Mereo BioPharma Shares Plunge 87.5% After Phase 3 Study Fails to Meet Primary Endpoints
Written by Emily J. Thompson, Senior Investment Analyst
Updated: Dec 29 2025
0mins
Should l Buy MREO?
Source: Benzinga
- Study Failure: Mereo BioPharma's Phase 3 ORBIT and COSMIC studies failed to achieve statistical significance in reducing clinical fracture rates, causing shares to plummet 87.5% to $0.29 in pre-market trading, severely undermining market confidence in the company.
- Partner Impact: Ultragenyx Pharmaceutical, a partner of Mereo, also saw its shares drop 43.7% to $19.26, reflecting investor pessimism about the drug's prospects, which may affect future collaborations and funding for research and development.
- Market Reaction: Other related stocks, such as SPAC III Acquisition Corp and Sellas Life Sciences, experienced declines of 11.7% and 7.6%, respectively, indicating a broader erosion of confidence in the biotech sector among investors.
- Investor Sentiment: The failure of Mereo's studies has dampened investor sentiment in the biotech field, potentially leading to capital outflows and stricter financing conditions that could hinder the growth of other companies in the industry.
Trade with 70% Backtested Accuracy
Stop guessing "Should I Buy MREO?" and start using high-conviction signals backed by rigorous historical data.
Sign up today to access powerful investing tools and make smarter, data-driven decisions.
Analyst Views on MREO
Wall Street analysts forecast MREO stock price to rise
8 Analyst Rating
6 Buy
2 Hold
0 Sell
Strong Buy
Current: 0.386
Low
0.50
Averages
2.08
High
5.00
Current: 0.386
Low
0.50
Averages
2.08
High
5.00
About MREO
Mereo BioPharma Group plc is a biopharmaceutical company focused on the development of therapeutics for rare diseases. The Company has developed a portfolio of late-stage clinical product candidates, and its two rare disease product candidates are setrusumab for the treatment of osteogenesis imperfecta (OI) and alvelestat primarily for the treatment of severe alpha-1 antitrypsin deficiency-associated lung disease (AATD-LD). In addition to the rare disease programs, it has two oncology product candidates in clinical development, which include Etigilimab, an IgG1 monoclonal antibody which binds to the human T-cell immunoreceptor with Ig and ITIM domains (TIGIT) receptor on immune cells to improve the activation and effectiveness of T-cell and NK cell antitumor activity and Navicixizumab is a bispecific antibody that inhibits delta-like ligand 4 (DLL4) and vascular endothelial growth factor (VEGF). Navicixizumab is developed for the treatment of late-line ovarian cancer.
About the author
Emily J. Thompson
Emily J. Thompson, a Chartered Financial Analyst (CFA) with 12 years in investment research, graduated with honors from the Wharton School. Specializing in industrial and technology stocks, she provides in-depth analysis for Intellectia’s earnings and market brief reports.
Class Action Filed Against Mereo BioPharma Group plc
- Lawsuit Background: Bronstein, Gewirtz & Grossman LLC has filed a class action lawsuit against Mereo BioPharma Group plc, alleging violations of federal securities laws on behalf of all investors who purchased Mereo securities between June 5, 2023, and December 26, 2025.
- False Statements Allegation: The complaint claims that throughout the class period, defendants made overwhelmingly positive statements while disseminating materially false and misleading information, concealing adverse facts about the Phase 3 ORBIT and COSMIC programs, both of which failed to meet their primary endpoints for reducing clinical fracture rates.
- Investor Action: Affected investors are encouraged to apply to be lead plaintiffs by April 6, 2026, to share in any potential recovery, with the assurance that participation does not require serving as lead plaintiff.
- Law Firm's Advantage: Bronstein, Gewirtz & Grossman LLC operates on a contingency fee basis, having successfully recovered hundreds of millions for investors nationwide, emphasizing their expertise in securities fraud class actions and the importance of maintaining market integrity.
See More
Faruqi & Faruqi Investigates Mereo BioPharma for Securities Violations
- Legal Investigation Launched: Faruq & Faruqi LLP is investigating potential securities claims against Mereo BioPharma, specifically urging investors who purchased securities between June 5, 2023, and December 26, 2025, to contact them before the April 6, 2026, deadline to seek lead plaintiff status.
- Lawsuit Allegations Overview: The lawsuit alleges that Mereo and its executives violated federal securities laws by failing to disclose the true status of the Phase 3 ORBIT and COSMIC programs, both of which failed to meet their primary endpoints for reducing clinical fracture rates, resulting in significant investor losses.
- Stock Price Plunge Impact: Following Mereo's announcement on December 29, 2025, that both Phase 3 studies failed to meet primary endpoints, the stock price plummeted by $2.02, or 87.64%, closing at $0.28 per share, reflecting extreme market pessimism regarding the company's outlook.
- Investor Rights Protection: Faruq & Faruqi encourages anyone with information regarding Mereo BioPharma's conduct, including whistleblowers and former employees, to contact the firm to provide legal support for affected investors, ensuring their rights are protected.
