Exelixis thus retains full rights to five of the six candidates developed with GSK.

GlaxoSmithKline will not exercise its option to select a second candidate for development from its collaboration with Exelixis. The conclusion of this partnership sent Exelixis’ shares down 11% to open the day at $4.

The collaboration, which began in 2002 with a focus on vascular biology, inflammatory disease, and oncology, yielded six compounds. GSK had the right to choose two but has decided to continue with the one already in-licensed anticancer agent, XL880. As GSK continues development on XL880, Exelixis will receive milestones of up to $90 million and double-digit royalties.

Exelixis thus now owns full rights to the remaining five molecules, with XL184 being the furthest along. It is in various stages of clinical development for medullary thyroid cancer (MTC), non-small-cell lung cancer, and glioblastoma. Exelixis will pay GSK a 3% royalty on net sales of any product incorporating XL184.

In relation to XL184, president and CEO of Exelixis, George A. Scangos, Ph.D., says, “We have had a significant number of inquiries about our willingness to partner the program, and we are exploring all options to advance the program and maximize its value to the company.”

“We are pleased to retain the rights to develop and commercialize XL184,” Dr. Scangos continues. “This compound is our most advanced asset with a promising mechanism of action. It has generated compelling data in patients with medullary thyroid cancer, and data emerging from the Phase II trial being conducted in patients with glioblastoma also are encouraging. We recently initiated a Phase III registration trial for XL184 in MTC, and we look forward to the successful progress of this and other trials for the compound.”

The other four compounds are XL281, a Phase I candidate for solid tumors; XL228, in early-stage trials for leukemia and advanced malignancies; XL820, which is in Phase I for gastrointestinal stromal cancer; and XL844, in Phase I for advance solid tumors

“These compounds, together with the compounds already in Exelixis’ clinical pipeline, XL147, XL765, XL019, and XL888, comprise a deep pipeline of promising oncology compounds,” notes Dr. Scangos. “The clarity achieved through the expiration of the collaboration will allow Exelixis to further define its clinical, commercial, and financial strategies, which will become apparent over the next few months.”

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