MREO

Entered into option and license agreement with Sentynl Therapeutics for alvelestat, Mereo’s investigational oral therapy for Alpha-1 Antitrypsin Deficiency-Associated Lung Disease (AATD-LD) Mereo and partner Ultragenyx engaging with regulatory agencies on potential path forward for setrusumab in osteogenesis imperfecta (OI); further updates expected by year-end 2026 Cash and cash equivalents of $30.1 million at June 30, 2026, now expected to fund operations into late-2027 LONDON, Aug. 11, 2026 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced financial results for the second quarter ended June 30, 2026, and provided an update on recent corporate highlights. The Company is also updating its previous cash runway guidance. As of June 30, 2026, cash and cash equivalents were approximately $30 million, which are expected to fund operations into late-2027. “The partnership with Sentynl Therapeutics which we announced earlier today marks a significant milestone for our alvelestat program and for the Company as a whole. We are now working together to refine the design of the global Phase 3 study for our potential first-in-class oral therapy for AATD-LD and look forward to a continued close collaboration during the short option period. Assuming exercise of the license option by Sentynl, we plan to initiate the Phase 3 trial in early 2027,” said Denise Scots-Knight, Chief Executive Officer of Mereo BioPharma. “Additionally, alongside our partner Ultragenyx, we have had initial regulatory interactions on setrusumab with the FDA and the MHRA and we expect to be in a position to provide an update on the potential path forward by the end of this year. We finished the quarter with approximately $30 million in cash. Thanks to our careful expense management, we now expect that this cash will provide runway into late-2027, exclusive of the potential $40 million in upfront and R&D payments that we are eligible to receive on exercise of the alvelestat option by Sentynl.” Second Quarter 2026 Highlights, Recent Developments, and Anticipated Milestones Setrusumab (UX143) The Orbit and the Cosmic Phase 3 studies did not achieve statistical significance against the primary endpoints of reduction in annualized clinical fracture rate, however, both achieved high statistical significance against the key secondary endpoint of improvement in bone mineral density, as well as reductions in vertebral fractures and improvements in patient reported outcomes (PROs) associated with disease severity, pain / discomfort and daily activities, with these PRO improvements achieving statistical significance in the Orbit study. Setrusumab also achieved meaningful reductions in fractures in certain bones and in patients with higher fracture frequencies. Both studies demonstrated a safety profile consistent with that observed in previous trials. Mereo and its partner, Ultragenyx Pharmaceutical, Inc. (Ultragenyx), are engaged with regulatory agencies to determine a potential path forward for setrusumab in pediatric OI patients and, to-date, have held discussions with the regulators in the U.S. and the U.K. The FDA indicated openness to considering alternative approaches to fracture analysis, with additional conversations needed to further define what additional clinical data would be needed to support a potential BLA. In recent communications with the MHRA, they encouraged further dialogue on any future development proposal, and we plan to have further interactions following the FDA discussions. Alvelestat (MPH-966) Mereo recently announced an option and license agreement with Sentynl Therapeutics, Inc. (Sentynl), a wholly owned subsidiary of Zydus Lifesciences Limited. Sentynl has the right to acquire a license for the U.S. commercial and global manufacturing rights to alvelestat for AATD-LD. Vantictumab (OMP18R5) āshibio, Inc. (āshibio), Mereo’s development and commercial partner for vantictumab, is continuing to advance toward initiation of a Phase 2 clinical trial in autosomal dominant osteopetrosis Type 2 (ADO2). āshibio is responsible for the global clinical development of vantictumab. Mereo has retained European commercial rights to the product, with āshibio holding commercial rights for the rest of the world. Second Quarter 2026 Financial Results Total research and development (“R&D”) expenses decreased by $3.6 million, from $5.4 million in the second quarter of 2025 to $1.8 million in the second quarter of 2026. The decrease was primarily due to a reduction of $2.6 million in R&D expenses for setrusumab and $1.0 million for alvelestat. The decrease in program expenses for setrusumab was primarily driven by reduction of, and delays to, investment in manufacturing and ongoing activities, including medical affairs activities in Europe during the second quarter of 2026. The decrease in program expenses for alvelestat was primarily due to completion of activities undertaken in preparation for the potential Phase 3 study during 2025. General and administrative (“G&A”) expenses decreased by $0.3 million, from $5.5 million in the second quarter of 2025 to $5.2 million in the second quarter of 2026. The decrease was primarily due to reductions of approximately $2.2 million driven by delays to investment in pre-commercial activities to lay the foundation for the potential commercial launch of setrusumab in Europe and other realized cost savings. These decreases were partially offset by the recognition of a $1.9 million reduction in expenses in the second quarter of 2025 for amounts received from our depository to reimburse certain expenses incurred by us in respect of our ADR program, whereas the corresponding amount in the current year was recognized in the first quarter of 2026. Net loss for the second quarter of 2026 was $7.0 million, compared to $14.6 million for the second quarter of 2025, primarily reflecting reductions in R&D and G&A expenses and a lower net foreign currency translation loss. As of June 30, 2026, the Company had cash and cash equivalents of $30.1 million, compared to $41.0 million as of December 31, 2025. The Company expects, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its currently committed clinical trials, operating expenses, and capital expenditure requirements into late 2027. This guidance does not include any future potential payments associated with business development activity around any of the Company’s programs. Total ordinary shares issued as of June 30, 2026 were 798,093,044. Total ADS equivalents as of June 30, 2026 were 159,618,608, with each ADS representing five ordinary shares of the Company. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has three rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); alvelestat for the treatment of alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD); and vantictumab for the treatment of autosomal dominant osteopetrosis type 2 (ADO2). The Company and its partner for setrusumab, Ultragenyx Pharmaceutical Inc., have reported top-line results from two Phase 3 studies for setrusumab in OI in patients aged 2 to 25 years old. Ultragenyx is funding and leading global development and Mereo has retained EU and UK commercial rights. Mereo has entered into an exclusive option and license agreement with Sentynl Therapeutics Inc. for the U.S. rights to commercialize alvelestat, while retaining rest of the world rights and will lead the global development. The agreement also grants Sentynl global rights to manufacture alvelestat for AATD-LD. Mereo has partnered with āshibio, Inc., for vantictumab in ADO2. āshibio, Inc. is funding and leading the global development program and Mereo has retained EU and UK commercial rights. Mereo has also entered into exclusive global license agreements with ReproNovo SA, for the development and commercialization of leflutrozole for the treatment of infertility in men, and with Feng Biosciences for the development and commercialization of navicixizumab for late-stage ovarian cancer. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties, as well as assumptions that, if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward-looking statements. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements reflect our current expectations, beliefs and assumptions concerning future events or our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Risks and uncertainties include, among other things, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the sufficiency of existing cash to fund operations and/or the inability to raise additional funding on favorable terms or at all; the uncertainty inherent in regulatory review processes, including varying interpretations and analyses of data from clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; potentially smaller than anticipated market opportunities for the Company's product candidates; the Company’s dependence on its key executives; and the Company’s ability to maintain compliance with Nasdaq continued listing requirements. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook,” “will,” “continue” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law.

