Mereo BioPharma Group plc ($MREO) Misled Investors About Setrusumab Phase 3 Trial Prospects Case

S.D. New York

Court

1:26-cv-00988

Case number

06/05/2023

Class period Start

12/26/2025

Class period End

04/06/2026

Lead Plaintiff motion deadline

$MREO investors filed a claim against Mereo BioPharma Group plc for allegedly misleading investors about the likelihood that its Phase 3 ORBIT and COSMIC studies for setrusumab would achieve statistical significance on the primary endpoint of reducing annualized fracture rate in osteogenesis imperfecta (OI).
After the company disclosed that the Phase 3 trials failed to meet statistical significance on the primary endpoint, $MREO fell 87.7% from $2.31 on December 26, 2025 to $0.29 on December 29, 2025.
$MREO investors can join this case to be notified about potential recovery.

Case Details:

Between June 5, 2023 and December 26, 2025, Mereo told investors that setrusumab was showing strong potential and that its late-stage program was progressing toward meaningful results, including confidence that improvements in bone mineral density would translate into reduced fracture rates and successful Phase 3 outcomes.

However, during this period, investors allege the company overstated the clinical implications of earlier data and concealed material risks about whether the Phase 3 ORBIT and COSMIC trials could actually achieve statistical significance on their primary fracture-rate endpoints. Investors further allege Mereo failed to disclose that the trials were unlikely to meet the primary endpoints of reducing annualized clinical fracture rate versus placebo/bisphosphonate controls.

Then, on July 9, 2025, Mereo disclosed that the Phase 3 ORBIT study failed to achieve statistical significance at the second interim analysis, and the stock dropped about 42.52%, from $2.94 (July 9, 2025 close) to $1.69 (July 10, 2025 close).

Additional revelations followed on December 29, 2025, when Mereo announced that neither ORBIT nor COSMIC achieved statistical significance on the primary endpoint (reduction in annualized clinical fracture rate), despite improvements in bone mineral density. By December 29, 2025, shares had dropped to $0.29, representing a total decline of 87.7% from $2.31 on December 26, 2025 over the final correction period.

Based on these events, $MREO investors filed a claim against Mereo BioPharma Group plc, alleging the company:
It misrepresented the likelihood that setrusumab would achieve statistical significance on Phase 3 primary endpoints tied to fracture-rate reduction
It failed to disclose material adverse facts about the true prospects of ORBIT and COSMIC meeting their primary endpoints versus control groups
It misled investors about the clinical and statistical support for projecting fracture-rate reductions, inflating $MREO’s ADS price until the truth emerged
Investors argue Mereo misled the market about the real probability of Phase 3 success for setrusumab in OI, causing losses when the company revealed the trials did not meet the primary endpoint as previously suggested.

Case Type

US Securities Class Action

Case Status

Lead Plaintiff Appointment

Alleged Offence

Misleading Statements,

Financial Misrepresentation,

Failure to Disclose,

Omissions

Suspected Party

Management

Security Type

Depository Securities (ADS, ADR, GDR)

Trade Direction

Long

Shock Event Date

12/29/2025

Filing date

02/04/2026

Lead Plaintiff Deadline

04/06/2026

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