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What: Shareholders of Rigel Pharmaceuticals (NASDAQ:RIGL), a small-cap clinical stage biopharma, are having a pleasant Tuesday. The company's stock is soaring, up more than 36% as of 11:15 a.m. EDT after management released encouraging data from Rigel's first FIT phase 3 clinical trial.

So what: The trial was designed to measure Fostamatinib's, the company's lead compound, ability to raise blood platelet levels in adult patients with primary chronic immune thrombocytopenia, or ITP. This disease causes a patient's own immune system to seek out and destroy blood platelets, which are critical for healing and clotting.

The study showed that 18% of patients who used Fostamatinib were able to achieve a stable platelet response, which was defined as 50,000 platelets per uL of blood on at least four of the last six scheduled clinic visits. That result compared favorably to the 0% response rate observed in the control group and was shown to be statistically significant. In addition, the safety profile of the compound was consistent with prior clinical experience.

The patients who met the study's primary endpoint platelet counts, an increase from a median starting point of 16,000/uL to a median over 100,000/uL at week 24, have all since enrolled in the long-term phase 3 extension study and have maintained elevated platelet levels beyond the initial 24 week study period.

Given the good clinical news all around it's easy to understand why shares are popping.

Now what: Results from Rigel's second FIT phase 3 study are expected to be released in October or November of this year. If these same results are reproduced in that study as well as during an interim look at the on-going phase 3 extension study, then Rigel plans on submitting Fostamatinib for regulatory review in the first quarter of 2017.

There are approximately 50,000 to 60,000 adult patients in the U.S. who are living with primary chronic ITP. That's a relatively small patient population, so the FDA has already decided to give Fostamatinib Orphan drug status. That should allow Rigel to charge a huge premium if the drug can find its way to market, which is why some analysts foresee peak sales running above $350 million. That's a lot of money when compared to Rigel's current market cap of only $340 million.

While I understand the market's optimism given the clinical result, Rigel still has plenty of work ahead of it before Fostamatinib can start to actually produce revenue. For that reason potential investors might want to wait until the second round of FIT data is available later this year before they consider jumping in.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.