BioWorld International Correspondent

LONDON - Celltech Group plc and Amgen Inc. entered a collaboration to develop antibody treatments for osteoporosis, focusing on sclerostin, a protein target involved in the regulation of bone deposition that was discovered at Celltech's genomics facility in Seattle.

No financial details were disclosed, but the deal gives Amgen, of Thousand Oaks, Calif., exclusive worldwide rights to develop and market treatments that target sclerostin. The lead compound in the collaboration is a high-affinity pegylated antibody fragment that Celltech is in the process of generating. It is expected to enter preclinical development next year.

Apart from bearing the costs of producing the antibody, Celltech, based in Slough, will pay Amgen a proportion of all development costs up to the end of Phase II. Depending on the Phase II results, Celltech would then either continue to co-invest in Phase III and have European marketing rights, or hand the full rights to Amgen and take milestones and royalties.

Richard Bungay, Celltech's director of corporate communications, told BioWorld International, "There are clinical development milestones but we haven't disclosed them because Celltech is at the point where it is profitable and doesn't need to quote headline figures."

Despite having funds, Celltech needed to partner the program at an early stage because it did not have the skills to take sclerostin forward. "This is one of the few programs we said we would actively look to partner early," he said. "We have a lack of clinical expertise in bone biology, a very specialized area. Conversely, Amgen has built up expertise in the area over the past three to four years, making them an excellent partner."

The partners said sclerostin could be an important target because it is involved in increasing bone density and thus would be different than current treatments, which prevent further bone loss.

Celltech's genomics unit in Seattle worked with academic researchers Peter Beighton and Herman Hamersma at the University of Cape Town in South Africa to study members of the Afrikaner population suffering from a rare condition known as sclerosteosis, in which bones continue to gain mass throughout life. The condition is known to occur with frequency only among Afrikaners, a population of Dutch descent that settled in South Africa in the late 17th century.

By comparing the DNA of affected families with nonaffected families, the mutation was mapped to a single chromosome. The defect leads to premature termination of sclerostin, triggering bone deposition, and is thus a genetic surrogate for what a drug for osteoporosis would be required to do.

Bungay said it is the view of both companies that "antibodies will be far and away the best approach to inhibit sclerostin." However, the development of small-molecule inhibitors is covered by the deal, as is the extension of the program into other indications.

Bungay added, "We believe this is a significant deal overall, though it is hard for the market as of today to say it is valuable because any products are some way out."