Alnylam Pharmaceuticals Inc.’s ALNY, +3.32% rare disease drug Onpattro has been approved by the Food and Drug Administration, marking the first approval of a therapy that employs the RNA interference (RNAi) gene-silencing technique. Onpattro, also called patisiran, is also the first FDA-approved drug for the rare and progressive disease hereditary ATTR amyloidosis with polyneuropathy, or malfunction of bodily nerves. It was shown in clinical trials to improve polyneuropathy and other symptoms. The drug will have an average annual list price of $450,000, though the average effective net price will be around $345,000 when factoring in various discounts, the company said, citing the small patient population affected — or fewer than 3,000 patients currently diagnosed in the U.S. — among other factors. Alnylam also said it has agreed to agreements with major health insurers in which payment depends on how well Onpattro performs; it expects to make the therapy available to ship to health care providers within two days. Friday’s approval marks a milestone for Alnylam as well as the RNAi field, which began about 20 years ago but has been marked by a number of prominent failures. Alnylam was one of few companies that persisted in RNAi development in spite of the field’s difficulties, and has described the therapy as a 15-year journey. Company shares surged nearly 52% after positive late-stage trial results for Onpattro; the stock lifted 3.3% in Friday trade before the halt. Shares have declined nearly 1% over the last three months, compared with a nearly 4% rise in the S&P 500 SPX, -0.71% and a 2% rise in the Dow Jones Industrial Average DJIA, -0.77%
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