Gossamer Bio's Phase 3 Trial Results Disappoint
Written by Emily J. Thompson, Senior Investment Analyst
Updated: Feb 23 2026
0mins
Source: Benzinga
Gossamer Bio's shares fell sharply, hitting a 52-week low, following disappointing results from its Phase 3 PROSERA trial for seralutinib, which showed significant but insufficient improvement in patient mobility.
The trial revealed that seralutinib led to a median change of +28.2 meters in Six-Minute Walk Distance (6MWD) at Week 24, failing to meet the predefined efficacy threshold. However, in a subgroup of patients with connective tissue disease-associated pulmonary arterial hypertension, the drug achieved a placebo-adjusted gain of +37.0 meters, indicating potential effectiveness. Gossamer plans to meet with the U.S. FDA to discuss future development for seralutinib while pausing enrollment in the SERANATA study to evaluate the impact of these results.
The market reacted negatively, with Gossamer Bio's shares plummeting by 77.12% to $0.59, reflecting investor disappointment and prompting analysts to lower their earnings expectations.
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Analyst Views on GOSS
Wall Street analysts forecast GOSS stock price to rise
4 Analyst Rating
3 Buy
1 Hold
0 Sell
Strong Buy
Current: 0.156
Low
10.00
Averages
12.33
High
15.00
Current: 0.156
Low
10.00
Averages
12.33
High
15.00
About GOSS
Gossamer Bio, Inc. is a late-stage, clinical biopharmaceutical company, which is focused on the development and commercialization of seralutinib for the treatment of pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease (PH-ILD). Seralutinib, also known as GB002, is an investigational inhaled, small-molecule, platelet-derived growth factor receptor (PDGFR), colony-stimulating factor 1 receptor (CSF1R), and c-KIT inhibitor, being evaluated in a Phase III clinical trial for the treatment of PAH. Seralutinib is designed to target the mechanisms that underlie pulmonary hypertension and to be delivered to the site of disease, via dry powder inhaler. Seralutinib is being evaluated in a Phase III clinical trial for the treatment of pulmonary arterial hypertension (PAH). Inhaled seralutinib, which is designed to act on both isoforms of the PDGFR, α and β, as well as the CSF1R and c-KIT pathways.
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.
Harbour BioMed Appoints Dr. Luisa Salter-Cid as Scientific Advisor
- New Scientific Advisor: Harbour BioMed has appointed Dr. Luisa Salter-Cid as Scientific Advisor, bringing over 20 years of leadership experience in biotech and pharmaceuticals, which is expected to enrich the company's expertise and strategic direction.
- Clinical Development Achievements: During her tenure at Bristol Myers Squibb, Salter-Cid successfully advanced over 20 compounds into clinical development, showcasing her exceptional ability to translate discoveries into clinical applications, which will help accelerate Harbour BioMed's antibody therapeutic pipeline.
- Technological Platform Advantage: Harbour BioMed's Harbour Mice® technology platform generates fully human monoclonal antibodies, and combined with HCAb technology, it offers tumor-killing effects that traditional combination therapies cannot achieve, with Salter-Cid's expertise likely enhancing its application potential.
- Global Medical Needs: Salter-Cid's strategic insights will assist Harbour BioMed in addressing unmet medical needs globally, driving the company's efforts in innovative drug development, thereby enhancing its market competitiveness and industry standing.
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- Class Action Initiated: Bronstein, Gewirtz & Grossman, LLC has announced a class action lawsuit against Gossamer Bio, seeking damages for investors who purchased securities between June 16, 2025, and February 20, 2026, indicating significant legal risks that could impact the company's stock performance.
- Allegations of False Statements: The complaint alleges that Gossamer Bio concealed critical adverse facts regarding inadequate placebo control at Latin American testing sites while promoting positive results from its Phase 3 PROSERA study, leading investors to purchase shares at artificially inflated prices, potentially triggering a market trust crisis.
- Investor Rights Protection: Investors are encouraged to apply to be lead plaintiffs by June 1, 2026, indicating that the legal process provides an opportunity for affected investors to recover losses, which may influence the company's future capital structure and investor confidence.
- Law Firm Background: Bronstein, Gewirtz & Grossman, LLC is a nationally recognized firm that has recovered hundreds of millions for investors, showcasing its expertise in securities fraud cases, which may attract more investors to participate in the lawsuit.
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- Gossamer Bio Lawsuit: Gossamer Bio (NASDAQ:GOSS) faces a class action for failing to disclose that Latin American patients performed well on placebo, leading to the Phase 3 PROSERA study not meeting its primary endpoint, with shareholders encouraged to participate before the deadline.
- New Era Energy Issues: New Era Energy & Digital (NASDAQ:NUAI) is accused of overstating progress on its Texas Critical Data Centers project and engaging in fraudulent schemes, prompting shareholders to act before the deadline.
