- Study demonstrates superiority, showing both statistically significant and clinically meaningful reduction in annualized bleeding rate with a generally well-tolerated safety profile compared to on-demand treatment in patients 12 years and older
- HYMPAVZI was administered with a straightforward, once-weekly subcutaneous injection that required minimal preparation
NEW YORK, NY, USA I June 26, 2025 I Pfizer Inc. (NYSE: PFE)today announced positive topline results from the Phase 3 BASIS study (NCT03938792) evaluating HYMPAVZI™ (marstacimab) for adults and adolescents living with hemophilia A or B with inhibitors. The study met the primary endpoint and key secondary bleeding endpoints demonstrating the superiority of once-weekly subcutaneous HYMPAVZI in improving key bleeding outcomes compared to on-demand treatment in a patient population where less burdensome treatment approaches are needed.1,2,3,4
Inhibitors, or antibodies, which neutralize factor replacement therapies and render them ineffective, may develop in people living with hemophilia.5 Inhibitors can be diagnosed with a blood test.6 Of the more than 800,000 people in the world living with hemophilia A or hemophilia B, approximately 20% of people with hemophilia A and 3% of people with hemophilia B are unable to continue taking factor replacement therapies because they develop inhibitors to FVIII (Factor VIII) and FIX (Factor IX) and these therapies no longer prevent or stop bleeding episodes.6,7
“Patients with inhibitors tend to face frequent complications, and navigating the treatment landscape can introduce complexities and increase disease burden,”1,2,3,4,8 said Davide Matino, M.D., M.Sc., BASIS Principal Investigator, Associate Professor of Medicine, McMaster University. “The strong bleed reduction with HYMPAVZI compared to on-demand treatment in the Phase 3 BASIS study, coupled with its weekly administration method, offers exciting potential for these patients who are in critical need of treatment options.”
The BASIS trial demonstrated that prophylactic treatment with HYMPAVZI resulted in a statistically significant and clinically relevant reduction in annualized bleeding rate (ABR) of treated bleeds in people living with severe hemophilia A or hemophilia B with inhibitors. Forty-eight people living with hemophilia were treated with HYMPAVZI during a 12-month period versus an on-demand intravenous regimen with bypassing agents, administered as part of usual care in the six-month lead-in period. HYMPAVZI was superior to on-demand treatment with a 93% reduction in ABR over 12 months (ABR 1.39 vs ABR on-demand 19.78; p < 0.0001). Superiority of HYMPAVZI was also demonstrated across all bleeding-related secondary endpoints—spontaneous bleeds, joint bleeds, target joint bleeds, and total bleeds.
HYMPAVZI was generally well-tolerated, consistent with the non-inhibitor cohort of the BASIS study and Phase 1/2 results. No deaths or thromboembolic events were reported.
“These encouraging results demonstrate HYMPAVZI’s potential to help people living with hemophilia A or B with inhibitors, meeting an important need for patients with antibodies that neutralize most factor-based prophylactic options used to manage bleeding episodes,” said Michael Vincent, M.D., Ph.D., Chief Inflammation & Immunology Officer, Pfizer. “HYMPAVZI represents Pfizer’s latest contribution in more than 40 years of working to advance hemophilia care, as a generally well-tolerated treatment option that could offer bleed protection with a straightforward, once-weekly subcutaneous administration in a pre-filled pen for patients with inhibitors, if approved in this patient population.”
Analyses of the full Phase 3 dataset from the inhibitor cohort of the BASIS study are ongoing, and additional data will be presented at upcoming medical meetings. Pfizer plans to discuss these data with regulatory authorities, with the goal of initiating regulatory filings for HYMPAVZI for the treatment of patients living with hemophilia with inhibitors.
Discovered by Pfizer scientists, HYMPAVZI has a mechanism of action that is differentiated from FVIII and FIX replacement treatments. Instead of replacing missing or insufficient clotting factors, HYMPAVZI is intentionally designed to target tissue factor pathway inhibitor (TFPI), one of the body’s natural mechanisms that inhibits the initiation of blood clotting. By targeting the Kunitz 2 domain of TFPI, HYMPAVZI may help re-establish balance between bleeding and blood clot formation with the goal of offering a combination of bleed protection, good tolerability, and straightforward administration.
