Novartis’s pivotal antibody drug Cosentyx failed to outperform placebo in a Phase 3 clinical trial targeting giant cell arteritis (GCA), a rare autoimmune disorder impacting blood vessels. The setback limits Cosentyx’s potential to compete with existing therapies by Roche and AbbVie that are approved for GCA treatment. This outcome underscores the challenges in expanding indications for blockbuster biologics amid highly specific disease mechanisms.