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Presentation Details
| Outcomes by Dose Escalation Criteria in Participants With Hemophilia A or B Without Inhibitors Receiving Marstacimab in the BASIS Trial Laurent Frenzel1, Travis Gould2, Pengling Sun3, Andrew Palladino4, Oliver Glass3. 1Department of Haematology, Hemophilia Care and Research, Necker Hospital, Institut Imagine, Paris, France.2Pfizer Inc, New York, NY, USA.3Pfizer Inc, Cambridge, MA, USA.4Pfizer Inc, Collegeville, PA, USA |
Abstract
Background: Marstacimab efficacy was demonstrated in participants with hemophilia A (HA) or B (HB) with or without inhibitors in the phase 3 BASIS study (NCT03938792). Objective: To evaluate outcomes in participants without inhibitors who met criteria for dose escalation (DE). Methods: Participants without inhibitors were categorized by factor replacement treatment (on-demand [OD] or routine prophylaxis [RP]) in a 6-month observational phase (OP). Participants received a single subcutaneous marstacimab 300-mg dose (2x 150-mg injections) followed by once-weekly (QW) 150 mg in the 12-month active treatment phase (ATP). Participants who completed the ATP could enroll in the open-label extension (OLE). Dose could be increased at investigator discretion to 300 mg QW after Day 180 for participants who met protocol-specified criteria (weight ≥50 kg, ≥2 spontaneous bleeds requiring treatment in 6 months). Annualized bleeding rates (ABR) are summarized for participants without inhibitors. A proprietary generative AI tool was used with author review to develop the first draft; authors take full responsibility for the content. Results: Overall, 128 participants (median age 30 [range 13–66] years) without inhibitors entered OP, 116 entered ATP (RP: n=83, OD: n=33; mean [range] duration: 12 [1–13] months); 107 continued in OLE (data cutoff: October 2023; RP: n=75, OD: n=32; duration: 12 [1–23] months). In the OP, mean (95%CI) ABR was 7.9 (5.1–10.6) vs 38.0 (31.0–46.5) for RP vs OD participants. Of 47 participants (40.5%; RP: n=33; OD: n=14) who qualified for DE in BASIS, 14 (RP: n=11; OD: n=3) increased dose in ATP. The median (range) body weight was 70.7 kg (35.0–120.0 kg) for the overall population, 76.3 kg (42.3–102.0 kg) for the 22 RP participants who qualified for DE but did not DE, 63.3 kg (44.8–84.0 kg) for the 11 RP participants who DE, 75.2 kg (46.4–114.0 kg) for the 11 OD participants who qualified for DE but did not DE, and 73.0 kg (71.5–112.0 kg) for the 3 OD participants who DE. For RP participants, ABR improved early after DE: mean (95%CI) was 14.0 (3.8–24.3) in OP, 14.1 (9.0–19.2) in ATP before DE, 3.3 (1.4–5.2) in ATP after DE, and 4.9 (1.8–8.0) in OLE. For RP participants who did not DE, ABR improved into OLE: mean (95%CI) was 10.2 (4.2–16.2) in the OP, 9.6 (5.7–13.6) in ATP, and 6.1 (1.9–10.4) in OLE. For OD participants who did not DE, ABR improved in ATP and was maintained in OLE: mean (95%CI) was 45.8 (34.4–61.2) in OP, 4.2 (3.1–5.7) in ATP, and 4.2 (2.3–7.6) in OLE (data not estimated for DE OD participants due to limited sample size). No safety concerns were associated with DE. Conclusions: Marstacimab DE led to rapid ABR reduction, which may improve outcomes in participants without inhibitors with a greater number of bleeds. There was no noticeable relationship between body weight and DE. ABR decreased over time in participants without inhibitors who met DE criteria but remained on 150 mg.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.