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(96) Factor VIII exposure analysis from HAVEN 7: emicizumab in infants with severe hemophilia A

Location: Exhibit Hall D

    Co-Author Not Presenting(s)

  • Guy Young, MD

    Director
    Children’s Hospital Los Angeles
    Los Angeles, California, United States

    • First Author Presenting(s)

  • Elise Lim, PhD

    Senior Statistical Scientist
    Genentech, Inc.
    San Francisco, California, United States

    • Co-Author Not Presenting(s)

  • Katherine Eakle, Pharm.D.

    Senior Medical Science Director
    Genentech, Inc.
    South San Francisco, California, United States

Title: Factor VIII exposure analysis from HAVEN 7: emicizumab in infants with severe hemophilia A

Abstract : Basis of inquiry: HAVEN 7 (NCT04431726) showed that emicizumab was efficacious and well tolerated in infants with severe hemophilia A (HA) without factor (F)VIII inhibitors.

Objective: To explore total FVIII exposure days (EDs) before and during HAVEN 7, and contextualize two incidences of inhibitor development.

Methods: Previously untreated/minimally treated participants (MTPs; ≤5 EDs with FVIII-containing treatment) with no history of inhibitors were eligible. Inhibitors were assessed (via chromogenic Bethesda assay) in MTPs at baseline, and any infant during the study after 3 FVIII EDs or ≥2 consecutive FVIII doses.
Findings: Fifty-five male infants had received emicizumab for ≥52 weeks at cut-off (May 22, 2023; median [range] duration: 100.3 [52–118] weeks). Pre-study, 30 (54.5%) infants had ≥1 FVIII ED, median (range) was 1 (0–6) day. Median (range) number of on-study FVIII EDs was 1 (0–10). Forty-four (80.0%) infants had ≥1 FVIII ED since birth: 27 (49.1%) had 1–3 EDs, 12 (21.8%) had 4–6 EDs, 3 (5.5%) had 7–9 EDs, and 2 (3.6%) had 10–13 EDs. Median (range) total FVIII EDs was 2 (0–13). Seven (12.7%) infants had family history of inhibitors.
Two infants developed FVIII inhibitors. One participant (large F8 deletion; no history of inhibitors) developed an inhibitor after three nonconsecutive EDs for two traumatic mouth bleeds. Another (intron 22 inversion; family history of inhibitors) developed an inhibitor after 10 nonconsecutive EDs for a traumatic mouth bleed and surgical procedures (adenoidectomy and tonsillectomy).

Conclusions: Although 44/55 (80%) infants receiving emicizumab had ≥1 FVIII ED since birth, 69% had ≤3 EDs, with 2 (3.6%) developing inhibitors. More time is needed to determine inhibitor rate in people who begin emicizumab as infants. Participants will continue emicizumab during a 7-year long-term follow-up, providing data on rate, timing, and risk factors for inhibitor development in this population.