ALNY Chart

What: According to data provided by S&P Global Market Intelligence, shares of the rare disease drugmaker Alnylam Pharmaceuticals (NASDAQ:ALNY) lost over a quarter of their value last month. The good news is that Alnylam's hefty monthly slide was apparently driven by the broader sell-off across the entire biotech landscape -- not a negative clinical or regulatory update.

So what: Alnylam's shares have been garnering a substantial premium based mainly on the prospects of its late-stage drug patisiran, indicated as a potential treatment for the fatal neurodegenerative disease Familial Amyloidotic Polyneuropathy, or FAP. Using Pfizer's EU-approved medicine Vyndaqel as a starting point, analysts think that patisiran could generate around $800 million in peak sales.

The problem is that patisiran probably won't see a regulatory filing until at least 2017, putting its commercial launch on track for perhaps 2018. Complicating matters further, Ionis Pharmaceuticals also has a late-stage candidate, IONIS-TTRRx, in development for FAP that's neck and neck with patisiran in terms of its clinical progress. 

Now what: Per the company's update at last month's J.P. Morgan Healthcare conference, the drugmaker should release over 10 clinical updates for its broad pipeline this year. Unfortunately, there won't be a single late-stage data readout among them. So, given the market's overtly negative view of risky developmental-stage biotechs of late and the company's lack of major clinical catalysts in the near-term, Alnylam may struggle to reverse this downward trend until a sea-shift in sentiment takes place. That's why investors may want to hold off on picking up shares in this promising RNAi drug specialist for the time being. 

George Budwell owns shares of Pfizer. The Motley Fool owns shares of and recommends Alnylam Pharmaceuticals and Ionis Pharmaceuticals. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.