LONDON, May 12, 2026 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced financial results for the first quarter ended March 31, 2026, and provided an update on recent corporate developments. “Based on extensive analysis of data across the two global Phase 3 studies of setrusumab in osteogenesis imperfecta in collaboration with our partner Ultragenyx, we believe there is basis to engage with the regulatory agencies to determine if there is a path forward in pediatric patients. These interactions have been initiated, and we plan to provide updates once we have some definitive feedback. We continue to believe that setrusumab has the potential to provide meaningful benefit for people living with OI, a condition with no FDA or EMA approved therapies,” said Denise Scots-Knight, Chief Executive Officer of Mereo. “We are engaged with potential partners for alvelestat in AATD-LD and believe alvelestat can quickly enter Phase 3 development following closing of a partnership transaction. Our other partnered program, vantictumab, is continuing to move forward with āshibio, who plan to initiate a Phase 2 trial in osteopetrosis in the second half of 2026. We continue to expect that our cash position, which totaled $36.2 million as of March 31, will provide runway into mid-2027, through several key inflection points expected during the remainder of this year.” Recent Corporate Developments and Anticipated Milestones Setrusumab (UX143) Further analyses of the data from the Orbit and Cosmic Phase 3 studies, including patient subgroups, have been completed. While neither study achieved statistical significance against the primary endpoints of reduction in annualized clinical fracture rate compared to placebo (Orbit) or bisphosphonates (Cosmic), both studies achieved high statistical significance against the key secondary endpoint of improvement in bone mineral density versus control as well as reductions in vertebral fractures and improvements in patient reported outcomes (PROs) associated with disease severity, pain / discomfort and daily activities, with these PRO improvements achieving statistical significance in the Orbit study. The safety profile of setrusumab was consistent with that observed in prior studies. Based on the Phase 3 data analysis from both global Phase 3 studies and the safety profile of setrusumab, Mereo and its partner Ultragenyx believe there is a basis to engage regulatory agencies to determine if there is a path forward for setrusumab in pediatric patients. These interactions have been initiated. Alvelestat (MPH-966) Mereo is actively engaged in discussions with potential partners for the Phase 3 development and commercialization of alvelestat. 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. 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. These are independent primary endpoints. The Company believes initiation of the Phase 3 study could happen within 6 months of closing a potential partnership transaction. Vantictumab (OMP18R5) The Company’s development partner for vantictumab, āshibio, Inc., is continuing to advance toward initiation of a Phase 2 clinical trial in autosomal dominant osteopetrosis Type 2 (ADO2), which is expected to commence in the second half of 2026. āshibio is responsible for funding the global clinical program and holds the right to commercialize vantictumab outside of Europe, where Mereo has retained commercial rights. First Quarter 2026 Financial Results Total research and development (“R&D”) expenses increased by $0.8 million, from $3.9 million in the first quarter of 2025 to $4.7 million in the first quarter of 2026. The increase was primarily due to increases of $1.8 million in R&D expenses for setrusumab, partially offset by reductions of $0.9 million in R&D expenses for alvelestat. The increase in program expenses for setrusumab was primarily driven by recognition of a payable for our share of certain costs related to the cancellation of manufacturing slots by our partner, Ultragenyx, partially offset by reductions of, and delays to, investment in manufacturing and ongoing activities, including medical affairs activities in Europe during the first quarter of 2026. The decrease in program expenses for alvelestat was primarily due to completion of activities undertaken in preparation for the potential Phase 3 study in the first quarter of 2025. General and administrative expenses decreased by $3.3 million, from $7.3 million in the first quarter of 2025 to $4.0 million in the first quarter of 2026. The decrease was primarily due to the recognition of a $1.9 million reduction in expenses in the first quarter of 2026 for amounts received from our depository to reimburse certain expenses incurred by us in respect of our ADR program, and a reduction of approximately $1.4 million driven by delays to investment in pre-commercial activities to lay the foundation for the potential commercial launch of setrusumab in Europe, if approved, and other realized cost savings. Net loss for the first quarter of 2026 was $6.7 million, compared to $12.9 million for the first quarter of 2025, primarily reflecting an operating loss of $8.8 million and foreign currency transaction gain of $1.6 million. As of March 31, 2026, the Company had cash and cash equivalents of $36.2 million, compared to $41.0 million as of December 31, 2025. The Company’s guidance remains unchanged, and it continues to expect, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its currently committed clinical trials, operating expenses, and capital expenditure requirements into mid-2027. This guidance does not include any potential payments associated with business development activity around any of the Company’s programs. Total ordinary shares issued as of March 31, 2026 were 798,078,829. Total ADS equivalents as of March 31, 2026 were 159,615,765, with each ADS representing five ordinary shares of the Company. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has three rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); alvelestat for the treatment of alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD); and vantictumab for the treatment of autosomal dominant osteopetrosis type 2 (ADO2). The Company and its partner for setrusumab, Ultragenyx Pharmaceutical Inc., have reported top-line results from the Phase 3 portion of a pivotal Phase 2/3 study in pediatrics and young adults (5 to 25 years old) and in the Phase 3 study in pediatric patients (2 to <7 years old) for setrusumab in OI. The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the European Commission (“EC”) and the FDA, PRIME designation from the EMA, and has Breakthrough Therapy designation and rare pediatric disease designation from the FDA. Alvelestat has received Orphan Designation for AATD from the EC and the FDA, and Fast Track designation from the FDA for AATD-LD. