Biogen Idec is to collaborate with Isis Pharmaceuticals to develop its early-stage antisense drug for the treatment of spinal muscular atrophy in a deal that could be worth almost $300 million to the latter firm.

Under the terms of the deal, Biogen will pay $29 million upfront to Isis, which is also eligible to receive up to $45 million in milestone payments. The biotech major has an option to license ISIS-SMNRx until completion of the first successful Phase II/III trial, and Isis could bank up to another $225 million, plus double-digit royalties.

SMA is a severe genetic disease that affects approximately 30,000-35,000 patients in the USA, Europe and Japan. It is caused by a defect in the survival motor neuron 1 gene leading to a decrease in the survival motor neuron protein, which is critical to the health of nerve cells in the spinal cord responsible for neuromuscular growth and function.

Infants with type 1 SMA, the most severe form of the disease, produce very little SMN protein and have a life expectancy of less than two years. Children with type II have a shortened lifespan and are never able to stand independently, while those with type III have a normal lifespan but accumulate life-long physical disabilities as they grow.

ISIS-SMNRx, which has been granted orphan drug status and fast-track designation by the US Food and Drug Administration, went into Phase I trials last month. Commenting on the deal, Biogen chief executive George Scangos said SMA is "a heartbreaking disease – it can kill children before their second birthday and there are currently no therapies to treat the disease”.

He added that “it is exactly the kind of disease and programme that we are focused on [as] the unmet need could not be any greater". Isis’ antisense compound "has the potential to be a highly effective, first-to-market therapy for this deadly disease", Dr Scangos concluded.

Other companies are also developing drugs to treat SMA, notably Roche which teamed up with PTC Therapeutics in a deal that could be worth $490 million to the latter. Other firms looking at the disorder include RepliGen, while the SMA Foundation, which has worked with Isis and PTC, is also collaborating with Novartis.