Sage Therapeutics says rare disease drug found to be safe in mid-stage study

(Reuters) -Sage Therapeutics said on Tuesday a part of a mid-stage study showed its experimental drug was safe and had some effect in patients with a rare, genetic neurological condition called Huntington's disease.

The company, however, said the study in Huntington's disease patients was not designed to show a statistically significant difference between the drug dalzanemdor and placebo.

The development comes on the back of a mid-stage trial failure for the same drug in April, when it was tested in patients with Parkinson's disease. Shares of Sage Therapeutics have fallen over 13% since then.

The stock, which soared 80% initially premarket, erased those gains and were down more than 3% in early trading.

There was a small numerical difference observed between dalzanemdor and placebo at day 28, on a set of tests which measures cognitive impact of the disease, the company said.

While it was good to note a directional positive change between treatment and placebo, "it is difficult to decipher how much one can read into the 28-day data," said Needham & Co analyst Ami Fadia.

The difference was measured by the HD-Cognitive Assessment Battery or HD-CAB, a composite of six individual tests to assess various domains of cognition relevant to disease.

William Blair analyst Tim Lugo said the study was "underwhelming" and it seemed that the assessment scale was more validated than the drug as it does not provide much data on the activity of dalzanemdor.

The small mid-stage study enrolled 40 patients with the disease and 29 healthy patients.

The two analysts said they were looking forward to data from a larger study, which will assess cognitive impairment over 12 weeks in 178 patients, and better ascertain the treatment's effect.

(Reporting by Sriparna Roy in Bengaluru; Editing by Shailesh Kuber)