Novartis has bought the remaining rights to Arzerra from GlaxoSmithKline in a deal worth up to $1 billion.

The Swiss firm previously only acquired the rights to the drug’s cancer indications – which at the moment are limited to chronic lymphocytic leukemia – when it bought GSK’s oncology business in the companies’ asset-swap deal in March

But Arzerra (ofatumumab) is also being investigated in several other diseases, including multiple sclerosis (MS), which is Novartis’ main target in this deal.

"Novartis is pleased to further reinforce our commitment to neuroscience and to add an exciting new treatment to our strong MS portfolio," says David Epstein, head of Novartis Pharmaceuticals.

The treatment is a fully human monoclonal antibody that targets the CD20 protein. This causes the depletion of B cells, which are known to play an important role in MS.

Novartis’ MS portfolio also includes the strong-selling Gilenya (fingolimod), investigational treatments BAF312 and CJM112, and Glatopa – a generic version of Teva’s Copaxone (glatiramer acetate).

Under the terms of the agreement, Novartis will make an initial payment of $300 million to GSK for the acquisition with a further $200 million being payable following the start of a Phase III study in MS by the Swiss firm. The company may also pay up to $534 million in milestone payments to GSK, who are entitled to royalties of up to 12% of net sales of the drug in autoimmune conditions.