- Medpace Holdings Allegations: Medpace Holdings (NASDAQ:MEDP) is under scrutiny for misleading statements regarding its projected book-to-bill ratio for Q4 2025, with investors advised to participate in the lawsuit before the deadline.
- Legal Consultation Advice: The Law Offices of Frank R. Cruz remind investors who suffered losses during the relevant periods to contact them to understand their legal rights and steps to participate in the class actions.
See More
Gossamer Bio Faces Securities Class Action Lawsuit
- Lawsuit Background: Gossamer Bio, Inc. is facing a securities class action lawsuit following its February 23, 2026 announcement that the PROSERA study failed to meet its primary endpoint, involving investors who purchased securities between June 16, 2025, and February 20, 2026, indicating potential missteps in clinical trial design.
- Stock Price Plunge: Following the lawsuit announcement, Gossamer's stock price plummeted by 80%, reflecting a severe loss of investor confidence in the company's future prospects, which may jeopardize its listing status on Nasdaq.
- Investor Losses: Hagens Berman law firm is urging investors who suffered substantial losses during the class period to submit claims, suggesting that this event could trigger a wave of investor claims, further impacting the company's financial health.
- Regulatory Scrutiny: The lawsuit alleges improper disclosures regarding trial design and patient recruitment, which may subject Gossamer to stricter regulatory scrutiny, affecting its future financing and market credibility.
See More
Gossamer Bio Faces Class Action Lawsuit Reminder
- Class Action Reminder: The Schall Law Firm reminds investors of a class action lawsuit against Gossamer Bio for violations of §§10(b) and 20(a) of the Securities Exchange Act, concerning securities purchased between June 16, 2025, and February 20, 2026, with a deadline to contact the firm by June 1, 2026.
- False Statements Allegation: The complaint alleges that Gossamer concealed adverse facts regarding the design of its Phase 3 PROSERA study, particularly concerning controls for placebo response at certain testing sites, rendering its public statements false and materially misleading throughout the class period.
- Investor Losses: As the market learned the truth about Gossamer, investors suffered damages, indicating significant deficiencies in the company's disclosure practices that could adversely affect its future stock performance and investor confidence.
- Legal Consultation Opportunity: The Schall Law Firm offers free consultations and encourages affected investors to take action before the class action is certified to ensure their rights are protected and to avoid being an absent class member.
See More
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- Lawsuit Background: Gossamer Bio, Inc. is facing a class action lawsuit following its February 23, 2026 announcement that the PROSERA study failed to meet its primary endpoint, involving investors who purchased securities between June 16, 2025, and February 20, 2026, indicating potential missteps in clinical trial design.
- Stock Price Plunge: Following the trial failure announcement, Gossamer's stock plummeted by 80%, reflecting investor disappointment in the company's future prospects and prompting Hagens Berman to investigate possible violations of federal securities laws, which could lead to further legal liabilities.
- Trial Design Issues: The lawsuit alleges that Gossamer misrepresented the PROSERA trial design, including patient recruitment and monitoring, as management previously claimed the drug had the potential to be a “first-in-class therapeutic,” but the actual results failed to support this assertion, potentially undermining investor confidence.
- Nasdaq Compliance Risks: On April 9, 2026, Gossamer revealed that it had not met the minimum bid price requirement ($1) for continued listing on the Nasdaq Global Select Market since February 24, 2026, exacerbating investor concerns about the company's future and potentially impacting its ability to raise capital and maintain market position.
See More
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- New Scientific Advisor: Harbour BioMed has appointed Dr. Luisa Salter-Cid as Scientific Advisor, bringing over 20 years of leadership experience in biotech and pharmaceuticals, which is expected to enrich the company's expertise and strategic direction.
- Clinical Development Achievements: During her tenure at Bristol Myers Squibb, Salter-Cid successfully advanced over 20 compounds into clinical development, showcasing her exceptional ability to translate discoveries into clinical applications, which will help accelerate Harbour BioMed's antibody therapeutic pipeline.
- Technological Platform Advantage: Harbour BioMed's Harbour Mice® technology platform generates fully human monoclonal antibodies, and combined with HCAb technology, it offers tumor-killing effects that traditional combination therapies cannot achieve, with Salter-Cid's expertise likely enhancing its application potential.
- Global Medical Needs: Salter-Cid's strategic insights will assist Harbour BioMed in addressing unmet medical needs globally, driving the company's efforts in innovative drug development, thereby enhancing its market competitiveness and industry standing.
See More
Class Action Filed Against Gossamer Bio for Securities Violations
- Class Action Initiated: Bronstein, Gewirtz & Grossman, LLC has announced a class action lawsuit against Gossamer Bio, seeking damages for investors who purchased securities between June 16, 2025, and February 20, 2026, indicating significant legal risks that could impact the company's stock performance.
