The rebalancing agent concizumab has the potential to fulfil a need for new treatment options across all haemophilia subtypes but importantly for patients with haemophilia B and inhibitors.
Speaking at the ISTH Congress, Associate Professor Jan Astermark said that the US FDA had recently designated the high-affinity humanised monoclonal antibody as a breakthrough therapy for haemophilia B with inhibitors.
The drug targets the tissue factor pathway inhibitor (TFPI) and normalises thrombin generation.
Associate Professor Astermark, from the Centre for Thrombosis and Hemostasis at Sweden’s Lund University, presented the results of phase 2, dose escalation studies of once daily subcutaneous concizumab.
Explorer 4 comprised 26 patients with haemophilia A or B with inhibitors and the single arm Explorer 5 enrolled 36 patients with severe haemophilia A without inhibitors.
Patients were maintained on usual prophylaxis for the 4-8 weeks it took to reach a steady state concentration of concizumab with a loading dose of 1 mg/kg.
They were then escalated across doses of 0.15, 0.20 and 0.25 mg/kg concizumab if they experienced bleeding.
Associate Professor Astermark said concizumab reduced all bleeding, spontaneous and joint bleeding compared to recombinant factor VIIa on demand.
There were no safety signals other than mild adverse events and in particular, no thromboembolic events, fatal outcomes or events leading to treatment withdrawal.
Antibodies to the new compound were identified in six patients but with no observed clinical effect.
As evidence of acceptability and tolerability, all patients chose to continue onto the extension phase of the trials.
The optimised prophylactic dose for the phase 3 trials was determined to be 0.2 mg/kg or 0.2 ml for an 80 kg person.
The late-breaking research findings were determined to be one of the highlights amongst the bleeding-themed presentations at the Congress.