# Factor VIII in vitro bioequivalence of denecimig (Mim8) hemostatic effect by thrombin generation assays

## TL;DR

This study compares how well denecimig, a new treatment for hemophilia A, can help with blood clotting compared to another drug, emicizumab, using lab tests.

## Contribution

The study introduces a novel in vitro assessment of denecimig's hemostatic activity using thrombin generation assays under various trigger conditions.

## Key findings

- Denecimig showed higher FVIII bioequivalence than emicizumab-SIA in thrombin generation assays.
- FVIII bioequivalence estimates varied depending on the TGA parameter and trigger type and concentration.
- Denecimig demonstrated a higher thrombin peak in conditions with limited activated FIX compared to emicizumab-SIA.

## Abstract

Denecimig (Mim8, Novo Nordisk A/S) is a next-generation bispecific antibody designed to mimic activated factor (F)VIII and restore hemostasis in persons with hemophilia A. The extent to which activated FVIII mimetics, such as denecimig and emicizumab, can correct clotting deficiency remains unclear.

To assess the in vitro FVIII bioequivalence of denecimig hemostatic activity using thrombin generation assays (TGAs).

Thrombin generation was analyzed in severe hemophilia A platelet-poor plasma, spiked with various levels of FVIII or with clinical doses of denecimig (5 μg/mL) or emicizumab (50 μg/mL), using a sequence-identical analog (SIA). TGA used 4 trigger conditions: tissue factor (TF), activated FXI, a combination of TF and activated FXI, or activated FIX.

The average FVIII bioequivalence estimate using 1 pM TF trigger was 42 IU/dL (SD, 14) for 5 μg/mL denecimig and 14 IU/dL (SD, 5) for 50 μg/mL emicizumab-SIA using peak thrombin. The FVIII bioequivalence estimates of denecimig and emicizumab-SIA for hemostatic activity were generally highest for endogenous thrombin potential, followed by peak thrombin and velocity index across trigger concentrations. FVIII bioequivalence increased with decreasing trigger concentrations. Denecimig demonstrated a higher thrombin peak in conditions with limited activated FIX compared with emicizumab-SIA, suggesting differences in mechanisms of action.

Estimation of denecimig in vitro FVIII bioequivalence with TGA depends on the TGA parameter and the type and concentration of the trigger. Denecimig demonstrated higher in vitro FVIII bioequivalence than emicizumab-SIA, indicating the potential for effective hemostatic coverage. Further studies are needed to fully understand the hemostatic effects of bispecific antibodies.

•The degree of clotting correction by activated FVIII mimetics for hemophilia A remains unclear.•In vitro FVIII bioequivalence of denecimig activity was assessed by TGA.•Denecimig demonstrated higher FVIII bioequivalence than a sequence-identical analog of emicizumab.•Estimation of FVIII bioequivalence depends on the TGA parameter and the trigger type and concentration.

The degree of clotting correction by activated FVIII mimetics for hemophilia A remains unclear.

In vitro FVIII bioequivalence of denecimig activity was assessed by TGA.

Denecimig demonstrated higher FVIII bioequivalence than a sequence-identical analog of emicizumab.

Estimation of FVIII bioequivalence depends on the TGA parameter and the trigger type and concentration.