xenograft cancer models.

Kosan's NEIs are potent, specific inhibitors of CRM1, a highly conserved, essential protein that exports key regulatory proteins ("cargo" proteins) from the nucleus to the cytoplasm. Many cargo proteins that depend on CRM1 for nuclear export, such as p53, Bcr-Abl and FOXO-3a, function as tumor suppressors or transcription factors that protect normal cells by regulating cell growth and apoptosis (cell death). Accumulation of these CRM1 cargo proteins in the nucleus, by blocking nuclear export, leads to the inhibition of cell growth and apoptosis selectively in cancer cells. Kosan's polyketide- based NEI compounds have optimized pharmaceutical properties, including potency, durability of action and a wide therapeutic index. Kosan anticipates becoming the first company to advance a nuclear export inhibitor into clinical development.

"We believe that Kosan has established an industry-leading position in NEI technology and has the only NEI inhibitor in late-stage preclinical development," said Pieter B.M.W.M. Timmermans, Ph.D., Kosan's Senior Vice President, Drug Discovery and Preclinical Development. "Our NEIs have demonstrated potent anticancer activity in human tumor xenograft models of breast, cervical, colon and non-small cell lung cancers, melanoma and leukemia, and have been shown to have robust efficacy in vivo at doses that are well-tolerated. We believe that NEIs represent a novel mechanism of action and have the potential to work additively and synergistically with a broad spectrum of cancer chemotherapies such as DNA-damaging agents that have limited durability
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