FDA Rejects Concizumab for Prophylactic Treatment of Hemophilia A, B

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The announcement resulted from the FDA’s request for manufacturing, administration, and patient monitoring information.

In its first-quarter earnings call, pharmaceutical company Novo Nordisk reported that the US Food and Drug Administration (FDA) has rejected the company's application for its investigational antibody, concizumab.1

The FDA asked for additional information about the drug's manufacturing process and the company's system “for monitoring and dosing patients to ensure that the treatment is administered correctly,” according to Martin Lange, Novo's Executive Vice President and Head of Development.

Concizumab has been proposed for prophylactic treatment of hemophilia A and B. The treatment is a monoclonal antibody that targets the tissue factor pathway inhibitor protein, which plays a role in coagulation.2

An anti-tissue factor pathway inhibitor (TFPI) antibody, conzizumab was designed as a once-daily prophylactic treatment that is also administered subcutaneously for every hemophilia type.

In July 2022, Novo posted positive phase 3 data from the Explorer7 trial that showed strong results for concizumab in reduction of spontaneous and traumatic bleeds

The data, which was presented at the International Society of Thrombosis and Haemostasis Annual Congress (ISTH 2022) last year, showed an 86% reduction in treated spontaneous and traumatic bleeds when those with inhibitors were on concizumab prophylaxis.

In 2020, Novo paused three concizumab trials after 3 patients developed non-fatal thrombotic events, and later resumed the phase 3 studies of the drug after working with regulatory authorities.

The hemophilia market is currently dominated by Roche's emicizumab (Hemlibra), a bispecific factor IXa- and factor X-directed antibody made to activate the natural coagulation cascade and restore the blood clotting process for those with hemophilia A.3


  1. Biospace. Novo Nordisk’s Hemophilia Hopeful Hits FDA Roadblock; Company Cuts Wegovy Supply. Biospace. May 3, 2023.
  2. Grossi, Giuliana. Concizumab Reduces Treated Bleeds in Hemophilia A or B with Inhibitors. HCPLive. July 15, 2022.
  3. Kunzmann, Kevin. Hemlibra Shows More Hemophilia A Efficacy After FDA Approval. HCPLive. November 20, 2017.