About the BASIS study
The pivotal BASIS study is a global Phase 3, open-label, multicenter study to evaluate the efficacy and safety of HYMPAVZI in adolescent and adult participants ages 12 to <75 years with severe hemophilia A (defined as FVIII <1%) or moderately severe to severe hemophilia B (defined as FIX activity ≤2%) with or without inhibitors.
This cohort included 48 people living with hemophilia with inhibitors who were treated with HYMPAVZI during a 12-month active treatment period (ATP) versus an on-demand intravenous regimen with bypassing agents, administered as part of usual care in a six-month observational period. During the ATP, participants received prophylaxis (a 300 mg subcutaneous loading dose of HYMPAVZI, followed by 150 mg subcutaneously once weekly) with potential for dose escalation to 300 mg once weekly. An additional three patients in the inhibitor cohort were on routine prophylactic treatment prior to the study and not included in the primary efficacy analysis.
The primary endpoint measures the treated ABR during the 12-month ATP with HYMPAVZI compared to treated ABR on prior on-demand replacement therapy. For further information, visit clinicaltrials.gov.
About HYMPAVZI
HYMPAVZI has received regulatory approvals in the U.S. and in Europe for eligible patients living with hemophilia A without factor VIII inhibitors, or hemophilia B without factor IX inhibitors. HYMPAVZI was the first anti-TFPI approved in the U.S. and EU for the treatment of hemophilia A or B and the first hemophilia medicine approved in the U.S. and EU to be administered via a pre-filled, auto-injector pen. For eligible people living with hemophilia B, it is the first once-weekly subcutaneous prophylactic treatment. HYMPAVZI can offer a subcutaneous treatment option with a once-weekly dosing schedule and minimal preparation required for each individual administration.
Pfizer is also conducting BASIS KIDS, an open-label study investigating the safety and efficacy of HYMPAVZI in children 1 to <18 years of age with severe hemophilia A or moderately severe to severe hemophilia B with or without inhibitors.
About Hemophilia
Hemophilia is a family of rare genetic blood diseases caused by a clotting factor deficiency (FVIII in hemophilia A, FIX in hemophilia B), which prevents normal blood clotting. Hemophilia is diagnosed in early childhood and impacts more than 800,000 people worldwide.7 The inability of the blood to clot properly can increase the risk of painful bleeding inside the joints, which can cause joint scarring and damage. People living with hemophilia can suffer permanent joint damage following repeated bleeding episodes.9,10
For decades, the most common treatment approach for hemophilia A and B has been factor replacement therapy, which replaces the missing clotting factors. Factor replacement therapies increase the amount of clotting factor in the body to levels that improve clotting, resulting in less bleeding. The burden of intravenous infusions is believed to be a barrier to treatment adherence for some people living with hemophilia due in part to inconvenience, time constraints, and poor venous access.11
Approximately 20% of people with hemophilia A and 3% of people with hemophilia B are unable to continue taking factor replacement therapies because they develop inhibitors to FVIII and FIX.6 These patients often have higher treatment burden, including potential complications from bleeding such as hospitalization and death, as well as higher treatment-related costs.1,2,3,4,12
The full Prescribing Information can be found here.
About Pfizer: Breakthroughs That Change Patients’ Lives
At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world’s premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at www.Pfizer.com. In addition, to learn more, please visit us on www.Pfizer.com and follow us on X at @Pfizer and @Pfizer_News, LinkedIn, YouTube and like us on Facebook at www.facebook.com/Pfizer/.
1 Shapiro AD, Ragni MV, Borhany M, et al. Natural history study of factor IX deficiency with focus on treatment and complications (B-Natural). Haemophilia. 2021;27(1):49-59. doi: 10.1111/hae.14139.
2 Valentino LA, Ewenstein B, Navickis RJ, Wilkes MM. Central venous access devices in haemophilia. Haemophilia. 2004;10(2):134-46. doi: 10.1046/j.1365-2516.2003.00840.x.
3 Nugent D, Kalnins W, Querol F, et al. Haemophilia Experiences, Results and Opportunities (HERO) study: Treatment-related characteristics of the population. Haemophilia. 2015;21(1):e26-38. doi: 10.1111/hae.12545.
