After bashing RNAi over the past few years -- see here and here for examples -- I think the pioneering technology is looking a little more appetizing.

The field has advanced, but more importantly, the prices have come down. A lot.

In 2006, Merck (NYSE: MRK) bought Sirna Therapeutics for $1.1 billion. In 2008, Alnylam Pharmaceuticals (Nasdaq: ALNY) was a $1.4 billion company. Given the unproven nature of the technology, that was just ridiculous.

Now Alnylam has a market cap around $400 million and has a war chest of more than $230 million in cash and short-term investments, giving it time to develop RNAi drugs. That looks much more reasonable than yesteryear.

RNAi has nothing to do with Apple
If it did, there'd probably be multiple products on the market already. Unfortunately, drugs are a lot harder to develop than electronics.

Instead, the "i" here stands for interference. RNA is the molecule that translates the genes on your DNA into proteins that do the work in the cell. By interfering with the RNA, you can decrease or eliminate a protein. You can think of RNAi as acting one step up from antibodies such as Pfizer (NYSE: PFE) and Amgen's (Nasdaq: AMGN) Enbrel or Bristol-Myers Squibb (NYSE: BMY) and Eli Lilly's (NYSE: LLY) Erbitux, which act directly on the protein after it's already formed.

At this point, Alnylam is the best pure play on RNAi. Its ALN-RSV01 is in phase 2 development to treat respiratory syncytial virus infection, a lung infection that affects infants and the elderly. Attacking a virus in a localized infection was a good initial choice for Alnylam.

Alnylam has also licensed its technology to multiple drugmakers. The technology probably won't work for every target, but if it works for RSV, investors should be confident that Alnylam might be able to bring in royalties from the licenses it has made over the years.

Not everyone loves RNAi
Roche announced earlier this month that it was stepping out of the RNAi-development business. The decision was rather surprising since Roche had spent money buying a facility and licensing technology from Alnylam and had licensed a separate nanoparticle technology for delivering RNAi molecules to cells from Tekmira.

If Roche thought there was a future in RNAi drug development, wouldn't it have continued research? Possibly, but there are a lot of reasons why a drug developer might discontinue development.

As an example, compare a me-too drug going after a proven drug target and a drug going after a novel drug target. The former is low risk compared to the latter, but the me-too drug also has a fairly low reward since it'll have to compete with the drug it's following.

RNAi is most definitely a high-risk, high-reward technology. It's possible that Roche just didn't have a spot in its revamped pipeline for that kind of drug development.

Novartis (NYSE: NVS) also ditched Alnylam earlier this year, but that one is easier to explain. The duo developed 31 potential drug targets together, which was likely more than enough for Novartis to handle.

At these prices, Alnylam is looking a lot more appetizing than it was a few years ago. The risk-reward profile looks more like it's in investors' favor. I'm not ready to buy in quite yet; a spot on the watchlist is more appropriate at this point.

That isn't to say you shouldn't buy right now. Just like Roche and Alnylam have separate risk-reward profiles, you might have a different profile than I do. Even if RNAi drugs haven't bottomed out, the margin of safety has increased considerably after the recent price drops.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Pfizer is a Motley Fool Inside Value pick. Novartis is a Motley Fool Global Gains choice. 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 Fool has a disclosure policy.