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the primary endpoints for a Phase 3 pivotal study which, if successful, could enable full approval in both the U.S. and Europe. The Company’s partner for vantictumab, āshibio, Inc., is funding the global development program and Mereo has retained EU and UK commercial rights. Mereo has also entered into an exclusive global license agreement with ReproNovo SA, a reproductive medicine company, for the development and commercialization of leflutrozole, a non-steroidal aromatase inhibitor for the treatment of infertility in men with low testosterone. In addition, Mereo has two oncology product candidates, etigilimab, an anti-TIGIT; and navicixizumab for the potential treatment of late-line ovarian cancer. Navicixizumab has been partnered with Feng Biosciences, Inc. in a global licensing agreement that includes milestone payments and royalties. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties, as well as assumptions that, if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward-looking statements. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements reflect our current expectations, beliefs and assumptions concerning future events or our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Risks and uncertainties include, among other things, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the sufficiency of existing cash to fund operations and/or the inability to raise additional funding on favorable terms or at all; the uncertainty inherent in regulatory review processes, including varying interpretations and analyses of data from clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; potentially smaller than anticipated market opportunities for the Company's product candidates; the Company’s dependence on its key executives; and the Company’s ability to maintain compliance with Nasdaq continued listing requirements. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook,” “will,” “continue” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law.

Additional data analyses from Orbit and Cosmic Phase 3 studies of setrusumab (UX143) in osteogenesis imperfecta ongoing Cash of $41.0 million as of December 31, 2025, expected to provide runway into mid-2027 LONDON, March 19, 2026 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced financial results for the full year ended December 31, 2025, and provided an update on recent corporate developments. “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) 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. 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. 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. 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. The safety profile of setrusumab was consistent with that observed in prior studies. 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) The site feasibility work for initiation of the global Phase 3 pivotal study has been completed. 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. 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. Mereo continues to be in active discussions with potential partners for the Phase 3 development and commercialization of alvelestat. Additionally, the Company has designed a potential Phase 2b study of alvelestat in bronchiectasis to further support the ongoing partnering discussions. 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. 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) The Company outlicensed vantictumab for autosomal dominant osteopetrosis Type 2 (ADO2) to āshibio, Inc. whilst retaining European rights. 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. 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. 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. 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. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has three rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); alvelestat for the treatment of alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD); and vantictumab for the treatment of autosomal dominant osteopetrosis type 2 (ADO2). The Company and its partner for setrusumab, Ultragenyx Pharmaceutical Inc., have reported top-line results from the Phase 3 portion of a pivotal Phase 2/3 study in pediatrics and young adults (5 to 25 years old) and in the Phase 3 study in pediatric patients (2 to <7 years old) for setrusumab in OI. The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the European Commission (“EC”) and the FDA, PRIME designation from the EMA, and has Breakthrough Therapy designation and rare pediatric disease designation from the FDA. Alvelestat has received Orphan Designation for AATD from the EC and the FDA, and Fast Track designation from the FDA for AATD-LD. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the primary endpoints for a Phase 3 pivotal study which, if successful, could enable full approval in both the U.S. and Europe. The Company’s partner for vantictumab, āshibio, Inc., is funding the global development program and Mereo has retained EU and UK commercial rights. Mereo has also entered into an exclusive global license agreement with ReproNovo SA, a reproductive medicine company, for the development and commercialization of leflutrozole, a non-steroidal aromatase inhibitor for the treatment of infertility in men with low testosterone. In addition, Mereo has two oncology product candidates, etigilimab, an anti-TIGIT; and navicixizumab for the potential treatment of late-line ovarian cancer. Navicixizumab has been partnered with Feng Biosciences, Inc. in a global licensing agreement that includes milestone payments and royalties. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties, as well as assumptions that, if they never materialize or prove incorrect, could cause our results to differ materially from those expressed or implied by such forward-looking statements. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements reflect our current expectations, beliefs and assumptions concerning future events or our future financial performance and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Risks and uncertainties include, among other things, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the sufficiency of existing cash to fund operations and/or the inability to raise additional funding on favorable terms or at all; the uncertainty inherent in regulatory review processes, including varying interpretations and analyses of data from clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; potentially smaller than anticipated market opportunities for the Company's product candidates; the Company’s dependence on its key executives; and the Company’s ability to maintain compliance with Nasdaq continued listing requirements. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook,” “will,” “continue” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law.

