Mereo BioPharma Class Action Filed Over Failed Phase 3 Trials After 87% Share Collapse
Mereo BioPharma faces a class action over ADS purchases June 5, 2023–December 26, 2025 for allegedly misrepresenting setrusumab’s ORBIT and COSMIC Phase 3 prospects. December 29, 2025 disclosures showed both trials failed AFR endpoints, triggering an 87% collapse from $2.31 to $0.29 and setting an April 6, 2026 lead-plaintiff deadline.
1. Lawsuit Filing
On February 14, 2026, a class action was filed on behalf of all investors who acquired Mereo BioPharma ADS between June 5, 2023 and December 26, 2025. Plaintiffs allege executives made false and misleading statements about the likelihood of success for the company’s setrusumab Phase 3 trials, seeking damages for the alleged inflation of share value.
2. Phase 3 Trial Failures
The complaint centers on the ORBIT and COSMIC studies, both designed to demonstrate a statistically significant reduction in annualized fracture rate (AFR). On December 29, 2025, Mereo disclosed neither trial met its primary endpoint and improvements in bone mineral density failed to offset core efficacy failures.
3. Share Price Collapse
Following the December disclosure, Mereo’s ADS shares plunged from $2.31 to $0.29 in a single trading session, an 87% loss of shareholder value. Investors must file motions by April 6, 2026 to seek appointment as lead plaintiff in the litigation.