By Matthew Willett

Curis Inc. and OP-1 implant partner Stryker Corp. found the premarket approval application for the bone graft implant deemed unapprovable by the FDA in a letter that cited a lack of statistical equivalence as compared to control treatment of autograft.

Curis' stock fell 47 percent on the news.

The OP-1 implant for treatment of nonunion fractures of the tibia, licensed for orthopedic and periodontal indications by Curis to Stryker, of Kalamazoo, Mich., for royalty payments, was a Creative BioMolecules candidate when that company merged with Ontogeny Inc. and ReproGenesis Inc. to form Curis last year. (See BioWorld Today, Feb. 16, 2000.)

According to Curis, the FDA cited deficiencies related to the lack of statistical equivalence compared to control, and recommended Stryker conduct a new study.

Stryker officials could not be reached for comment.

Curis said Stryker will continue its efforts toward approval for the implant, a bone graft treatment that combines osteogenic protein-1 (OP-1) and a re-absorbable collagen scaffold. When put in place the implant is designed to induce a specialized bone cell reaction that begins normal regeneration.

Stryker Biotech, the Stryker Corp. subsidiary responsible for OP-1's clinical development, said it will continue to pursue regulatory approval for the bone graft product, according to Curis.

Curis' vice president of corporate communications, Bill Boni, said the nonapprovable letter from the FDA concerning OP-1 doesn't change his company's position.

"We do not know yet, and won't know [whether the program will be delayed], until Stryker has its meeting with the FDA," Boni said. "It's not affecting the status of our other programs at all."

Boni added that Stryker is responsible for the program's clinical advancement, and that Curis has little to do with the program beyond that.

"Curis' role in this at this point is to collect royalties when the product is approved, up to a mid-teens rate," Boni said. "It's never pleasant when a near-term product encounters this kind of blockage; however, the good news is that we have other products about to begin clinical testing."

Though Boni couldn't comment on Stryker's clinical advancement plans for OP-1, he said the company is pursuing testing on further indications including spinal fusion and fresh fractures. He also expressed surprise that the FDA would return a nonapprovable recommendation after favorable European regulatory agency decisions.

"It's interesting that this decision by the FDA should follow on the heels of a unanimous recommendation in Europe to recommend OP-1 for approval," he said. "We were surprised following the unanimous positive recommendation in Europe that the FDA issued a nonapprovable letter."

Curis' stock (NASDAQ:CRIS) fell 47 percent, or $6.062, on the news Tuesday to close at $6.937.