Data from Phase 3 Orbit and Cosmic studies of setrusumab in osteogenesis imperfecta on-track for around the end of 2025 Cash of $48.7 million as of September 30, 2025, expected to support operations into 2027 LONDON, Nov. 10, 2025 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced its financial results for the third quarter ended September 30, 2025, and provided recent corporate highlights. “We are rapidly approaching a major transition period in our corporate evolution, with the Phase 3 Orbit and Cosmic studies of setrusumab in osteogenesis imperfecta on track to read out around the end of the year. Based on the data from prior studies, we remain confident in the potential of setrusumab to reduce fractures and improve quality of life for people with OI. We continue to invest in commercial readiness activities to ensure Mereo is well positioned for a potential launch in our European territories,” said Dr. Denise Scots-Knight, Chief Executive Officer of Mereo. “Alongside the progress of the setrusumab program, we are continuing to advance partnering discussions for alvelestat. In addition, we are excited to have retained European commercial rights in our recent partnership deal with āshibio for vantictumab, which is being investigated in autosomal dominant osteopetrosis type 2, another rare bone disease for which promising preclinical data were presented at this year’s ASBMR Annual Meeting. With $48.7 million of cash at the end of the third quarter, we remain well-capitalized to continue executing through these important milestones.” Third Quarter 2025 Highlights, Recent Developments, and Anticipated Milestones Setrusumab (UX143) for osteogenesis imperfecta (OI) The Phase 3 Orbit and Cosmic studies, led by our partner Ultragenyx, evaluating setrusumab in pediatric and young adult patients and young pediatric patients with OI, are progressing towards final analyses at which time patients will have been on therapy for at least 18 months. The data from both Orbit and Cosmic are expected around the end of 2025. The threshold for the Phase 3 Orbit final analysis is p<0.039 and the threshold for the Phase 3 Cosmic final analysis is p<0.05. Pre-commercial efforts continue in Europe where Mereo holds commercial rights. These include continuation of the SATURN program and an expansion of the activities to determine the potential addressable market and identify treatment centers beyond the five major countries in Europe to the Nordic and Benelux regions. Alvelestat (MPH-966) for alpha-1-anti-trypsin deficiency lung disease (AATD-LD) Activities to support initiation of the planned single, global Phase 3 pivotal study are ongoing. The Company continues to be actively engaged with multiple potential partners regarding development and commercialization of alvelestat. Vantictumab for autosomal dominant osteopetrosis type 2 (ADO2) Vantictumab is a fully-human monoclonal antibody that binds to certain frizzled receptors and inhibits Wnt signaling pathways, which was previously being developed in oncology settings. Mereo granted āshibio, Inc. an exclusive license to develop vantictumab in ADO2. Under the agreement, announced in August 2025, Mereo has retained European commercial rights, and has granted āshibio the right to commercialize in the U.S. and rest of the world. Third Quarter 2025 Financial Results Total research and development (“R&D”) expenses increased by $1.1 million, from $3.2 million in the third quarter of 2024 to $4.3 million in the three months ended September 30, 2025. The increase was primarily due to increases of $0.9 million in R&D expenses for setrusumab and $0.5 million for alvelestat, partially offset by a reduction of $0.2 million in R&D expenses for etigilimab. 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 related to real-world evidence programs and medical affairs activities in Europe. This is 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. The increase in program expenses for alvelestat was primarily due to activities undertaken in preparation for the Phase 3 study, including drug product and packaging, in the three months ended September 30, 2025. General and administrative (“G&A”) expenses decreased by $0.2 million, from $6.2 million in the third quarter of 2024 to $6.0 million in the third quarter of 2025. The decrease was primarily due to lower professional fees. Net loss for the third quarter of 2025 was $7.0 million compared to $15.0 million for the third quarter of 2024, primarily reflecting an operating loss of $10.0 million and a foreign currency transaction gain of $1.9 million. As of September 30, 2025, the Company had cash and cash equivalents of $48.7 million, compared to $69.8 million as of December 31, 2024. The Company’s guidance remains unchanged, and it continues to expect, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its currently committed clinical trials, operating expenses, and capital expenditure requirements into 2027. This guidance does not include any payments associated with a potential partnership for alvelestat or business development activity around any of the Company’s non-core programs. Total ordinary shares issued as of September 30, 2025, were 795,484,404. Total ADS equivalents as of September 30, 2025, were 159,096,880, with each ADS representing five ordinary shares of the Company. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has three rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); alvelestat for the treatment of alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD) and vantictumab for the treatment of autosomal dominant osteopetrosis type 2 (ADO2). The Company’s partner for setrusumab, Ultragenyx Pharmaceutical, Inc., has completed enrollment in the Phase 3 portion of a pivotal Phase 2/3 study in pediatrics and young adults (5 to 25 years old) for setrusumab in OI and in the Phase 3 study in pediatric patients (2 to <7 years old). The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the European Commission (“EC”) and the FDA, PRIME designation from the EMA, and has Breakthrough Therapy designation and rare pediatric disease designation from the FDA. Alvelestat has received Orphan Designation for AATD from the EC and the FDA, and Fast Track designation from the FDA for AATD-LD. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the primary endpoints for a Phase 3 pivotal study which, if successful, could enable full approval in both the U.S. and Europe. The Company’s partner for vantictumab, āshibio, Inc., is funding the global development program. Mereo has retained EU and UK commercial rights. Mereo has also entered into an exclusive global license agreement with ReproNovo SA, a reproductive medicine company, for the development and commercialization of leflutrozole, a non-steroidal aromatase inhibitor for the treatment of infertility in men with low testosterone. In addition, Mereo has two oncology product candidates, etigilimab, an anti-TIGIT; and navicixizumab for the potential treatment of late-line ovarian cancer. Navicixizumab has been partnered with Feng Biosciences, Inc. in a global licensing agreement that includes milestone payments and royalties. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements usually relate to future events and anticipated revenues, earnings, cash flows or other aspects of our operations or operating results. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. All of the Company’s forward-looking statements involve known and unknown risks and uncertainties some of which are significant or beyond its control and assumptions that could cause actual results to differ materially from the Company’s historical experience and its present expectations or projections. Such risks and uncertainties include, among others, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; and the Company’s dependence on its key executives. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law. Mereo BioPharma Contacts:

Data from Phase 3 Orbit and Cosmic studies of setrusumab in osteogenesis imperfecta expected around year-end 2025 Cash of $56.1 million as of June 30, 2025, expected to support operations into 2027 LONDON, Aug. 12, 2025 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced its financial results for the second quarter ended June 30, 2025, and provided recent corporate highlights. “We look forward to the final analysis for the two ongoing Phase 3 studies for setrusumab in osteogenesis imperfecta, the Phase 3 Orbit study in pediatric and young adult patients, and the Phase 3 Cosmic study in young pediatric patients, around the end of the year. We continue to be excited about the potential of setrusumab to reduce fractures and improve other functional parameters for individuals living with osteogenesis imperfecta,” said Dr. Denise Scots-Knight, Chief Executive Officer of Mereo. “In parallel with the advancement of setrusumab, we are continuing to advance partnering discussions around alvelestat, our first-in-class oral small molecule for AATD-lung disease, and to ready the program for Phase 3 initiation. Our prudent management of our cash and resources means we are well positioned through these key milestones to support our operations into 2027.” Second Quarter 2025 Highlights, Recent Developments, and Anticipated Milestones Setrusumab (UX143) for osteogenesis imperfecta (OI) The Phase 3 Orbit and Cosmic studies, led by our partner Ultragenyx, evaluating setrusumab in pediatric and young adult patients and young pediatric patients with OI, are progressing towards their final analyses around the end of 2025. The randomized, placebo-controlled Phase 3 portion of the Orbit study was evaluated by the Data Monitoring Committee at an interim analysis in July 2025 and they informed Ultragenyx that setrusumab demonstrated an acceptable safety profile and that the study should continue to the final analysis. Data from the Cosmic study were not analyzed at the interim timepoint, consistent with the statistical analysis plan. Patients will continue dosing in both the Phase 3 Orbit and Cosmic studies, with the final analyses to be conducted after patients have been on therapy for at least 18-months. The threshold for the Phase 3 Orbit final analysis is p<0.04 and for the Phase 3 Cosmic final analysis is p<0.05. Pre-commercial efforts continue in Europe where Mereo holds commercial rights. These include continuation of the SATURN program, working with existing OI datasets to better understand the natural history and the unmet medical need in pediatrics and adults and to generate data to support the health economic model, both important to support the assessment by Regulatory and Health Technology Assessment (HTA) bodies and payors. In addition, the activities to define the treatment landscape, including the number of treatment centers and the patient journey from childhood to adulthood, are being extended beyond the five major countries in Europe. Alvelestat (MPH-966) for alpha-1-anti-trypsin deficiency lung disease (AATD-LD) Activities to support initiation of the planned single, global Phase 3 pivotal study are ongoing. The Company continues to be actively engaged with multiple potential partners regarding development and commercialization of alvelestat. Second Quarter 2025 Financial Results Total research and development (“R&D”) expenses increased by $0.4 million from $4.9 million in the three months ended June 30, 2024, to $5.4 million in the three months ended June 30, 2025. The increase was primarily due to increases of $2.2 million in R&D expenses for setrusumab offset by decreases of $1.5 million and $0.2 million in R&D expenses for alvelestat and etigilimab, respectively. 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 related to real-world evidence programs and medical affairs activities in Europe. This is 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. The decrease in program expenses for alvelestat was primarily due to the completion of the drug formulation and manufacturing activities undertaken in preparation for the Phase 3 study in the three months ended June 30, 2024. General and administrative (“G&A”) expenses decreased by $2.4 million from $7.9 million in the second quarter of 2024 to $5.5 million in the second quarter of 2025. The decrease was primarily due to the recognition of a $1.9 million reduction in expenses in the three months ended June 30, 2025 for amounts received from our depository to reimburse certain expenses incurred by us in respect of our ADR program as well as lower professional fees. Net loss for the second quarter ended June 30, 2025 was $14.6 million, compared to $12.3 million during the comparable period in 2024, primarily reflecting a foreign currency transaction loss of $5.4 million and increases in R&D expenses, offset by a decrease in G&A expenses and $0.5 million in revenue from a one-time milestone payment for the achievement of a clinical milestone on leflutrozole. As of June 30, 2025, the Company had cash and cash equivalents of $56.1 million, compared to $69.8 million as of December 31, 2024. The Company’s guidance remains unchanged, and it continues to expect, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its currently committed clinical trials, operating expenses, and capital expenditure requirements into 2027. This guidance does not include any payments associated with a potential partnership for alvelestat or business development activity around any of the Company’s non-core programs. Total ordinary shares issued as of June 30, 2025, were 795,001,444. Total ADS equivalents as of June 30, 2025, were 159,000,288, with each ADS representing five ordinary shares of the Company. