Pfizer has selected R343, a novel small-molecule drug candidate of Rigel Pharmaceuticals, for advanced preclinical development in allergic asthma. Rigel will receive a $5 million milestone payment from Pfizer. The collaboration was established in 2005 and aims to investigate and develop syk kinase inhibitors via intrapulmonary delivery to find treatments for allergic asthma and chronic obstructive pulmonary disease.

Under the terms of the agreement, Rigel received an initial cash payment and is eligible to receive milestone payments for preclinical and clinical events as well as royalties on any future product sales. Pfizer made an equity investment in Rigel and is responsible for worldwide development and commercialization of any resulting compounds. Additional terms were not disclosed.

"Pfizer's decision to take R343 into development is significant because it supports the potential of syk inhibition in the treatment of allergic diseases such as allergic asthma," Donald G. Payan, executive VP and chief scientific officer of Rigel said adding, "It is also significant because Pfizer is committing substantial investment and scientific resources ahead of the clinical development of this new treatment approach."

R343 is designed to block the major pathways that are triggered in allergic asthma. It appears to be particularly appropriate for intrapulmonary delivery due to its limited systemic exposure, according to the company release.

Syk kinase is a protein tyrosine kinase that plays a pivotal role in high affinity IgE receptor signaling in mast cells. Rigel's syk kinase inhibitors are designed to bind to syk in mast cells and interrupt the signal from the IgE receptor, thus preventing cellular activation and subsequent chemical mediator release, and potentially blocking an allergic response in allergic asthma.