- Allegations of False Statements: The complaint alleges that Gossamer Bio concealed critical adverse facts regarding inadequate placebo control at Latin American testing sites while promoting positive results from its Phase 3 PROSERA study, leading investors to purchase shares at artificially inflated prices, potentially triggering a market trust crisis.
- Investor Rights Protection: Investors are encouraged to apply to be lead plaintiffs by June 1, 2026, indicating that the legal process provides an opportunity for affected investors to recover losses, which may influence the company's future capital structure and investor confidence.
- Law Firm Background: Bronstein, Gewirtz & Grossman, LLC is a nationally recognized firm that has recovered hundreds of millions for investors, showcasing its expertise in securities fraud cases, which may attract more investors to participate in the lawsuit.
See More
Class Action Lawsuits Reminder for Shareholders
- Gossamer Bio Lawsuit: Gossamer Bio (NASDAQ:GOSS) faces a class action for failing to disclose that Latin American patients performed well on placebo, leading to the Phase 3 PROSERA study not meeting its primary endpoint, with shareholders encouraged to participate before the deadline.
- New Era Energy Issues: New Era Energy & Digital (NASDAQ:NUAI) is accused of overstating progress on its Texas Critical Data Centers project and engaging in fraudulent schemes, prompting shareholders to act before the deadline.
- Medpace Holdings Allegations: Medpace Holdings (NASDAQ:MEDP) is under scrutiny for misleading statements regarding its projected book-to-bill ratio for Q4 2025, with investors advised to participate in the lawsuit before the deadline.
- Legal Consultation Advice: The Law Offices of Frank R. Cruz remind investors who suffered losses during the relevant periods to contact them to understand their legal rights and steps to participate in the class actions.
See More
Gossamer Bio Faces Securities Class Action Lawsuit
- Lawsuit Background: Gossamer Bio, Inc. is facing a securities class action lawsuit following its February 23, 2026 announcement that the PROSERA study failed to meet its primary endpoint, involving investors who purchased securities between June 16, 2025, and February 20, 2026, indicating potential missteps in clinical trial design.
- Stock Price Plunge: Following the lawsuit announcement, Gossamer's stock price plummeted by 80%, reflecting a severe loss of investor confidence in the company's future prospects, which may jeopardize its listing status on Nasdaq.
- Investor Losses: Hagens Berman law firm is urging investors who suffered substantial losses during the class period to submit claims, suggesting that this event could trigger a wave of investor claims, further impacting the company's financial health.
- Regulatory Scrutiny: The lawsuit alleges improper disclosures regarding trial design and patient recruitment, which may subject Gossamer to stricter regulatory scrutiny, affecting its future financing and market credibility.
See More
Gossamer Bio Faces Class Action Lawsuit Reminder
- Class Action Reminder: The Schall Law Firm reminds investors of a class action lawsuit against Gossamer Bio for violations of §§10(b) and 20(a) of the Securities Exchange Act, concerning securities purchased between June 16, 2025, and February 20, 2026, with a deadline to contact the firm by June 1, 2026.
- False Statements Allegation: The complaint alleges that Gossamer concealed adverse facts regarding the design of its Phase 3 PROSERA study, particularly concerning controls for placebo response at certain testing sites, rendering its public statements false and materially misleading throughout the class period.
- Investor Losses: As the market learned the truth about Gossamer, investors suffered damages, indicating significant deficiencies in the company's disclosure practices that could adversely affect its future stock performance and investor confidence.
- Legal Consultation Opportunity: The Schall Law Firm offers free consultations and encourages affected investors to take action before the class action is certified to ensure their rights are protected and to avoid being an absent class member.
See More
Gossamer Bio Faces Class Action Lawsuit Over Trial Failures
- Lawsuit Background: Gossamer Bio, Inc. is facing a class action lawsuit following its February 23, 2026 announcement that the PROSERA study failed to meet its primary endpoint, involving investors who purchased securities between June 16, 2025, and February 20, 2026, indicating potential missteps in clinical trial design.
- Stock Price Plunge: Following the trial failure announcement, Gossamer's stock plummeted by 80%, reflecting investor disappointment in the company's future prospects and prompting Hagens Berman to investigate possible violations of federal securities laws, which could lead to further legal liabilities.
- Trial Design Issues: The lawsuit alleges that Gossamer misrepresented the PROSERA trial design, including patient recruitment and monitoring, as management previously claimed the drug had the potential to be a “first-in-class therapeutic,” but the actual results failed to support this assertion, potentially undermining investor confidence.
- Nasdaq Compliance Risks: On April 9, 2026, Gossamer revealed that it had not met the minimum bid price requirement ($1) for continued listing on the Nasdaq Global Select Market since February 24, 2026, exacerbating investor concerns about the company's future and potentially impacting its ability to raise capital and maintain market position.
See More