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has two rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); and alvelestat for the treatment of alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD). The Company’s partner, Ultragenyx Pharmaceutical, Inc., has completed enrollment in the Phase 3 portion of a pivotal Phase 2/3 study in pediatrics and young adults (5 to 25 years old) for setrusumab in OI and in the Phase 3 study in pediatric patients (2 to <7 years old). The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the European Commission (“EC”) and the FDA, PRIME designation from the EMA, and has Breakthrough Therapy designation and rare pediatric disease designation from the FDA. Alvelestat has received Orphan Designation for AATD from the EC and the FDA, and Fast Track designation from the FDA for AATD-LD. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the primary endpoints for a Phase 3 pivotal study which, if successful, could enable full approval in both the U.S. and Europe. Mereo has also entered into an exclusive global license agreement with ReproNovo SA, a reproductive medicine company, for the development and commercialization of leflutrozole, a non-steroidal aromatase inhibitor for the treatment of infertility in men with low testosterone. In addition, Mereo has two oncology product candidates, etigilimab, an anti-TIGIT; and navicixizumab for the potential treatment of late-line ovarian cancer. Navicixizumab has been partnered with Feng Biosciences, Inc. in a global licensing agreement that includes milestone payments and royalties. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements usually relate to future events and anticipated revenues, earnings, cash flows or other aspects of our operations or operating results. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. All of the Company’s forward-looking statements involve known and unknown risks and uncertainties some of which are significant or beyond its control and assumptions that could cause actual results to differ materially from the Company’s historical experience and its present expectations or projections. Such risks and uncertainties include, among others, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; and the Company’s dependence on its key executives. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law.

Progress continues in Phase 3 Orbit study of setrusumab in osteogenesis imperfecta (OI) Cash of $62.5 million as of March 31, 2025, expected to fund operations into 2027 LONDON, May 13, 2025 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced its financial results for the first quarter ended March 31, 2025, and provided recent corporate highlights. “As we close out the first quarter of 2025, we continue to anticipate that this will be an important, milestone-rich year for Mereo. The Phase 3 Orbit study of setrusumab in osteogenesis imperfecta remains on track to read-out either at the second interim analysis in mid-2025 or at the final analysis in the fourth quarter. We are continuing to invest in the pre-commercial activities for setrusumab to enable a successful launch in our European territory, following potential regulatory approvals,” said Dr. Denise Scots-Knight, Chief Executive Officer of Mereo. "Further, alvelestat is now Phase 3 ready and we are finalizing the trial start-up activities to support our ongoing partnering process. Along with our late-stage pipeline, we believe that continued close management of our cash balance will enable us to support our operations into 2027.” First Quarter 2025 Highlights, Recent Developments, and Anticipated Milestones Setrusumab (UX143) Continued progress in the two global Phase 3 studies led by our partner Ultragenyx: The randomized, placebo-controlled Phase 3 portion of the Orbit study (in patients aged 5 to 25 years) is progressing toward the second interim analysis (IA2) in mid-2025 or a final analysis in the fourth quarter of 2025. All patients have now been on therapy for at least 12 months, conduct of the study is going well and patient safety in the Phase 3 portion of the study is consistent with safety observed in the Phase 2. Patients in the Cosmic study (aged 2 to <7 years) are being treated with either setrusumab or intravenous bisphosphonates (IV-BP) therapy and will be evaluated in parallel with the Orbit interim analysis. If Orbit progresses to full study completion in the fourth quarter of 2025, Cosmic will also continue to a data readout, to align with the Orbit readout without spending alpha at the mid-year interim assessment. Continued pre-commercial activities in Europe to support potential launch, including engagement with regulatory/HTA bodies and real-world data collection efforts through the SATURN program. Alvelestat (MPH-966) In the first quarter of 2025, the European Commission granted Orphan Designation to alvelestat for the treatment of alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD). This adds to existing US FDA Orphan Drug and Fast Track designations. The start-up activities for the planned single, global Phase 3 pivotal study are ongoing. The Company remains in discussion with multiple potential development and commercialization partners. First Quarter 2025 Financial Results Total research and development (“R&D”) expenses decreased by $0.1 million from $4.0 million in the first quarter of 2024 to $3.9 million in the first quarter of 2025. The decrease was primarily due to decreases of $1.2 million and $0.1 million in R&D expenses for alvelestat and etigilimab, offset by an increase of $1.3 million in R&D expenses for setrusumab. The decrease in program expenses for alvelestat was primarily due to undertaking reduced drug formulation and manufacturing activities in preparation for the Phase 3 study in the first quarter of 2025, compared to the first quarter of 2024. The increase in program expenses for setrusumab was primarily driven by amounts due under the manufacturing and supply agreement with our partner, Ultragenyx, ongoing activities related to real-world evidence programs and medical affairs activities in Europe and input into development, regulatory and manufacturing plans with Ultragenyx, who fund the global development of the program pursuant to our license and collaboration agreement. General and administrative expenses increased by $1.4 million from $5.9 million in the first quarter of 2024 to $7.3 million in the first quarter of 2025. The increase was primarily due to the recognition of a $1.7 million reduction in expenses in the first quarter of 2024 for amounts received from our depository to reimburse certain expenses incurred by us in respect of our ADR program, partially offset by a net decrease in employee-related expenses and professional fees. A reimbursement in respect of our ADR program is anticipated in 2025. Net loss for the first quarter of 2025 was $12.9 million, compared to $9.0 million during the first quarter of 2024, primarily reflecting an operating loss of $11.2 million and foreign currency translation loss. As of March 31, 2025, the Company had cash and cash equivalents of $62.5 million, compared to $69.8 million as of December 31, 2024. The Company’s guidance remains unchanged, and it continues to expect, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its currently committed clinical trials, operating expenses, and capital expenditure requirements into 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 March 31, 2025 were 795,001,444. Total ADS equivalents as of March 31, 2025 were 159,000,288, with each ADS representing five ordinary shares of the Company. