It looks like the reality of the risk of failure for RNAi drugs has finally set in for big pharma.

After landing substantial deals with Biogen Idec (NASDAQ:BIIB), Medtronic (NYSE:MDT), Novartis (NYSE:NVS), and Merck (NYSE:MRK), who did Alnylam (NASDAQ:ALNY) finally get to partner its lead compound, respiratory syncytial virus (RSV) infection treatment ALN-RSV01? ... Cubist Pharmaceuticals (NASDAQ:CBST).

Cubist? Really? I mean, I don't have anything against the company. Heck, it's one of my top scorers in Motley Fool CAPS, but we're not exactly talking a powerhouse here. The company's market cap isn't that much larger than Alnylam's. Not, like, Merck-sized bigger.

And the deal doesn't look like it's benefiting Alnylam that much either. Alnylam is getting only $20 million up front and $82.5 million in potential milestone payments in exchange for giving up 50% of its U.S. stake. Cubist gets full rights to the drug outside of North America and Asia, with Alnylam entitled to double-digit royalties on those net sales. That seems awfully low given that the potential for ALN-RSV01 is huge, especially if it can fight RSV and not just prevent it. AstraZeneca's (NYSE:AZN) prophylactic RSV treatment, Synagis, is on pace to be a blockbuster with sales of $724 million in the first nine months of last year.

My problem with RNAi has never been its potential. Instead, it's that the technology, which lowers the stability of RNA and can effectively shut down protein production of a specific gene, hasn't really been proven to work in humans yet. Those monster deals that pharmaceutical companies signed in recent years just seemed too risky to me for a technology that might not work or might take years to refine. Gene therapy anyone?

I may be reading more into Alnylam's deal than I should, but it looks to me like big pharma has finally come to its senses and passed on RNAi, at least with this one.

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Fool contributor Brian Orelli, Ph.D., has been breaking in and out of the top 1% of CAPS for months now; he's currently out with a rating of 98.97. He doesn't own shares of any company mentioned in this article. Biogen Idec is a Stock Advisor pick. The Fool has a disclosure policy.