4 Soucie JM, Symons Jt, Evatt B, Brettler D, Huszti H, Linden J. Home-based factor infusion therapy and hospitalization for bleeding complications among males with haemophilia. Haemophilia. 2001;7(2):198-206. doi: 10.1046/j.1365-2516.2001.00484.x.
5 Teiu P, Chan A, Matino D. Molecular Mechanisms of Inhibitor Development in Hemophilia. Mediterr J Hematol Infect Dis. 2020 Jan 1;12(1):e2020001. doi: 10.4084/MJHID.2020.001.
6 Centers of Disease Control and Prevention. Testing for Inhibitors and Hemophilia. Accessed May 14, 2025. Available at: https://www.cdc.gov/hemophilia/testing/testing-for-inhibitors-and-hemophilia.html?CDC_AAref_Val=https://www.cdc.gov/ncbddd/hemophilia/inhibitors.html.
7 World Federation of Hemophilia. World Federation of Hemophilia Global Report on the Annual Global Survey 2022. https://www1.wfh.org/publications/files/pdf-2399.pdf.
8 Meeks S, Batsuli G. Hemophilia and inhibitors: Current treatment options and potential new therapeutic approaches. Hematology Am Soc Hematol Educ Program. 2016 Dec 2;2016(1):657–662. doi:10.1182/asheducation-2016.1.657.
9 Srivastava A, Santagostino E, Dougall A, et al. WFH guidelines for the management of hemophilia, 3rd Edition; 2020. Haemophilia. 26(S6), 1–158. https://doi.org/10.1111/hae.14046.
10 Franchini M, Mannucci PM. Past, present and future of hemophilia: A narrative review. Orphanet J Rare Dis. 2012;7:24. https://doi.org/10.1186/1750-1172-7-24.
11 Weyand AC, Pipe SW. New therapies for hemophilia. Blood. 2019;133(5):389–398. https://doi.org/10.1182/blood-2018-08-872291.
12 Walsh CE, Soucie JM, Miller CH. Impact of inhibitors on hemophilia a mortality in the United States. Am. J. Hematol. 2015; 90: 400-405. https://doi.org/10.1002/ajh.23957.
SOURCE: Pfizer
Post Views: 2,168
- Study demonstrates superiority, showing both statistically significant and clinically meaningful reduction in annualized bleeding rate with a generally well-tolerated safety profile compared to on-demand treatment in patients 12 years and older
- HYMPAVZI was administered with a straightforward, once-weekly subcutaneous injection that required minimal preparation
NEW YORK, NY, USA I June 26, 2025 I Pfizer Inc. (NYSE: PFE)today announced positive topline results from the Phase 3 BASIS study (NCT03938792) evaluating HYMPAVZI™ (marstacimab) for adults and adolescents living with hemophilia A or B with inhibitors. The study met the primary endpoint and key secondary bleeding endpoints demonstrating the superiority of once-weekly subcutaneous HYMPAVZI in improving key bleeding outcomes compared to on-demand treatment in a patient population where less burdensome treatment approaches are needed.1,2,3,4
Inhibitors, or antibodies, which neutralize factor replacement therapies and render them ineffective, may develop in people living with hemophilia.5 Inhibitors can be diagnosed with a blood test.6 Of the more than 800,000 people in the world living with hemophilia A or hemophilia B, approximately 20% of people with hemophilia A and 3% of people with hemophilia B are unable to continue taking factor replacement therapies because they develop inhibitors to FVIII (Factor VIII) and FIX (Factor IX) and these therapies no longer prevent or stop bleeding episodes.6,7
“Patients with inhibitors tend to face frequent complications, and navigating the treatment landscape can introduce complexities and increase disease burden,”1,2,3,4,8 said Davide Matino, M.D., M.Sc., BASIS Principal Investigator, Associate Professor of Medicine, McMaster University. “The strong bleed reduction with HYMPAVZI compared to on-demand treatment in the Phase 3 BASIS study, coupled with its weekly administration method, offers exciting potential for these patients who are in critical need of treatment options.”
