On March 19, 2026 Mereo BioPharma Group plc (NASDAQ: MREO) ("Mereo" or the "Company"), a clinical-stage biopharmaceutical company focused on rare diseases, reported financial results for the full year ended December 31, 2025, and provided an update on recent corporate developments.

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"In collaboration with our partner Ultragenyx, we have analysed a significant part of the data from the Phase 3 Orbit and Cosmic studies of setrusumab in osteogenesis imperfecta and continue to develop our understanding of the fracture data and the patient reported outcomes (PROs), especially in patients aged 2–18 years old. We believe that these data, which include pre-specified sub-groups and ad hoc analyses, may provide the basis for engagement with the regulatory agencies," said Denise Scots-Knight, Chief Executive Officer of Mereo. "There are no FDA or EMA therapies approved specifically for OI and although bisphosphonates are used to improved bone mineral density, it remains a high unmet need. Setrusumab has demonstrated statistically significant improvements in bone mineral density as well as compelling reductions in vertebral fractures and statistically significant improvements in PROs of disease pain and daily activity in pediatric and teenage patients. We look forward to providing updates on these efforts as we progress with next steps. Alongside this, our partnering discussions around alvelestat in AATD-LD are continuing to advance on multiple fronts and our partner āshibio has indicated that it plans to initiate a Phase 2 trial of vantictumab in osteopetrosis in the second half of this year. Following our cost reductions and delays to investment in manufacturing and pre-commercial activities for setrusumab, our revised financial runway into mid-2027 enables us to potentially deliver on several key milestones during 2026."

Setrusumab (UX143)

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As announced on December 29, 2025, the Phase 3 Orbit and Cosmic studies of setrusumab in OI did not achieve statistical significance against the primary endpoints of reduction in annualized clinical fracture rate compared to placebo or bisphosphonates, respectively.
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Both studies achieved high statistical significance against the key secondary endpoint of improvement in bone mineral density versus a placebo or versus a bisphosphonate (standard of care) comparator.
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The improvement in bone mineral density in the Cosmic study was associated with a decreased rate of fracture in this younger, more highly fracturing patient population, although this was not statistically significant.
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Additionally, the studies demonstrated reductions in vertebral fractures, which are a key contributor to pain and disability in this patient population and are known to drive treatment decisions, as well as improvements in patient-reported outcomes of disease severity, pain / comfort and daily activities which were statistically significant in the Orbit study in pediatrics and teens.
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The safety profile of setrusumab was consistent with that observed in prior studies.
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Further analyses of the data from both studies, including patient subgroups, are ongoing ahead of any planned interactions with the regulatory agencies.

Alvelestat (MPH-966)

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The site feasibility work for initiation of the global Phase 3 pivotal study has been completed.
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Based on previous discussions with the FDA and EMA, Mereo anticipates a single Phase 3 trial enrolling approximately 220 early- and late-stage AATD-LD patients evaluating alvelestat over an 18-month treatment period will support regulatory submissions in both the U.S. and Europe.
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The primary efficacy endpoint for potential U.S. approval will be the St. George’s Respiratory Questionnaire (SGRQ) Total Score, with lung density measured by CT scan serving as the primary endpoint for potential European regulatory approval.
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Mereo continues to be in active discussions with potential partners for the Phase 3 development and commercialization of alvelestat.
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Additionally, the Company has designed a potential Phase 2b study of alvelestat in bronchiectasis to further support the ongoing partnering discussions.

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The proposed study would enroll approximately 250 patients, randomized 1:1:1 to receive one of two alvelestat doses with standard of care or placebo with standard of care, with a primary efficacy endpoint of change in exacerbation rate at six months.
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The proposed trial design is intended to substantially de-risk potential Phase 3 development, as exacerbations are a required confirmatory endpoint in registrational trials.

Vantictumab (OMP18R5)

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The Company outlicensed vantictumab for autosomal dominant osteopetrosis Type 2 (ADO2) to āshibio, Inc. whilst retaining European rights.
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āshibio is responsible for funding the global program and, following regulatory discussions, plans to initiate a Phase 2 study in the second half of 2026.
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Vantictumab was previously investigated in Phase 1a/b oncology trials in around 100 patients with biomarker evidence of potential impact on osteoclast function and high bone turnover, which led to fragility fractures in some patients.
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āshibio reported promising pre-clinical data at ASBMR 2025 in an ADO2 mouse model, in which vantictumab significantly decreased areal bone mineral density and rescued the bone phenotype in this model.
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ADO2 is an inherited metabolic bone disorder characterized by impaired osteoclast function, with no currently approved therapies. This impaired osteoclast function results in the growth of dense, brittle bones leading to multiple fractures, osteomyelitis, bone pain, low blood counts and significant morbidity.

Full Year 2025 Financial Results

Total research and development ("R&D") expenses decreased by $3.2 million from $20.9 million in 2024 to $17.8 million in 2025. The decrease was primarily due to reductions in R&D expenses for alvelestat and etigilimab of $7.7 million and $1.0 million, respectively, partially offset by an increase of $5.7 million in R&D expenses for setrusumab. The reductions in program expenses for alvelestat was primarily due to the completion of the activities undertaken in preparation for the potential Phase 3 study, including drug formulation and manufacturing, in the year ended December 31, 2024. The increase in program expenses for setrusumab was primarily driven by amounts due under the manufacturing and supply agreement with our partner, Ultragenyx, as well as ongoing activities we undertake related to real-world evidence programs and medical affairs activities in Europe. These are in addition to costs we incur in relation to our collaboration with Ultragenyx, who fund the global development of the program, including input into development, regulatory and manufacturing plans.

General and administrative expenses decreased by $3.4 million from $26.4 million in 2024 to $23.0 million in 2025. The decrease was due to a lower accrual for annual cash bonuses of $1.2 million, along with a reduction in professional fees.

Net loss for the full year ended December 31, 2025, was $41.9 million, compared to $43.3 million during 2024, primarily reflecting an operating loss of $40.1 million and a foreign currency translation loss of $6.3 million, partially offset by interest income of $2.2 million and a benefit from research and development tax credit of $1.9 million.

As of December 31, 2025, the Company had cash and cash equivalents of $41.0 million, compared to $69.8 million as of December 31, 2024. The Company’s expects, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its operating expenses, and capital expenditure requirements into mid-2027. This guidance does not include any potential upfront payments associated with a partnership for alvelestat or business development activity around any of the Company’s non-core programs.

Total ordinary shares issued as of December 31, 2025 were 795,658,504. Total ADS equivalents as of December 31, 2025 were 159,131,700, with each ADS representing five ordinary shares of the Company.

(Press release, Mereo BioPharma, MAR 19, 2026, View Source [SID1234663749])