Here's Why Arena Pharmaceuticals Jumped Higher Today

Shares of Arena Pharmaceuticals (NASDAQ: ARNA) are up 13% at 2:13 p.m. EDT because its rival, Bristol Myers Squibb (NYSE: BMY), reported positive data on Zeposia in patients with ulcerative colitis. Zeposia targets the sphingosine-1-phosphate (S1P) receptor, just like Arena's etrasimod. Typically, good data from a rival drugmaker would send shares down, not up, but ulcerative colitis is a common enough disease -- around a million Americans have it -- that there's enough room in the marketplace for more than one drug.