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 , a clinical-stage biopharmaceutical company focused on autoimmune, inflammatory, and muscle disease disorders, dropped as much as 17% after announcing that R343 didn't meet its primary endpoint in a mid-stage allergic asthma study.

So what: R343 is an inhaled SYK inhibitor that, according to this phase 2 trial, was to hit a predefined change in pre-bronchodilator FEV1 (a measure of lung function that takes into account expelled air volume in the first second) from the start of the trial to the end at week eight relative to the placebo. Although Rigel noted that the drug was safe and well-tolerated, it did not meet either its primary or secondary endpoints, and development of the drug will be ceased.


Now what: Disappointments are becoming all too common for Rigel, which saw its shares implode in June after its then-development-partner AstraZeneca decided to take a $140 million charge and return all rights to rheumatoid arthritis pill fostamatinib, its lead drug candidate, back to Rigel. A good chunk of fostamatinib's top-line data from its late-stage studies have been statistically significant; however, AstraZeneca saw no need to pour additional money into the program. What's left to buoy Rigel now is its $252 million in cash with no debt. But considering that it will likely burn through $80 million to $90 million per year in cash, that's not a big comfort to existing shareholders.

Rigel's recent troubles could serve as the perfect reminder that the best investment strategy is to pick great companies and stick with them for the long term. The Motley Fool's free report "3 Stocks That Will Help You Retire Rich" not only shares stocks that could help you build long-term wealth, but also winning strategies that every investor should know. Click here to grab your free copy today.

The article Why Rigel Pharmaceuticals Shares Tanked originally appeared on Fool.com.

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. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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