See More
Reminder of Class Action for Mereo BioPharma ADS Purchasers
- Class Action Notice: Rosen Law Firm reminds investors who purchased Mereo BioPharma ADS between June 5, 2023, and December 26, 2025, to apply as lead plaintiffs by April 6, 2026, to participate in the class action and seek compensation.
- Lawsuit Background: The lawsuit alleges that defendants provided false and misleading information regarding the Phase 3 Orbit and COSMIC studies, leading investors to purchase Mereo's ADS at artificially inflated prices, resulting in financial losses when the truth emerged.
- Law Firm's Advantage: Rosen Law Firm specializes in securities class actions and has recovered over $438 million for investors in 2019 alone, demonstrating its successful track record and extensive experience in this field.
- Investor Selection Advice: Investors are advised to carefully choose law firms with proven success in securities litigation to ensure effective legal support in class actions, avoiding firms that merely act as intermediaries.
See More
Mereo BioPharma Class Action Notice Issued
- Class Action Initiation: Rosen Law Firm reminds investors who purchased Mereo BioPharma ADS between June 5, 2023, and December 26, 2025, to apply as lead plaintiffs by April 6, 2026, to participate in the class action and potentially receive compensation without any out-of-pocket costs.
- Lawsuit Background: The lawsuit alleges that defendants provided false and misleading information regarding the expected results of the Phase 3 Orbit and COSMIC studies for setrusumab, leading investors to purchase Mereo's ADS at artificially inflated prices, resulting in financial losses when the truth emerged.
- Law Firm's Credentials: Rosen Law Firm specializes in securities class actions and has recovered over $438 million for investors in 2019 alone, being ranked first in 2017 for the number of securities class action settlements, showcasing its expertise in this field.
- Investor Advisory: Investors are advised to carefully select legal counsel, with Rosen Law Firm recommending choosing qualified attorneys with a proven track record in leadership roles to ensure optimal representation in the class action.
See More
Class Action Lawsuit Filed Against Mereo BioPharma Group plc
- Class Action Initiated: Pomerantz LLP has filed a class action lawsuit against Mereo BioPharma, alleging securities fraud and other unlawful business practices by the company and certain executives, with investors advised to apply as Lead Plaintiff by April 6, 2026, indicating significant investor dissatisfaction with corporate governance.
- Stock Price Plummets: On December 29, 2025, Mereo announced that neither the Orbit nor Cosmic Phase 3 studies achieved statistical significance, resulting in an 87.7% drop in its American Depositary Receipt (ADR) price to $0.29, reflecting extreme market pessimism regarding the company's future prospects.
- Clinical Trial Failures: Although Mereo indicated on July 9, 2025, that its UX143 study for osteogenesis imperfecta was progressing, the final results failed to meet primary endpoints, highlighting significant challenges in its R&D efforts that could impact future financing and partnership opportunities.
- Severe Legal Consequences: The lawsuit could lead to substantial financial liabilities for Mereo, potentially damaging its reputation and investor confidence, further exacerbating market skepticism about its business model.
See More
Class Action Filed Against Mereo BioPharma Group plc for Securities Violations
- Lawsuit Background: Bronstein, Gewirtz & Grossman LLC has filed a class action lawsuit against Mereo BioPharma Group plc, alleging violations of federal securities laws from June 5, 2023, to December 26, 2025, seeking to recover damages for investors.
- False Statements Allegation: The complaint claims that during the class period, defendants made overly positive statements to investors while concealing significant adverse facts regarding the Phase 3 ORBIT and COSMIC programs, misleading investors about the company's true condition.
- Investor Action: Affected investors are encouraged to apply to be lead plaintiffs by April 6, 2026, to share in any potential recovery, with the option to participate without needing to serve as lead plaintiff.
- Law Firm Background: Bronstein, Gewirtz & Grossman LLC is a nationally recognized firm specializing in securities fraud class actions, having recovered hundreds of millions for investors nationwide, highlighting its critical role in upholding market integrity.
See More
Class Action Filed Against Mereo BioPharma Group plc
- Lawsuit Background: Bronstein, Gewirtz & Grossman LLC has filed a class action lawsuit against Mereo BioPharma Group plc, alleging violations of federal securities laws on behalf of all investors who purchased Mereo securities between June 5, 2023, and December 26, 2025.
- False Statements Allegation: The complaint claims that throughout the class period, defendants made overwhelmingly positive statements while disseminating materially false and misleading information, concealing adverse facts about the Phase 3 ORBIT and COSMIC programs, both of which failed to meet their primary endpoints for reducing clinical fracture rates.
- Investor Action: Affected investors are encouraged to apply to be lead plaintiffs by April 6, 2026, to share in any potential recovery, with the assurance that participation does not require serving as lead plaintiff.
- Law Firm's Advantage: Bronstein, Gewirtz & Grossman LLC operates on a contingency fee basis, having successfully recovered hundreds of millions for investors nationwide, emphasizing their expertise in securities fraud class actions and the importance of maintaining market integrity.
