Why is Corcept Therapeutics stock tumbling today? By Investing.com

• Corcept Therapeutics shares fell 12.9% after rival Genmab's Phase 3 trial succeeded in the same cancer indication • Genmab's rinatabart sesutecan met primary and secondary endpoints, threatening Corcept's approved drug Lifyorli • Decline compounded by prior analyst downgrade, October weakness, and neutral broader market Corcept Therapeutics (CORT) shares dropped 12.9% intraday after Genmab announced its Phase 3 RAINFOL-02 trial of rinatabart sesutecan (Rina-S) met both its primary progression-free survival endpoint and key secondary overall survival endpoint in platinum-resistant ovarian cancer, with statistically significant, clinically meaningful improvements over chemotherapy. The result directly threatens Corcept's Lifyorli (relacorilant), approved by the FDA earlier in 2026 for the same patient population and a key growth driver for the company. The move added to existing pressure: an analyst downgrade earlier in the month and a roughly 9.5% October decline already preceded the news, with Q3 earnings due late October or early November. Broader markets were mixed, offering no offsetting support, and Genmab's own shares rallied on the news. Corcept shares opened near $106.05, fell to a session low of $90.99, and partially recovered to $93.68.