INDIRECT TREATMENT COMPARISON OF MARSTACIMAB VERSUS FITUSIRAN ANTITHROMBIN-BASED DOSE REGIMEN AMONG INDIVIDUALS WITH HEMOPHILIA A/B, WITHOUT INHIBITORS, WHO PREVIOUSLY RECEIVED ON-DEMAND THERAPY
Author(s)
Shuiqing ZHU, MS1, Peng Dong, PhD1, Maria Gheorghe, PhD2, Mónica Sofia Inês, PhD2, Hae Kyung Kim, PhD2, Joseph C. Cappelleri, PhD2, Haitao Chu, PhD, MD2, Tommy Lan, MSc3, Kristina B. Lindsley, PhD4, Devon J. Boyne, PhD3.
1Pfizer, Beijing, China, 2Pfizer, New York, NY, USA, 3IQVIA, Kirkland, QC, Canada, 4IQVIA, Falls Church, VA, USA.
1Pfizer, Beijing, China, 2Pfizer, New York, NY, USA, 3IQVIA, Kirkland, QC, Canada, 4IQVIA, Falls Church, VA, USA.
OBJECTIVES: Marstacimab is a new treatment for hemophilia A/B that was shown to reduce bleeding rates relative to factor replacement in the Phase 3 BASIS trial (NCT03938792). Fitusiran is a non-factor treatment for hemophilia A/B recently assessed in the Phase 3 ATLAS-OLE open-label extension study through an antithrombin-based dose regimen (AT-DR) (NCT03754790). An indirect treatment comparison was conducted to estimate the relative efficacy in treated annualized bleeding rates (ABRs) of marstacimab versus fitusiran among males aged ≥12 years with hemophilia A/B without inhibitors who received prior on-demand therapy.
METHODS: We leveraged individual-level data from BASIS as well as aggregate-level outcome and baseline data from ATLAS-OLE, respectively. To align with the follow-up of ATLAS-OLE, BASIS data were restricted to 196 days of follow-up. Unanchored simulated treatment comparison (STC) was used to compare treatments after adjusting for differences in mean age, body weight, and prior bleeding events. Rate ratios (RRs) and 95% confidence intervals (CIs) were estimated for treated ABRs.
RESULTS: The analyses included 33 patients from BASIS and 80 from ATLAS-OLE. After STC-adjustment, marstacimab remained significantly associated with lower treated ABRs (adjusted RR: 0.23 [0.08, 0.70]; two-sided p=0.01) corresponding to an approximately 77% reduction in treated ABR. The STC results of treated joint bleeding and treated spontaneous bleeding were both statistically significantly lower than Fitusiran.
CONCLUSIONS: These findings, based in the context of an unanchored ITC, suggest that marstacimab significantly improves bleeding rates relative to fitusiran for patients with hemophilia A/B without inhibitors who received prior on-demand therapy. Since we were unable to adjust for baseline imbalances in the percent of patients with any target joints in BASIS (n=33/33; 100%) versus ATLAS-OLE (n=53/80; 66.3% - indicating worse joint status for BASIS), the relative benefit of marstacimab may have been underestimated.
METHODS: We leveraged individual-level data from BASIS as well as aggregate-level outcome and baseline data from ATLAS-OLE, respectively. To align with the follow-up of ATLAS-OLE, BASIS data were restricted to 196 days of follow-up. Unanchored simulated treatment comparison (STC) was used to compare treatments after adjusting for differences in mean age, body weight, and prior bleeding events. Rate ratios (RRs) and 95% confidence intervals (CIs) were estimated for treated ABRs.
RESULTS: The analyses included 33 patients from BASIS and 80 from ATLAS-OLE. After STC-adjustment, marstacimab remained significantly associated with lower treated ABRs (adjusted RR: 0.23 [0.08, 0.70]; two-sided p=0.01) corresponding to an approximately 77% reduction in treated ABR. The STC results of treated joint bleeding and treated spontaneous bleeding were both statistically significantly lower than Fitusiran.
CONCLUSIONS: These findings, based in the context of an unanchored ITC, suggest that marstacimab significantly improves bleeding rates relative to fitusiran for patients with hemophilia A/B without inhibitors who received prior on-demand therapy. Since we were unable to adjust for baseline imbalances in the percent of patients with any target joints in BASIS (n=33/33; 100%) versus ATLAS-OLE (n=53/80; 66.3% - indicating worse joint status for BASIS), the relative benefit of marstacimab may have been underestimated.
Conference/Value in Health Info
2026-09, ISPOR Asia Pacific 2026, Bangkok, Thailand
Value in Health, Volume 55, Issue S1
Code
CO11
Topic
Clinical Outcomes
Topic Subcategory
Comparative Effectiveness or Efficacy
Disease
SDC: Systemic Disorders/Conditions (Anesthesia, Auto-Immune Disorders (n.e.c.), Hematological Disorders (non-oncologic), Pain)