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What: Alnylam Pharmaceuticals (ALNY -0.31%) closed up 10.7% on Friday after presenting data from its ongoing phase 2 open-label extension trials for patisiran and revusiran at the XV International Symposium on Amyloidosis.

So what: After two years of treatment with patisiran, patients with familial amyloidotic polyneuropathy (FAP) had a mean 6.7 point decrease in their Modified Neuropathy Impairment Score (mNIS+7), a measurement of motor strength, reflexes, sensation, and other factors. Alnylam Pharmaceuticals estimates that untreated FAP patients would have seen their mNIS+7 score increase by 26 to 30 points over two years.

The phase 2 trial for revusiran, which treats familial amyloidotic cardiomyopathy (FAC), the version of the disease that primarily affects the heart rather than the nervous system, was started later than the FAP trial, so it only has data out to one year.

The FAC patients were given a 6-minute walk test, which Eric Green, Alnylam's VP and general manager of its TTR Program, characterized as "generally stable" in a "majority of evaluable" patients. In other words, revusiran might be helping some patients but not others, which the company hypothesizes could be due to the time between when the patient was diagnosed and when they started treatment -- more-advanced patients seem to be responding less. Patients in the phase 3 trial are less-advanced than those in the phase 2 trial, so the hope is revusiran will be able to help them.

Now what: The open-label extensions are designed to get long-term safety data; Alnylam Pharmaceuticals still needs positive phase 3 data to get the drugs approved. But the data presented today bode well for the potential for a successful phase 3 trial for patisiran and possibly revusiran.

APOLLO, the phase 3 trial for patisiran, is scheduled to read out in mid-2017 and ENDEAVOUR, the phase 3 study for revusiran, will have data in early 2018.