The BASIS trial demonstrated that prophylactic treatment with HYMPAVZI resulted in a statistically significant and clinically relevant reduction in annualized bleeding rate (ABR) of treated bleeds in people living with severe hemophilia A or hemophilia B with inhibitors. Forty-eight people living with hemophilia were treated with HYMPAVZI during a 12-month period versus an on-demand intravenous regimen with bypassing agents, administered as part of usual care in the six-month lead-in period. HYMPAVZI was superior to on-demand treatment with a 93% reduction in ABR over 12 months (ABR 1.39 vs ABR on-demand 19.78; p < 0.0001). Superiority of HYMPAVZI was also demonstrated across all bleeding-related secondary endpoints—spontaneous bleeds, joint bleeds, target joint bleeds, and total bleeds.
HYMPAVZI was generally well-tolerated, consistent with the non-inhibitor cohort of the BASIS study and Phase 1/2 results. No deaths or thromboembolic events were reported.
“These encouraging results demonstrate HYMPAVZI’s potential to help people living with hemophilia A or B with inhibitors, meeting an important need for patients with antibodies that neutralize most factor-based prophylactic options used to manage bleeding episodes,” said Michael Vincent, M.D., Ph.D., Chief Inflammation & Immunology Officer, Pfizer. “HYMPAVZI represents Pfizer’s latest contribution in more than 40 years of working to advance hemophilia care, as a generally well-tolerated treatment option that could offer bleed protection with a straightforward, once-weekly subcutaneous administration in a pre-filled pen for patients with inhibitors, if approved in this patient population.”
Analyses of the full Phase 3 dataset from the inhibitor cohort of the BASIS study are ongoing, and additional data will be presented at upcoming medical meetings. Pfizer plans to discuss these data with regulatory authorities, with the goal of initiating regulatory filings for HYMPAVZI for the treatment of patients living with hemophilia with inhibitors.
Discovered by Pfizer scientists, HYMPAVZI has a mechanism of action that is differentiated from FVIII and FIX replacement treatments. Instead of replacing missing or insufficient clotting factors, HYMPAVZI is intentionally designed to target tissue factor pathway inhibitor (TFPI), one of the body’s natural mechanisms that inhibits the initiation of blood clotting. By targeting the Kunitz 2 domain of TFPI, HYMPAVZI may help re-establish balance between bleeding and blood clot formation with the goal of offering a combination of bleed protection, good tolerability, and straightforward administration.
About the BASIS study
The pivotal BASIS study is a global Phase 3, open-label, multicenter study to evaluate the efficacy and safety of HYMPAVZI in adolescent and adult participants ages 12 to <75 years with severe hemophilia A (defined as FVIII <1%) or moderately severe to severe hemophilia B (defined as FIX activity ≤2%) with or without inhibitors.
This cohort included 48 people living with hemophilia with inhibitors who were treated with HYMPAVZI during a 12-month active treatment period (ATP) versus an on-demand intravenous regimen with bypassing agents, administered as part of usual care in a six-month observational period. During the ATP, participants received prophylaxis (a 300 mg subcutaneous loading dose of HYMPAVZI, followed by 150 mg subcutaneously once weekly) with potential for dose escalation to 300 mg once weekly. An additional three patients in the inhibitor cohort were on routine prophylactic treatment prior to the study and not included in the primary efficacy analysis.
The primary endpoint measures the treated ABR during the 12-month ATP with HYMPAVZI compared to treated ABR on prior on-demand replacement therapy. For further information, visit clinicaltrials.gov.
About HYMPAVZI
HYMPAVZI has received regulatory approvals in the U.S. and in Europe for eligible patients living with hemophilia A without factor VIII inhibitors, or hemophilia B without factor IX inhibitors. HYMPAVZI was the first anti-TFPI approved in the U.S. and EU for the treatment of hemophilia A or B and the first hemophilia medicine approved in the U.S. and EU to be administered via a pre-filled, auto-injector pen. For eligible people living with hemophilia B, it is the first once-weekly subcutaneous prophylactic treatment. HYMPAVZI can offer a subcutaneous treatment option with a once-weekly dosing schedule and minimal preparation required for each individual administration.
Pfizer is also conducting BASIS KIDS, an open-label study investigating the safety and efficacy of HYMPAVZI in children 1 to <18 years of age with severe hemophilia A or moderately severe to severe hemophilia B with or without inhibitors.
