Bayer has linked up with Dimension Therapeutics to develop a gene therapy for haemophilia A in a deal that could be worth about $250 million to the US biotech.

The German group has long been a major player in haemophilia A with its recombinant factor VIII (rFVIII) blockbuster Kogenate and earlier this year it unveiled plans to invest more than 500 million euros at two manufacturing sites to prepare for the production of two investigational treatments for the bleeding disorder. Now it will have access to a therapy “with the potential to significantly change the treatment landscape",  according to Dimension chief executive Thomas Beck.

Dr Beck noted that currently-available replacement therapies for haemophilia A are often administered intravenously “multiple times a week and may be required for life, depending on the severity of a patient’s disease”. He added that inserting a correct version of the faulty gene responsible for the disorder could be transformational.

Dimension says that its adeno-associated virus vector technology allows for systemic intravenous administration of the clotting factor gene in vivo, which has been shown in preclinical studies to target the liver “resulting in long-lasting expression of FVIII protein at therapeutic levels”.

Cashwise, Bayer is making an upfront fee of $20 million and potential development and commercialisation milestone payments of up to $232 million, plus royalties. Dimension, which was only formed in 2013, will be responsible for all pre-clinical development activities and the Phase I/IIa study, with funding from Bayer, which will take over from there.

The bleeding disorder, which is largely inherited, has been attracting new players into the field of late. Biogen Idec received US approval earlier this month for its haemophilia A drug Eloctate (antihaemophilic factor [recombinant] Fc fusion protein) and for Alprolix (recombinant factor IX Fc fusion protein) for haemophilia B in March.