Gilead Sciences will buy YM BioSciences for about $510 million, the companies said today, in a deal that expands Gilead’s cancer and inflammation drug pipelines.

The deal is expected to close during the first quarter of 2013. During the second half of the coming year, Gilead said, it plans to launch a pivotal Phase III trial in myelofibrosis of YM’s lead drug candidate CYT387, an oral, once-daily, selective inhibitor of Janus kinase enzymes JAK1 and JAK2.

“Based on promising Phase II data, we believe CYT387 could provide important clinical benefit for patients with myelofibrosis, including potential improvements with regard to anemia and decreased dependence on blood transfusions,” Norbert W. Bischofberger, Ph.D., Gilead’s executive vp, research and development, and CSO, said in a statement. “We look forward to advancing CYT387 into a Phase III study as quickly as possible and to exploring its potential in other myeloproliferative diseases with significant unmet medical need.” 

At the 54th American Society of Hematology Annual Meeting and Exposition in Atlanta on Dec. 9, YM reported positive interim results from a Phase I/II clinical trial of CYT387 in 166 patients with the disease.

“Treatment with CYT387 resulted in rapid and sustained reductions in splenomegaly with a maximal response duration approaching two years. The majority of subjects reporting constitutional symptoms at baseline experienced complete resolution or marked improvement by six months with measurable improvement within the first month of therapy,” according to an abstract of the study archived at the conference website here.

YM acquired the drug in February 10 when it completed a merger with Australian-owned Cytopia, whose founder Andrew Wilks, Ph.D.—now chairman and CEO of SYN|thesis—discovered JAK1 and JAK2.

CYT387 joins a Gilead pipeline that includes idelalisib (formerly GS-1101), a first-in-class specific inhibitor of the phosphoinositide-3 kinase delta isoform that is the company’s lead oncology compound. Gilead is pursuing five Phase III studies of idelalisib in chronic lymphocytic leukemia and indolent non-Hodgkin’s lymphoma. Gilead is also conducting Phase II clinical trials of simtuzumab (formerly GS-6624), an investigational monoclonal antibody drug candidate targeting the human lysyl oxidase-like 2 (LOXL2) protein in myelofibrosis, colorectal cancer, pancreatic cancer, and certain fibrotic diseases.

Once the deal closes, the companies said, YM shareholders will receive $2.95 per common share cash, while holders of warrants and stock options will receive cash equal to the difference between $2.95 and the exercise price of such warrants or options.

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