Shareholders Sue Mereo BioPharma (MREO) Over Brittle Bone Drug Claims

A class action was filed against Mereo BioPharma Group MREO +0.18% ▲ on February 4, 2026.

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Plaintiffs – Mereo shareholders – in the federal securities class action allege that they acquired Mereo American Depositary Shares (“ADS”) at artificially inflated prices between June 5, 2023, and December 26, 2025, known as the “Class Period.” They are now seeking compensation for financial losses incurred upon public revelation of the company’s alleged misconduct during that time. To learn whether you may be eligible for a recovery under this securities lawsuit, click here.

What Does Mereo Do?

Mereo is a biopharmaceutical company based in the United Kingdom. It says that its goal is to help patients battling rare illnesses who currently have few to no treatment options. Mereo says it does this by ensuring they “have access to therapies that can transform their lives.” To that end, Mereo acquires rare drug candidates from other pharmaceutical companies.

Although these companies have heavily invested in these products, they ultimately put them on the backburner “for strategic reasons,” according to Mereo.

So far, the company explains, these  acquisitions have included “three quality clinical stage product candidates from Novartis NVS +1.41% ▲ in 2015 and one from AstraZeneca AZN +0.26% ▲ in 2017.” In late 2020 Mereo entered an agreement for its clinical development program and treatment setrusumab, addressing osteogenesis imperfecta – also known as brittle bone disease, with Ultragenyx RARE +2.01% ▲ .

According to Mereo, Ultragenyx is “a strategic partner with expertise in rare bone diseases.”  Mereo says it retains commercial rights to setrusumab  in Europe, while Ultragenyx holds the rights in the U.S. and elsewhere.

Why are Mereo Shareholders Suing the Company?

• Mereo and two of its senior officers (the “Individual Defendants”) are accused of deceiving investors by lying and withholding important information about its business and prospects during the Class Period.

• In particular, they are accused of omitting truthful information about setrusumab’s ability to achieve statistical significance for the primary endpoints in both the ORBIT and COSMIC studies from SEC filings and related material. By knowingly or recklessly doing so, they allegedly caused Mereo’s ADS to trade at artificially inflated prices during the time in question.

• After a series of partial disclosures, the full truth, according to shareholders, came out on December 29, 2025. That’s when Mereo issued a press release announcing Phase 3 ORBIT and COSMIC results for setrusumab in Osteogenesis imperfecta (OI). The company revealed that neither study achieved statistical significance against the primary endpoints of reduction in annualized clinical fracture rate compared to placebo or bisphosphonates, respectively.

Taking a Closer Look

As alleged, the company and/or Individual Defendants repeatedly made false and misleading public statements throughout the Class Period.

In a press release issued at the beginning of the Class Period, for example, Mereo stated in pertinent part: “[D]ata from the dose-selection Phase 2 portion of the Phase 2/3 Orbit study showing that setrusumab rapidly induced bone production in OI-affected patients. Across all patients evaluated, as of the data cut off, setrusumab demonstrated statistically significant increases in levels of serum P1NP, a sensitive marker of bone formation, and a substantial and significant improvement in bone mineral density (BMD) by 3 months.”

Next, in a January 8, 2024 press release, Mereo’s CEO (an Individual Defendant) stated in relevant part: “2023 was a year of tremendous progress for Mereo. Key milestones in the development of setrusumab for the treatment of OI included positive data from the Phase 2 portion of the Orbit study, and initiation of the Phase 3 portion of the Orbit study and Phase 3 Cosmic study by our partner, Ultragenyx.”

Lastly, in an August 13, 2024 press release, the Company’s CEO stated: “We continued to make significant progress this quarter highlighted by additional positive data from the Phase 2 portion of the ongoing Phase 2/3 Orbit study in patients with OI. These data showed that the statistically significant annualized fracture rate reduction of 67% was maintained following treatment with setrusumab for at least 14 months of follow-up, further demonstrating the potential of setrusumab to generate long-term, clinically meaningful benefit for people living with OI.”

Actions You May Take

If you have purchased the company’s ADS during the Class Period, you may join the class action as a lead plaintiff, remain a passive class member, or opt out of this litigation and pursue individual claims that may not be available to the class as a whole. To learn more about your options, click here.

The deadline to file for lead plaintiff in this class action is April 6, 2026.

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