"Rivals may profit off Celgene’s pain. Novartis AG (ADR)'s Gilenya and Arena Pharmaceuticals, Inc.’s etrasimod were expected to cede market share to ozanimod — a threat that weighed on the developers’ theses."
Novartis could take control of this market with an acquisition of Arena (through selling stake in Roche) if they believe Etrasimod would otherwise threaten Gilenya.