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What: Shares of Arena Pharmaceuticals (NASDAQ:ARNA) have been gaining strength Wednesday morning, and currently hold a gain of more than 33% as of this writing. Wednesday's spike followed pre-market news of positive results from Arena's Phase 1b trial of autoimmune treatment APD334.

So what: APD334 is designed to lower blood lymphocyte counts by targeting the sphingosine 1-phosphate subtype receptor, and its early results are evidently promising. A double-blind placebo-controlled trial with 60 total participants (10 received placebos) showed a mean decrease of 69% from baseline lymphocyte counts, with recovery to baseline occurring in about a week after the final dose. According to Arena's Chief Medical Officer William R. Shanahan, this degree of reduction is in line with the efficacy of similar drugs in their Phase 2 and Phase 3 trials.

Now what: Arena now plans to push ahead into Phase 2 trials for APD334 for treatment of ulcerative colitis and Crohn's disease, which make up many of the 1.4 known million cases of inflammatory bowel disease in the United States. Autoimmune disorders are so widespread that AbbVie's Humira  -- which is used to treat Crohn's and ulcerative colitis as well as rheumatoid arthritis and other inflammatory diseases -- was the best-selling drug in the world by revenue for 2013. If Arena can capture even a small slice of that revenue pie with APD334, it could be a potential steal at today's prices, even after its huge pop.

Alex Planes has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not 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.