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has two rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); and alvelestat for the treatment of severe alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD). The Company’s partner, Ultragenyx Pharmaceutical, Inc., has completed enrollment in the Phase 3 portion of a pivotal Phase 2/3 study in pediatrics and young adults (5 to 25 years old) for setrusumab in OI and in the Phase 3 study in pediatric patients (2 to <7 years old). The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the European Commission (“EC”) and the FDA, PRIME designation from the EMA, and has Breakthrough Therapy designation and rare pediatric disease designation from the FDA. Alvelestat has received Orphan Designation for AATD from the EC and the FDA, and Fast Track designation from the FDA for AATD-LD. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the primary endpoints for a Phase 3 pivotal study which, if successful, could enable full approval in both the U.S. and Europe. In addition to the rare disease programs, Mereo has two oncology product candidates, etigilimab, an anti-TIGIT; and navicixizumab for the potential treatment of late-line ovarian cancer. Navicixizumab has been partnered with Feng Biosciences, Inc. in a global licensing agreement that includes milestone payments and royalties. Mereo has also entered into an exclusive global license agreement with ReproNovo SA, a reproductive medicine company, for the development and commercialization of leflutrozole, a non-steroidal aromatase inhibitor. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements usually relate to future events and anticipated revenues, earnings, cash flows or other aspects of our operations or operating results. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. All of the Company’s forward-looking statements involve known and unknown risks and uncertainties some of which are significant or beyond its control and assumptions that could cause actual results to differ materially from the Company’s historical experience and its present expectations or projections. Such risks and uncertainties include, among others, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; and the Company’s dependence on its key executives. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law. Mereo BioPharma Contacts:

Orbit Phase 3 study of setrusumab in osteogenesis imperfecta progressing toward second interim analysis, expected mid-2025 Alvelestat granted Orphan Designation by the European Commission for treatment of Alpha-1 Antitrypsin Deficiency-associated Lung Disease (AATD-LD) Cash of $69.8 million as of December 31, 2024, expected to fund operations into 2027 LONDON, March 26, 2025 (GLOBE NEWSWIRE) -- Mereo BioPharma Group plc (NASDAQ: MREO) (“Mereo” or the “Company”), a clinical-stage biopharmaceutical company focused on rare diseases, today announced its financial results for the full year ended December 31, 2024, and provided recent corporate highlights. “2024 was a year of focused execution and strategic advancement at Mereo, driving our lead programs closer to key milestones," said Dr. Denise Scots-Knight, Chief Executive Officer of Mereo. "The Phase 3 Orbit study of setrusumab in osteogenesis imperfecta (OI) is set to read out at the upcoming second interim analysis mid-year or at the final analysis during the fourth quarter of 2025. This could set the stage for us, alongside our partner Ultragenyx, to file for regulatory approvals in the U.S. and EU. Our European pre-commercial activities are ongoing, where we are focused on laying the foundation for a successful and efficient commercial launch, following potential regulatory approval. On alvelestat, the recent receipt of European Orphan Designation and the Phase 3 readiness activities have been highly supportive for our ongoing partnering process. With a strong financial position, we look forward to a transformative 2025, focused on bringing life-changing therapies to patients with rare diseases.” 2024 Highlights, Recent Developments, and 2025 Anticipated Milestones Setrusumab (UX143) Continued progress in two global studies, the Phase 3 portion of Orbit (Phase 2/3) and Cosmic (Phase 3), of setrusumab in OI patients, led by our partner Ultragenyx. The Phase 3 portion of the Orbit Study is continuing to dose pediatric and young adult patients, with the second interim analysis expected mid-2025 and potential final analysis in the fourth quarter of 2025. Treatment is ongoing in the open-label Phase 3 Cosmic study evaluating setrusumab against intravenous bisphosphonate therapy in patients aged 2 to <7 years. Data from this study will be evaluated in parallel with the interim or final analysis from the Orbit study. Pre-commercial activities to lay the foundation for launch ongoing. Scientific advice obtained from GBA in Germany and NICE in the U.K. Progress on project SATURN with existing registries that are appropriate sources of data on the natural history of OI and longitudinal data with the standard-of-care. Alvelestat (MPH-966) In the first quarter of 2025, the European Commission granted Orphan Designation to alvelestat for the treatment of AATD-LD. This designation followed a positive recommendation from the EMA Committee for Orphan Medicinal Products in January 2025. Alvelestat previously received Orphan Drug Designation and Fast Track Designation from the U.S. FDA in 2021 and 2022, respectively. The Company remains in discussion with multiple potential partners for the development and commercialization of alvelestat. Full Year 2024 Financial Results Total research and development (“R&D”) expenses increased by $3.5 million from $17.4 million in 2023 to $20.9 million in 2024. The increase was primarily due to increases of $6.2 million and $2.6 million in R&D expenses for alvelestat and setrusumab, respectively, partially offset by a $5.5 million decrease in R&D expenses for etigilimab. The increase in program expenses for alvelestat is due to the preparatory work for the Phase 3 study. This principally comprised drug formulation and manufacturing activities, SGRQ validation activities and regulatory interactions. The increase in program expenses for setrusumab was primarily due to higher levels of ongoing activities in Europe, including real-world