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TORONTO, Jan 30 (Reuters) - BioMS Medical Corp (MS.TO: Quote, Profile, Research) (MS.TO: Quote, Profile, Research) on Friday said its lead drug for the treatment of multiple sclerosis failed to meet a main goal in a mid-stage study , sending the company's shares down more than 50 percent.

The small biotech said the study showed the drug did not prevent symptoms from coming back. People who took the drug were just as likely to have symptoms return after 15 months as patients who did not take it.

"We have long believed that the outcome of this study would be very uncertain, given that this trial was statistically underpowered and that the compound was not previously tested on humans for this indication," Maher Yaghi, an analyst at Desjardins Securities in Montreal, said in a research note.

Yaghi downgraded BioMS stock to "hold" from "buy" earlier this week in anticipation of the test results. However, he maintained his price target of C$5.75 a share.

The shares were down 34.4 percent at C$2.25 by afternoon, after touching a one-year low of C$1.51 earlier in the day.

The drug, which was being tested in patients with relapsing-remitting multiple sclerosis (RRMS) did, however, show signs of slowing down the progression of the crippling disease.

"The results are more positive than negative," said Douglas Loe, an analyst at Versant Partners. "The aspects by which the drug did perform well in this trial are those that which are germane to performance in its pivotal secondary progressive MS trial, which is a separate clinical program."

Loe said that program is seen as key to partner Eli Lilly (LLY.N: Quote, Profile, Research), which signed a licensing and development deal with BioMS in 2007.