Pfizer has extended its research collaboration with Ligand Pharmaceuticals for JAK3, an important therapeutic target to treat autoimmune disorders, inflammation and organ transplant rejections.

The Research and Licence Agreement entered into in December 2006 with Wyeth provided for an initial three-year research term. The new one-year extension will provide Ligand with $3.1m in payments to continue research.

JAK3 is a tyrosine kinase that belongs to the Janus family of enzymes, which appears to have an expression limited to hematopoietic cells and specific inhibitors of JAK3, which could represent a new class of immunosuppressant drugs.

Ligand president and chief executive officer John L Higgins said that the company viewed JAK3 inhibitors as a promising market opportunity.

“We are pleased with the team’s progress and look forward to continued success as we drive the programme forward for Pfizer,” Higgins said.

Ligand is entitled to receive up to $175m in milestone payments for the successful development and commercialisation of multiple products and for royalties on product sales.