Vestar Inc. on Wednesday announced plans to develop ageneric version of taxol under a joint venture agreement withthe Canadian pharmaceutical company Towers PhytochemicalLtd.
Parallel with its development of a generic version of BristolMyers-Squibb's paclitaxel, Vestar also will pursue a liposomalformulation. The company will initially market taxol in Canadaand other international markets.
Towers Phytochemical of Richmond, British Columbia, wasfounded in 1990 to conduct research, development andcommercialization of natural products, particularly taxol. Thecompany received a repayable loan from the Canadiangovernment for C$3.5 million (U.S.$2.66 million at Wednesday'sexchange rate) with the understanding that Towers wouldbuild a plant to develop taxol and that Canadians would havepriority in obtaining the drug. A commercial facility is underconstruction in the Vancouver area.
Towers has long-term, exclusive agreements with severalforest product companies in British Columbia to harvest thePacific yew.
Towers is also pursuing alternative sources of taxol, includingbark from species other than the Pacific yew.
Under its 50-50 venture with Vestar, Towers will extract taxolfrom the bark of the Pacific yew and Vestar will develop,manufacture and market all taxol products. Terms of theagreement were not disclosed.
Michael Hart, Vestar's chief financial officer, said the companyhad been interested in developing a taxol product but wasdeterred by the limited supply of Pacific yews, currently theonly source of taxol.
The joint venture with Towers provides Vestar with a long-term, exclusive source of taxol and "the immediate opportunityto pursue a generic version," Hart said. Taxol is approved onlyin the U.S. and Canada, and no generic version is on the market.Since taxol is not patented, any company that can get a supplyof the drug and prove that its formulation is bioequivalent toBristol's product can market it.
Hart noted that in addition to developing a liposomalformulation, Vestar also may use its pro-drug technology,which enables oral delivery of chemotherapeutics.
Vestar and Towers join a growing list of companies in the taxolsweepstakes. With a market potential projected to reach ashigh as $1 billion, companies are looking at a variety of ways tosynthesize this compound.
One intriguing possibility is the use of a fungus to produce anendless supply of taxol. This approach is being pursued byCytocolonal Pharmaceutics Inc. of Dallas. The company recentlyobtained an exclusive license from the Research andDevelopment Institute of Bozeman, Montana, which licensestechnologies on behalf of Montana State University (MSU), todevelop a fungus for taxol production.
Andrea Stierle, a researcher at MSU, discovered the fungusgrowing on a single Pacific yew tree in Montana, and she andcolleague Gary Strobel found that it produced low levels oftaxol (see BioWorld, April 9).
Arthur Bollon, chairman and chief executive officer ofCytoclonal, said the company is working in two areas to boostthe production of taxol from the fungus: metabolic inductionand genetic engineering. The latter approach has just beeninitiated, while the first technique has "dramatically improvedlevels of taxol," Bollon said. He contended that "nothing will beable to compete with fungal production" of the compound, as itis "the most cost-effective approach there is."
The company also has an R&D contract with MSU to developother taxanes that have been shown to exist in the fungus andmay have better activity.
Cytoclonal won the licensing agreement over 12 other bidders,including Bristol Myers-Squibb, Lederle and Escagenetics Corp.Cytoclonal was selected because it has an established programin genetic engineering of fungi. Bollon noted that the companyhas produced necrosis factor, interferon and cytokines in fungi.
-- Brenda Sandburg News Editor
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