Pfizer has shared positive top-line results from a late-stage study of its haemophilia A and B therapy Hympavzi (marstacimab).
The phase 3 BASIS trial has been evaluating the drug in adult and adolescent patients with inhibitors, or antibodies, which neutralise factor replacement therapies and make them ineffective.
The study met its primary endpoint, with once-weekly prophylactic treatment with Hympavzi resulting in a statistically significant and clinically relevant reduction in annualised bleeding rate (ABR) of treated bleeds compared to on-demand treatment.
Patients were treated with Hympavzi during a 12-month period versus an on-demand intravenous regimen with bypassing agents, given as part of usual care in a six-month lead-in period.
Hympavzi reduced ABR by 93% over 12 months and also demonstrated superiority across all bleeding-related secondary endpoints, including spontaneous bleeds, joint bleeds, target joint bleeds and total bleeds.
Over 800,000 people worldwide are affected by haemophilia, a group of rare genetic blood disorders caused by a clotting factor deficiency. Alongside episodes of excessive and prolonged bleeding, patients can experience spontaneous bleeding in their joints and muscles without having had an injury, potentially leading to joint damage.
Pfizer’s Hympavzi, given as a once-weekly subcutaneous injection using a pre-filled pen, works by reducing the amount of TFPI, a naturally occurring protein that prevents blood from clotting too much. This promotes the formation of thrombin, an enzyme critical in blood clotting.
The drug already holds approvals to treat haemophilia A and B patients without inhibitors. However, around 20% and 3% of haemophilia A and B patients, respectively, are unable to continue taking factor replacement therapies because they develop inhibitors to factor VIII and factor IX.
Michael Vincent, chief inflammation and immunology officer at Pfizer, said: “These encouraging results demonstrate Hympavzi’s potential to help people living with haemophilia A or B with inhibitors, meeting an important need for patients with antibodies that neutralise most factor-based prophylactic options used to manage bleeding episodes.”
Pfizer said it is planning to discuss the latest results with regulatory authorities, “with the goal of initiating regulatory filings for Hympavzi for the treatment of patients living with haemophilia with inhibitors”.
