Arena surges on Phase I data for S1PR1 candidate

Arena Pharmaceuticals Inc. (NASDAQ:ARNA) added $2.53 (76%) to $5.85 on Wednesday, increasing its market cap to $1.3 billion, after reporting top-line results of a Phase Ib study of APD334, a sphingosine 1-phosphate receptor 1 ( S1PR1; S1P1; EDG1) agonist, to treat autoimmune diseases.

Patients receiving a 21-day course of APD334 had a dose-dependent lowering of lymphocyte counts, with a maximum reduction of 69%. Arena said the effect was reversible, with counts returning to baseline within one week. ...