Alnylam Pharmaceuticals Inc. ALNY shares fell more than 8% premarket on Thursday after advisers to the U.S. Food and Drug Administration on Wednesday weighed the risks and benefits of the company’s treatment for a serious heart condition known as ATTR-CM. The FDA advisory committee voted 9 to 3 that the benefits of the treatment, Onpattro, outweigh its risks in patients with ATTR-CM, but the committee’s comments suggest that the drug’s label may be limited, analysts say. BMO Capital Markets analyst Kostas Biliouris wrote in a note Wednesday that Onpattro’s label will likely be limited to patients who can’t get or tolerate tafamidis, the ATTR-CM treatment sold by Pfizer Inc. PFE as Vyndaqel and Vyndamax. The FDA advisers seemed to agree with the agency’s position that Onpattro’s treatment effect is small, Oppenheimer analysts wrote in a note Thursday, adding, “even in the best-case scenario of an unconditional ATTR-CM indication for Onpattro, we would expect payors to generally restrict access to those who do not adequately respond to tafamidis.” Both analysts maintain outperform ratings on Alnylam shares, saying investors are more focused on the prospects for a different Alnylam product, Amvuttra. Alnylam shares are down 10.9% in the year to date, while the S&P 500 SPX has gained 16.4%.

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