Sirna drug helps vision in blindness-risk patients

Sirna Therapeutics Inc. on Tuesday said its experimental drug to treat the leading cause of Blindness improved vision in almost half of patients in a small, early-stage trial, without causing any drug-related side effects.

The phase I trial results for the company’s lead experimental drug, Sirna-027, are the first human clinical data ever presented for a medicine that employs a technology called RNA interference. Such drugs are designed to prevent disease-causing genes from making their designated proteins.

Dr. Roberto Guerciolini, chief medical officer of the tiny San Francisco-based biotechnology company, said the phase I data involved 14 patients with the Blindness-causing “wet” form of age-related macular degeneration.

All patients received a single intra-eye injection of the medicine and were followed for one to three months. None of them saw a decline in their vision during the study period or evidence of drug-related side effects, Guerciolini said in an interview.

“It was very impressive that more than 45 percent of the patients showed improvement in their visual acuity,” he said, although the trial was too small to show statistical significance.

He said patients deemed to have had improvements in visual acuity were able to see an additional three lines of an eye-test chart following treatment - a standard criterion for patients with the eye problem.

The data were presented at the annual meeting of the Association for Research in Vision and Ophthalmology being held in Fort Lauderdale, Florida.

Guerciolini said three doses of Sirna-027 were tested in the study - 100 micrograms, 200 micrograms and 400 micrograms - and that patients given injections of the highest doses showed the best results.

“Because we did not see a single adverse event in the trial, we are confident enough in our drug’s safety to use higher doses and repeated doses of it in future trials,” Guerciolini said. “And we are hoping they will prove able to benefit a majority of patients.”

Based on the favorable safety and effectiveness data, Guerciolini said the company plans to begin a larger phase II trial using stronger doses of the medicine as soon as November, about three months sooner than Sirna’s earlier plans.

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