Roche has presented a new batch of data showing that its experimental bispecific monoclonal antibody emicizumab significantly reduced bleeds in patients with haemophilia A and inhibitors to factor VIII.

The Phase III HAVEN 1 study compared the prophylactic use of emicizumab compared with on-demand and prophylactic use of bypassing agents (BPAs) in adults and adolescents with haemophilia A resistant to standard treatment; results showed a statistically significant and clinically meaningful reduction in bleed rate of 87 percent with Roche’s drug.

After a median observation time of 31 weeks, 62.9 percent of patients receiving emicizumab experienced zero treated bleeds compared to 5.6 percent of those receiving on-demand BPAs.

Reduction in bleed rate with the drug was consistent across all secondary endpoints, including all bleeds (80 percent), treated spontaneous bleeds (92 percent), treated joint bleeds (89 percent) and treated target joint bleeds (95 percent) compared with on-demand BPAs.

On the safety side, adverse events (AEs) occurring in 5 percent or more of patients treated with emicizumab were injection site reactions, headache, fatigue, upper respiratory tract infection and arthralgia, the firm noted.

Serious side AEs of thromboembolic events and thrombotic microangiopathy occurred in two patients and three patients*, respectively, while receiving emicizumab prophylaxis, but this was linked with repeated high doses of BPAs used to treat breakthrough bleeds.

Meanwhile, interim results from the single arm HAVEN II study in children younger than 12 years of age with haemophilia A with inhibitors who received emicizumab prophylaxis are consistent those observed in HAVEN I, Roche said.

After a median observation time of 12 weeks, the study showed that only one of 19 children receiving emicizumab reported a treated bleed, and there were no reported joint or muscle bleeds.

The data also indicate that the same dose of emicizumab is appropriate for children as for adults and adolescents.

Emicizumab is expected to filed in the US this year for haemophilia A patients with inhibitors to Factor VIII inhibitors in the first instance, and some analysts have predicted peak sales of $5 billion if it makes it to market.

However, others fear that its success could be hampered by the potential need for doctors to keep a very close eye on the concurrent use of BPAs.