FRONTIER4 trial

Background

Open-label phase 3 extension study (FRONTIER4); interim 26-week analysis of the once-every-2-weeks arm (N=37). Hemophilia A with or without inhibitors, age ≥12 yr, rolled over from the denecimig phase 2 study (mean prior denecimig exposure 1.73 yr). Denecimig (Mim8) is a next-generation activated-FVIII-mimetic, fully human bispecific IgG4 antibody (emicizumab class) given subcutaneously.

Results

Interventions and follow up: Arm A: Denecimig SC once every 2 weeks, weight-tiered dosing, x26 wk (single-arm extension)
Arm B: None (open-label extension)
Primary endpoint: Number of treatment-emergent adverse events
mFollow up: 26 wk
Results: Estimated mean ABR (treated bleeds): 0.38 bleeds/patient-year
Zero treated bleeds: 83.8% of patients
Denecimig plasma concentrations: stable through wk 26
Anti-denecimig antibodies: NR

Adverse events

TEAEs: 60 events in 20/37 patients; 98.3% mild/moderate; 75.0% judged unlikely related
Injection-site reactions: 14 events in 2 patients
Discontinuations or fatal events: none

Conclusions

Every-2-weeks denecimig maintained near-zero bleeding (ABR 0.38; 84% with zero treated bleeds) over 26 weeks with no new safety signals, supporting flexible-interval subcutaneous prophylaxis with this next-generation FVIIIa mimetic in hemophilia A with or without inhibitors.

Key Limitations

Single-arm open-label extension with no comparator; very small (N=37), highly selected population of phase 2 completers already tolerating denecimig; 26-week interim analysis only; primary endpoint is safety-based, so efficacy data are descriptive.

Clinical Context

The pivotal FRONTIER2 trial (NEJM 2026) showed denecimig prophylaxis superior to on-demand treatment and factor prophylaxis for annualized bleeding rate; a BLA was filed with FDA in 2025 spanning weekly, every-2-weeks, and monthly dosing. If approved, denecimig would compete directly with emicizumab, offering more flexible intervals and a prefilled pen-injector.

References