About Hemophilia
Hemophilia is a family of rare genetic blood diseases caused by a clotting factor deficiency (FVIII in hemophilia A, FIX in hemophilia B), which prevents normal blood clotting. Hemophilia is diagnosed in early childhood and impacts more than 800,000 people worldwide.7 The inability of the blood to clot properly can increase the risk of painful bleeding inside the joints, which can cause joint scarring and damage. People living with hemophilia can suffer permanent joint damage following repeated bleeding episodes.9,10
For decades, the most common treatment approach for hemophilia A and B has been factor replacement therapy, which replaces the missing clotting factors. Factor replacement therapies increase the amount of clotting factor in the body to levels that improve clotting, resulting in less bleeding. The burden of intravenous infusions is believed to be a barrier to treatment adherence for some people living with hemophilia due in part to inconvenience, time constraints, and poor venous access.11
Approximately 20% of people with hemophilia A and 3% of people with hemophilia B are unable to continue taking factor replacement therapies because they develop inhibitors to FVIII and FIX.6 These patients often have higher treatment burden, including potential complications from bleeding such as hospitalization and death, as well as higher treatment-related costs.1,2,3,4,12
The full Prescribing Information can be found here.
About Pfizer: Breakthroughs That Change Patients’ Lives
At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world’s premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at www.Pfizer.com. In addition, to learn more, please visit us on www.Pfizer.com and follow us on X at @Pfizer and @Pfizer_News, LinkedIn, YouTube and like us on Facebook at www.facebook.com/Pfizer/.
1 Shapiro AD, Ragni MV, Borhany M, et al. Natural history study of factor IX deficiency with focus on treatment and complications (B-Natural). Haemophilia. 2021;27(1):49-59. doi: 10.1111/hae.14139.
2 Valentino LA, Ewenstein B, Navickis RJ, Wilkes MM. Central venous access devices in haemophilia. Haemophilia. 2004;10(2):134-46. doi: 10.1046/j.1365-2516.2003.00840.x.
3 Nugent D, Kalnins W, Querol F, et al. Haemophilia Experiences, Results and Opportunities (HERO) study: Treatment-related characteristics of the population. Haemophilia. 2015;21(1):e26-38. doi: 10.1111/hae.12545.
4 Soucie JM, Symons Jt, Evatt B, Brettler D, Huszti H, Linden J. Home-based factor infusion therapy and hospitalization for bleeding complications among males with haemophilia. Haemophilia. 2001;7(2):198-206. doi: 10.1046/j.1365-2516.2001.00484.x.
5 Teiu P, Chan A, Matino D. Molecular Mechanisms of Inhibitor Development in Hemophilia. Mediterr J Hematol Infect Dis. 2020 Jan 1;12(1):e2020001. doi: 10.4084/MJHID.2020.001.
6 Centers of Disease Control and Prevention. Testing for Inhibitors and Hemophilia. Accessed May 14, 2025. Available at: https://www.cdc.gov/hemophilia/testing/testing-for-inhibitors-and-hemophilia.html?CDC_AAref_Val=https://www.cdc.gov/ncbddd/hemophilia/inhibitors.html.
7 World Federation of Hemophilia. World Federation of Hemophilia Global Report on the Annual Global Survey 2022. https://www1.wfh.org/publications/files/pdf-2399.pdf.
8 Meeks S, Batsuli G. Hemophilia and inhibitors: Current treatment options and potential new therapeutic approaches. Hematology Am Soc Hematol Educ Program. 2016 Dec 2;2016(1):657–662. doi:10.1182/asheducation-2016.1.657.
9 Srivastava A, Santagostino E, Dougall A, et al. WFH guidelines for the management of hemophilia, 3rd Edition; 2020. Haemophilia. 26(S6), 1–158. https://doi.org/10.1111/hae.14046.
10 Franchini M, Mannucci PM. Past, present and future of hemophilia: A narrative review. Orphanet J Rare Dis. 2012;7:24. https://doi.org/10.1186/1750-1172-7-24.
11 Weyand AC, Pipe SW. New therapies for hemophilia. Blood. 2019;133(5):389–398. https://doi.org/10.1182/blood-2018-08-872291.
12 Walsh CE, Soucie JM, Miller CH. Impact of inhibitors on hemophilia a mortality in the United States. Am. J. Hematol. 2015; 90: 400-405. https://doi.org/10.1002/ajh.23957.
SOURCE: Pfizer
Post Views: 2,168
