GlaxoSmithKline (GSK) has informed Cytokinetics, Incorporated that it will not exercise its option to license ispinesib or SB-743921 as provided under the Collaboration and License Agreement entered into by the companies in 2001. All rights to ispinesib and SB-743921, each novel inhibitors of kinesin spindle protein (KSP), will revert to Cytokinetics, on agreed terms. The collaboration between Cytokinetics and GSK will continue, and will be focused on the development by GSK of GSK-923295, an inhibitor of centromere-associated protein-E (CENP-E).

"The seven year collaboration between Cytokinetics and GSK has generated three novel drug candidates now in clinical development," said Paolo Paoletti, senior vice president of GSK Oncology R&D. "The decision by GSK to not exercise options on ispinesib and SB-743921 was the result of a shift in portfolio direction for GSK. We continue to believe that the novel mechanism of anti-mitotics may bring hope to cancer patients, reflected in GSK's ongoing development of GSK-923295 under its collaboration with Cytokinetics."

"While we are disappointed in this outcome, we understand GSK's business decision. We are encouraged by the safety and tolerability of each of ispinesib and SB-743921 as well as the amplified activity observed with the more dose-dense scheduling of these novel drug candidates," stated Robert I. Blum, Cytokinetics' president and chief executive officer. "We are committed to advancing these two drug candidates through to the end of Phase I and will then evaluate the next steps for ispinesiband SB-743921 in context of the results, required funding and other partnering possibilities."

In June 2001, Cytokinetics and GSK entered into a broad strategic alliance to discover, develop and commercialize novel small molecule therapeutics targeting mitotic kinesins for applications in the treatment of cancer and other diseases. The strategic alliance has generated three drug candidates in clinical development, ispinesib and SB-743921, both inhibitors of KSP, and GSK-923295, an inhibitor of CENP-E. Under a November 2006 amendment to its collaboration and license agreement with GSK, Cytokinetics assumed responsibility for the costs and activities associated with the continued development of ispinesib and SB-743921, subject to GSK's option to resume responsibility for some or all development and commercialization activities associated with each of these novel drug candidates, exercisable during a defined period.

With this announcement, Cytokinetics will proceed, independent of GSK, with the further development of ispinesib and SB-743921 subject to agreed terms. GSK-923295, now in a phase-I clinical trial in advanced cancers, is being developed under the strategic alliance by GSK. In June 2008, Cytokinetics announced a further one-year extension of the strategic alliance's research term to continue activities focused towards translational research directed to CENP-E. Each company will receive royalties from the sale of any products arising from the strategic alliance that the other company progresses to commercialization. For products that GSK progresses in development, Cytokinetics retains a product-by-product option to co-fund certain later-stage development activities, thereby providing Cytokinetics an opportunity to increase its potential royalties and obtain co-promotion rights in North America.