evidence programs and medical affairs activities, and amounts under the manufacturing and supply agreement with our partner, Ultragenyx, along with input into development, regulatory and manufacturing plans with Ultragenyx, who fund the global development of the program pursuant to our license and collaboration agreement. The reduction in program expenses for etigilimab was primarily due to the winding down and completion of the open label Phase 1b/2 basket study in combination with an anti-PD-1 in a range of tumor types. General and administrative expenses increased by $8.0 million from $18.4 million in 2023 to $26.4 million in 2024. The increase primarily reflects $2.7 million higher pre-commercial activities to lay the foundation for the commercial launch of setrusumab in Europe, including activities to support pricing and reimbursement by HTA authorities and payor decision-makers in Europe. The remaining increase is driven by additional corporate expenses, including employee-related costs and legal and professional fees in respect of compliance with the U.S. domestic reporting regime, and reductions in reimbursements of certain expenses from our depository in respect of our ADR program and settlement of a claim under our D&O insurance policy in the prior year. Net loss for the full year ended December 31, 2024 was $43.3 million, compared to $29.5 million during the comparable period in 2023, primarily reflecting an operating loss of $47.4 million, partially offset by interest income and the benefit from R&D tax credits. As of December 31, 2024, the Company had cash and cash equivalents of $69.8 million, compared to $57.4 million as of December 31, 2023. The Company’s guidance remains unchanged, and it continues to expect, based on current operational plans, that its existing cash and cash equivalents balance will enable it to fund its currently committed clinical trials, operating expenses, and capital expenditure requirements into 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, 2024 were 775,728,034. Total ADS equivalents as of December 31, 2024 were 155,145,606, with each ADS representing five ordinary shares of the Company. About Mereo BioPharma Mereo BioPharma is a biopharmaceutical company focused on the development of innovative therapeutics for rare diseases. The Company has two rare disease product candidates: setrusumab for the treatment of osteogenesis imperfecta (OI); and alvelestat for the treatment of severe alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD). The Company’s partner, Ultragenyx Pharmaceutical, Inc., has completed enrollment in the Phase 3 portion of a pivotal Phase 2/3 study in pediatrics and young adults (5 to 25 years old) for setrusumab in OI and in the Phase 3 study in pediatric patients (2 to <7 years old). The partnership with Ultragenyx includes potential additional milestone payments of up to $245 million and royalties to Mereo on commercial sales in Ultragenyx territories. Mereo has retained EU and UK commercial rights and will pay Ultragenyx royalties on commercial sales in those territories. Setrusumab has received orphan designation for osteogenesis imperfecta from the European Commission (“EC”) and the FDA, PRIME designation from the EMA, and has Breakthrough Therapy designation and rare pediatric disease designation from the FDA. Alvelestat has received Orphan Designation for AATD from the EC and the FDA, and Fast Track designation from the FDA for AATD-LD. Following results from ASTRAEUS and ATALANTa in AATD-lung disease, the Company has aligned with the FDA and the EMA on the primary endpoints for a Phase 3 pivotal study which, if successful, could enable full approval in both the U.S. and Europe. In addition to the rare disease programs, Mereo has two oncology product candidates, etigilimab, an anti-TIGIT; and navicixizumab for the potential treatment of late-line ovarian cancer. Navicixizumab has been partnered with Feng Biosciences, Inc. in a global licensing agreement that includes milestone payments and royalties. Mereo has also entered into an exclusive global license agreement with ReproNovo SA, a reproductive medicine company, for the development and commercialization of leflutrozole, a non-steroidal aromatase inhibitor. Forward-Looking Statements This press release contains “forward-looking statements” that involve substantial risks and uncertainties. All statements other than statements of historical fact contained herein are forward-looking statements within the meaning of Section 27A of the United States Securities Act of 1933, as amended, and Section 21E of the United States Securities Exchange Act of 1934, as amended. Forward-looking statements usually relate to future events and anticipated revenues, earnings, cash flows or other aspects of our operations or operating results. Forward-looking statements are often identified by the words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “may,” “estimate,” “outlook” and similar expressions, including the negative thereof. The absence of these words, however, does not mean that the statements are not forward-looking. These forward-looking statements are based on the Company’s current expectations, beliefs and assumptions concerning future developments and business conditions and their potential effect on the Company. While management believes that these forward-looking statements are reasonable as and when made, there can be no assurance that future developments affecting the Company will be those that it anticipates. All of the Company’s forward-looking statements involve known and unknown risks and uncertainties some of which are significant or beyond its control and assumptions that could cause actual results to differ materially from the Company’s historical experience and its present expectations or projections. Such risks and uncertainties include, among others, the uncertainties inherent in the clinical development process; the Company’s reliance on third parties to conduct and provide funding for its clinical trials; the Company’s dependence on enrollment of patients in its clinical trials; and the Company’s dependence on its key executives. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the Company’s business, including those described in the “Risk Factors” section of its Annual Report on Form 10-K, as well as discussions of potential risks, uncertainties, and other important factors in the Company’s subsequent filings with the Securities and Exchange Commission. The Company wishes to caution you not to place undue reliance on any forward-looking statements, which speak only as of the date hereof. The Company undertakes no obligation to publicly update or revise any of our forward-looking statements after the date they are made, whether as a result of new information, future events or otherwise, except to the extent required by law. Mereo BioPharma Contacts: