Dear Valued Visitor,

We have noticed that you are using an ad blocker software.

Although advertisements on the web pages may degrade your experience, our business certainly depends on them and we can only keep providing you high-quality research based articles as long as we can display ads on our pages.

To view this article, you can disable your ad blocker and refresh this page or simply login.

We only allow registered users to use ad blockers. You can sign up for free by clicking here or you can login if you are already a member.

AstraZeneca plc (ADR) (AZN), Rigel Pharmaceuticals, Inc. (RIGL): Growing Aches and Pains Sink This Stock

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 Rigel Pharmaceuticals, Inc. (NASDAQ:RIGL) imploded today, losing as much as 37% of its value after licensing partner AstraZeneca plc (ADR) (NYSE:AZN) announced that the first phase 3 study of Fostamatinib failed to meet one of the two designed primary endpoints of the trial.

AstraZeneca plc

So what: Fostamatinib — a treatment for rheumatoid arthritis, or RA, which is a progressive disease that causes inflammation of the joints and surrounding tissues – achieved a statistically significant improvement in the ACR20 response rate in terms of symptoms for both dosage subsets at 24 weeks. However, it didn’t show any improvement with regard to progression of joint damage according to x-ray tests. Further, Fostamatinib was generally well-tolerated in trials, but it once again did lead to hypertension, which is a concern not taken lightly by the Food and Drug Administration.

Now what: That’s now two strikes for Rigel Pharmaceuticals, Inc. (NASDAQ:RIGL) with Fostamatinib — one more and it and the drug can take a seat on the bench as far as I’m concerned. In December, Fostamatinib proved to be an inferior treatment option for patients with RA in a direct comparison to AbbVie Inc (NYSE:ABBV)‘s blockbuster drug Humira — strike one. Today, it failed to demonstrate any statistically significant improvement in suppressing joint damage — strike two. Tack on the fact that Pfizer Inc. (NYSE:PFE)‘s Xeljanz, another FDA-approved treatment for RA, scored higher than Fostamatinib in its ACR20 response rate in its phase 3 tests and doesn’t have hypertension concerns, and you can see that even if Fostamatinib somehow gains approval, its uses appear to be extremely limited. Rigel Pharmaceuticals, Inc. (NASDAQ:RIGL) still has two additional late-stage trials ongoing with Fostamatinib, but the expectation that they will be a success are quickly waning.

Craving more input? Start by adding Rigel Pharmaceuticals to your free and personalized watchlist so you can keep up on the latest news with the company.

The article Growing Aches and Pains Sink Rigel Pharmaceuticals originally appeared on and is written by Sean Williams.

Fool contributor 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.

Copyright © 1995 – 2013 The Motley Fool, LLC. All rights reserved. The Motley Fool has a disclosure policy.