Piper Jaffray analyst Edward Tenthoff lowered his price target for Alnylam Pharmaceuticals to $110 from $126 after the company said it discontinued dosing of fitusiran in all ongoing studies following a fatal thrombotic event in a Hemophilia A patient.

The stock in premarket trading is down 12%, or $10.52, to $75.50. The analyst believes the death is related to fitusiran mechanism and not more broadly the RNAi platform. As such, he's a buyer of Alnylam shares on today's weakness ahead of the Phase III Apollo data on patisiran in 225 hereditary ATTR Amyloidosis with Polyneuropathy patients in late September.

While Tenthoff expects Alnylam will be able to re-initiate dosing of fitusiran and the Atlas studies with protocol adjustments, he "conservatively" removed all value for fitusiran, which dropped his price target.