Alnylam tumbles after warning of potential demand hit from drug pricing changes

** Shares of drugmaker Alnylam Pharmaceuticals ALNY.O fall 14.9% to $197.8, touching their lowest level since June 2024

** ALNY trading was briefly paused for volatility

** Certain Medicare Advantage plans require patients to try other therapies before Amvuttra, and more payors could follow, that could "adversely affect demand" and revenue for the drug, co says in filing

** Amvuttra is Alnylam's major growth driver and treats a heart condition known as transthyretin amyloid cardiomyopathy (ATTR-CM)

** Co says changes to the 340B drug pricing, that requires pharma cos to offer medicines at lower prices to certain hospitals and clinics, "may adversely affect the demand" for their products

** Stifel downgrades stock to "hold" from "buy" and cuts PT to $225 from $318 citing slowing Amvuttra growth, expectations for lower near-term sales estimates

** "Potential 340B changes remain an overhang for the stock," Stifel adds

** 24 of 32 brokerages rate the stock "buy" or higher, and 8 "hold"; their median PT is $349.5

** Including session's moves, stock is doubt about 50% YTD