See More
Faruqi & Faruqi Investigates Mereo BioPharma for Securities Violations
- Legal Investigation Launched: Faruq & Faruqi LLP is investigating potential securities claims against Mereo BioPharma, specifically urging investors who purchased securities between June 5, 2023, and December 26, 2025, to contact them before the April 6, 2026, deadline to seek lead plaintiff status.
- Lawsuit Allegations Overview: The lawsuit alleges that Mereo and its executives violated federal securities laws by failing to disclose the true status of the Phase 3 ORBIT and COSMIC programs, both of which failed to meet their primary endpoints for reducing clinical fracture rates, resulting in significant investor losses.
- Stock Price Plunge Impact: Following Mereo's announcement on December 29, 2025, that both Phase 3 studies failed to meet primary endpoints, the stock price plummeted by $2.02, or 87.64%, closing at $0.28 per share, reflecting extreme market pessimism regarding the company's outlook.
- Investor Rights Protection: Faruq & Faruqi encourages anyone with information regarding Mereo BioPharma's conduct, including whistleblowers and former employees, to contact the firm to provide legal support for affected investors, ensuring their rights are protected.
See More
Reminder of Class Action for Mereo BioPharma ADS Purchasers
- Class Action Notice: Rosen Law Firm reminds investors who purchased Mereo BioPharma ADS between June 5, 2023, and December 26, 2025, to apply as lead plaintiffs by April 6, 2026, to participate in the class action and seek compensation.
- Lawsuit Background: The lawsuit alleges that defendants provided false and misleading information regarding the Phase 3 Orbit and COSMIC studies, leading investors to purchase Mereo's ADS at artificially inflated prices, resulting in financial losses when the truth emerged.
- Law Firm's Advantage: Rosen Law Firm specializes in securities class actions and has recovered over $438 million for investors in 2019 alone, demonstrating its successful track record and extensive experience in this field.
- Investor Selection Advice: Investors are advised to carefully choose law firms with proven success in securities litigation to ensure effective legal support in class actions, avoiding firms that merely act as intermediaries.
See More
Mereo BioPharma Class Action Notice Issued
- Class Action Initiation: Rosen Law Firm reminds investors who purchased Mereo BioPharma ADS between June 5, 2023, and December 26, 2025, to apply as lead plaintiffs by April 6, 2026, to participate in the class action and potentially receive compensation without any out-of-pocket costs.
- Lawsuit Background: The lawsuit alleges that defendants provided false and misleading information regarding the expected results of the Phase 3 Orbit and COSMIC studies for setrusumab, leading investors to purchase Mereo's ADS at artificially inflated prices, resulting in financial losses when the truth emerged.
- Law Firm's Credentials: Rosen Law Firm specializes in securities class actions and has recovered over $438 million for investors in 2019 alone, being ranked first in 2017 for the number of securities class action settlements, showcasing its expertise in this field.
- Investor Advisory: Investors are advised to carefully select legal counsel, with Rosen Law Firm recommending choosing qualified attorneys with a proven track record in leadership roles to ensure optimal representation in the class action.
See More
Class Action Lawsuit Filed Against Mereo BioPharma Group plc
- Class Action Initiated: Pomerantz LLP has filed a class action lawsuit against Mereo BioPharma, alleging securities fraud and other unlawful business practices by the company and certain executives, with investors advised to apply as Lead Plaintiff by April 6, 2026, indicating significant investor dissatisfaction with corporate governance.
- Stock Price Plummets: On December 29, 2025, Mereo announced that neither the Orbit nor Cosmic Phase 3 studies achieved statistical significance, resulting in an 87.7% drop in its American Depositary Receipt (ADR) price to $0.29, reflecting extreme market pessimism regarding the company's future prospects.
- Clinical Trial Failures: Although Mereo indicated on July 9, 2025, that its UX143 study for osteogenesis imperfecta was progressing, the final results failed to meet primary endpoints, highlighting significant challenges in its R&D efforts that could impact future financing and partnership opportunities.
- Severe Legal Consequences: The lawsuit could lead to substantial financial liabilities for Mereo, potentially damaging its reputation and investor confidence, further exacerbating market skepticism about its business model.
See More
Class Action Filed Against Mereo BioPharma Group plc for Securities Violations
- Lawsuit Background: Bronstein, Gewirtz & Grossman LLC has filed a class action lawsuit against Mereo BioPharma Group plc, alleging violations of federal securities laws from June 5, 2023, to December 26, 2025, seeking to recover damages for investors.
- False Statements Allegation: The complaint claims that during the class period, defendants made overly positive statements to investors while concealing significant adverse facts regarding the Phase 3 ORBIT and COSMIC programs, misleading investors about the company's true condition.
- Investor Action: Affected investors are encouraged to apply to be lead plaintiffs by April 6, 2026, to share in any potential recovery, with the option to participate without needing to serve as lead plaintiff.
- Law Firm Background: Bronstein, Gewirtz & Grossman LLC is a nationally recognized firm specializing in securities fraud class actions, having recovered hundreds of millions for investors nationwide, highlighting its critical role in upholding market integrity.
See More
