Emicizumab Dosage

Emicizumab provides effective prophylaxis for hemophilia A (HA), but its cost puts a burden on health care systems. Pharmacokinetic (PK)-pharmacodynamic analyses suggest that emicizumab is effective at lower trough concentrations (Ctrough) than the mean 55 μg/mL reported with conventional dosing.

To perform an interim analysis comparing bleeding control during 6 months of conventional emicizumab dosing vs PK-guided dosing in participants with HA, targeting a Ctrough of 25-35 μg/mL.

The DosEmi study (NCT06320626) is an ongoing multicenter, open-label, crossover Dutch trial. Eligible participants were aged ≥16 years using emicizumab for ≥12 months with good bleeding control (≤2 treated bleeds/6 months, none spontaneous). This planned interim analysis compared 6 months’ bleeding on conventional dosing with PK-guided dosing. Study continuation criteria were ≤15% decrease in the proportion of participants without treated bleeds, maximum of 2 spontaneous bleeds overall, and <1.0 increase in bleeds/y (annualized bleeding rate).

In 26 participants with severe HA, PK-guided dosing reduced emicizumab consumption by 39% (range, 13%-50%). The proportion of participants without treated bleeds was 69% with conventional dosing vs 58% with PK-guided dosing (risk difference, +11%; P = .254); the proportion without joint bleeds remained stable at 85% vs 88%, respectively (risk difference, −4%; P = .500). The annualized bleeding rate remained low (0.7 vs 0.9; P = .132), including 1 spontaneous muscle bleed (emicizumab concentration 52.5 μg/mL).

These interim results suggest that bleeding control with PK-guided reduced emicizumab dosing (target Ctrough 25-35 μg/mL) is similar to conventional dosing. All prespecified criteria for study continuation and inclusion of participants aged <16 years were met.