Wells Fargo analyst Jim Birchenough upgraded Arena Pharmaceuticals (ARNA) to Outperform and raised his price target for the shares to $53 from $19. The stock closed yesterday up 7% to $36.21.

An improved FDA environment could facilitate approval of ralinepag in pulmonary arterial hypertension, Birchenough tells investors in a research note. He's upgrading the shares ahead of the Phase 2 data for S1P modulator etrasimod in ulcerative colitis.

The analyst believes recent data from Celgene's (CELG) competing S1P modulator ozanimod "lowers the bar for differentiation." Both of Arena's assets "could attract large Pharma interest," Birchenough adds.