Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Arrowhead Research (NASDAQ:ARWR), a clinical-stage biopharmaceutical company focused on developing RNAi-based therapeutics, tumbled as much as 11% after the company announced a new clinical candidate.

So what: According to the company's midday press release, Arrowhead's next clinical candidate will be ARC-AAT, an RNAi therapeutic targeted at liver disease associated with Alpha-1 antitrypsin deficiency, or AATD. In the words of Arrowhead's president and CEO Christopher Anzalone, "ARC-AAT is designed to inhibit the production of mutant AAT protein in the liver and in preclinical studies it has shown high levels of knockdown with long duration of action." In primate studies, Arrowhead noted an AAT reduction of greater than 80% at the six-week mark. Initial studies will examine adult patients with signs of liver injury, but further clinical investigations may be undertaken for children.

Now what: Today's move lower looks more like profit taking tied to the fact that shares surged around 35% during the prior four days, rather than a genuine reaction to the release of a new clinical candidate. Obviously, there are plenty of questions that will surround ARC-AAT, and Arrowhead investors can now expect research and development costs to increase as a new clinical study is added to the pipeline. However, Cincinnati Children's hospital is estimating that as many as one in 3,000 people may have AATD, and many people currently undiagnosed; therefore, if ARC-AAT is successful in human studies, it could prove to have quite the bounty of opportunity.

Sean Williams has no material interest in any companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

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