Regulus Therapeutics' microRNA technology may be risky given its relative newness, but that hasn't kept stodgy pharmaceutical companies from stepping up to the plate. In less than three years since the company was formed by Isis Pharmaceuticals (Nasdaq: ISIS) and Alnylam Pharmaceuticals (Nasdaq: ALNY), it's already done three major licensing partnerships with two pharmaceutical companies.

After a pair of deals with GlaxoSmithKline (NYSE: GSK), it was sanofi-aventis (NYSE: SNY) grabbing a piece of the novel technology yesterday. sanofi will support Regulus' research on up to four different microRNAs targeting fibrosis for three years, with an option to extend the research for two additional years.

Any drugs coming out of the partnership will be taken through the clinic by sanofi with Regulus getting milestone payments and royalties on any drugs that make it to market. All told the deal could be worth $750 million, although it'll start with just a $25 million upfront fee and a $10 million equity investment.

Regulus' parent companies get 7.5% of the initial payment and the future milestone payments. Not a lot of cash, but every bit helps when you don't have significant revenue coming in.

Whether you're better off buying Alnylam or Isis to get a piece of Regulus depends on your risk tolerance. Alnylam is the smaller company, so Regulus makes up a larger percentage of its value. Isis' pipeline is more developed, offering slightly lower risk. Isis' lead drug, mipomersen, partnered with Genzyme (Nasdaq: GENZ), has already shown strong efficacy results in phase 3 trials.

If you do decide to invest, just keep in mind that microRNA therapies are years away from being approved for sale, and plenty of interesting technologies have fizzled out without producing many -- or even any -- useful drugs. Glaxo and sanofi can afford to take a risk on the technology because microRNA therapies are part of their diversified portfolios of drug candidates. Foolish investors looking to invest in microRNAs should do the same.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool owns shares of GlaxoSmithKline and has a disclosure policy.