* FDA panel will consider product at Tuesday meeting
* Product already has FDA approval for limited use
* Stryker shares fall 1.7 percent (Adds analyst comment, updates shares)
By Lisa Richwine
WASHINGTON, March 27 (Reuters) - U.S. reviewers raised doubts about safety and effectiveness data supplied by Stryker Corp (SYK.N) on a bone-growth putty for spinal surgery.
“Based on reviews of these data, the agency has questions whether or not this combination product can be considered relatively safe and effective when compared to” a control treatment, Food and Drug Administration staff said in an analysis released on Friday.
The agency will ask an advisory panel at a public meeting on Tuesday if Stryker has provided adequate information to support wider approval of the product, OP-1 Putty.
The product already has FDA approval for limited use in certain spine surgeries to treat back pain.
Stryker, in a separate summary prepared for the advisory panel, said its data showed OP-1 Putty “has equivalent clinical and radiographic outcomes” to a bone-fusion procedure, without the complications.
Stryker shares fell 1.7 percent to close at $34.35 on the New York Stock Exchange.
The advisory panel’s discussion may be more favorable than expected but it is unlikely Stryker will win approval with the current data, JP Morgan analyst Michael Weinstein said.
“We do believe that the product has demonstrated a clinical effect” and the outside experts on the panel “are likely to acknowledge the bright spots in the data,” Weinstein said in a research note.
The OP-1 Putty contains a genetically engineered protein designed to stimulate bone growth. Surgeons implant the putty between vertebrae to fuse the bones and relieve lower back pain.
A Stryker study compared the putty to a procedure in which surgeons take a piece of bone from a patient’s hip and use it to fuse the vertebrae.
FDA reviewers said three different analyses of the study showed the putty failed to perform as well as the comparison treatment.
Stryker presented a fourth analysis that the company said showed comparable success between both treatments.
FDA reviewers, however, said they had concerns about how the company reached that conclusion, including the use of different follow-up periods for evaluating if the treatment worked.
The agency staff also raised safety concerns about possible long-term effects from antibodies developed in response to the bone-growth protein.
“The agency believes that there are safety questions associated with the immune response to the product,” the staff summary said.
The FDA usually follows recommendations from its advisory panels of outside experts but is not required to.
The agency also has concerns about the manufacturing of the OP-1 Putty, but those are not subject to panel discussion, the staff summary said. (Reporting by Lisa Richwine; editing by John Wallace, Dave Zimmerman)