Doctors are being contacted to organize a clinical trial for a copy of Teva Pharmaceutical’s multiple sclerosis medicine Copaxone, according to a report in FiercePharma.

The prospect of clinical studies could mean a generic version of Teva’s biggest-selling product is delayed by two years, said Natali Gotlieb, a Tel Aviv-based analyst for Israel Brokerage & Investments. The Israeli drugmaker has sued to block copies from Swiss drugmaker Novartis and partner Momenta Pharmaceuticals and from U.S. generic-drug maker Mylan.

Jon Congleton, general manager of Teva’s U.S. neuroscience unit, told investors during a teleconference yesterday that Teva has heard talk about doctors being contacted about the trial but hasn’t seen actual patient recruitment begin. The conference was organized by investment bank Cowen & Company, according to a transcript. Teva does not know which drugmaker may be organizing the trial, he said.

Copaxone had sales of $3.3 billion last year. Teva has said the 14-year-old injected treatment is too complicated to copy without patient trials to prove a generic version is as effective as the original.

“It would be great news for Teva, the best news,” if a clinical trial were required, said Gotlieb. “It will take them longer to achieve approval and would be expensive to run clinical trials.”

A trial could delay U.S. approval of a Copaxone generic for two years, including six months to one year to conduct the trial and a year to review the results and submit data to the FDA, Gotlieb said.

Momenta spokeswoman Beverly Holley said Momenta is seeking approval for its copy as a generic in an FDA application process that doesn’t require clinical trials.