Rigel is eligible to over $1 billion in milestones related to this oral Syk inhibitor, poised to enter Phase III trials.

Rigel Pharmaceuticals will earn $100 million up front as part of an exclusive, global agreement with AstraZeneca covering the late-stage rheumatoid arthritis (RA) candidate R788 (fostamatinib disodium). The deal gives AstraZeneca exclusive rights to develop and commercialize the oral spleen tyrosine kinase (Syk) inhibitor in RA and additional indications. AstraZeneca will also have exclusive rights to Rigel’s pipeline of oral Syk inhibitors.

Rigel could earn an additional $345 million in development, regulatory, and initial sales milestones plus another $800 million in specified sales-related milestones and double-digit sales royalties.

Rigel has already completed Phase II development of R788 for the RA indication. The company has also taken the candidate into Phase II trials as a treatment for immune thrombocytopenic purpura, B-cell lymphoma, and T-cell lymphoma.

AstraZeneca will be responsible for a global Phase III program in RA, which it anticipates starting during the second half of this year. The company will also take over all regulatory, manufacturing, and global commercialization activities for its licensed indications. First regulatory filings with FDA and European authorities are projected for 2013.

Fostamatinib disodium is being developed primarily as a next generation oral RA therapy in adults who have failed to respond adequately to a traditional disease modifying anti-rheumatic drug such as methotrexate and where a TNF biologic add-on treatment would be considered. The compound is believed to act by blocking the intracellular signaling of immune cells implicated in the destruction of bone and cartilage, Rigel states.

In July 2009, the company reported results from a Phase IIb study showing significant improvement in RA patients treated with R788 who had failed to respond to methotrexate treatment. Results from another study evaluating patients who had failed to respond to at least one biologic treatment such as TNF inhibitors treated with R788 did not demonstrate a response that was higher than placebo by a statistically significant margin in the primary and secondary endpoints.

Rigel has separately partnered with Pfizer for the development of another Syk inhibitor, R343, for the inhaled treatment of allergic asthma. Pfizer initiated a Phase Ib trial with R343 in the second quarter of 2009. A Phase II trial is expected to start in 2010, Rigel notes.

The firm’s lead oncology product, R763, is a small molecule inhibitor of aurora kinase. The program is partnered with Merck Serono, which has exclusive rights to the drug and has initiated Phase I trials. 

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