Emicizumab improves coagulation potential in plasma from infants and toddlers with hemophilia A, according to research published in Pediatric Blood & Cancer.

Investigators conducted a study of in vitro or in vivo coagulation potential of emicizumab in plasmas obtained from previously untreated and minimally treated infants and toddlers with severe hemophilia A.

The plasmas were incubated with emicizumab (50 μg/mL) and the coagulant effect was measured as the adjusted maximum coagulation velocity (Ad|min1|) by clot waveform analysis and peak thrombin by thrombin generation assay. The plasmas of patients who had been treated with factor (F)VIII products or emicizumab (in vivo cases) were preincubated with anti-FVIII or anti-emicizumab, respectively, monoclonal antibody prior to further incubation with emicizumab.

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A total of 27 plasma samples were obtained from 14 patients, with median age of 19 months (range, 0-42 months) who received emicizumab (n = 9), factor (F)VIII products (n = 8), or no treatment (n = 10).

Emicizumab improved Ad|min1| values in 24 samples (88%), from 3.10 ± 0.08 to 3.89 ± 0.08 (P <.01) in in vitro cases and from 3.49 ± 0.16 to 4.60 ± 0.23 (P <.01) in in vivo cases. Emicizumab improved peak thrombin in 20 samples (74%), from 16.6 ± 1.9 to 95.7 ± 18.2 nM (P < .01) in in vitro cases and from 25.7 ± 5.6 to 181.9 ± 19.3 nM (P <.01) in in vivo cases.

Overall, the study found that emicizumab-dependent increases in both Ad|min1| and peak thrombin occurred in 18 samples, while increases in either parameter occurred in 8 samples. A single sample from a patient 1 month of age showed no increase in either measure.

“Our present findings suggest that emicizumab possibly enhances coagulant potential even at very young ages, although this coagulant potential appeared to vary and depends on the individual sample properties,” the study authors concluded. “The impact of age remains fully investigated, but our findings suggest that emicizumab may be most effective in older infants whose coagulant and anticoagulant factors are becoming similar to those in adults.”

Disclosure: This research was supported by Chugai Pharmaceutical Co., Ltd. Please see the original reference for a full list of disclosures.


Takeyama M, Matsumoto N, Abe H, et al. Coagulant potentials of emicizumab in the plasmas from infant and toddler patients with hemophilia A. Pediatr Blood Cancer. Published online July 19, 2023. doi:10.1002/pbc.30590