A partnership between Biogen Inc (NASDAQ:BIIB) and Ionis Pharmaceuticals Inc (NASDAQ:IONS) has received a milestone win in the Phase III data for nusinersen, a drug used to treat rare, severe genetic disease spinal muscular atrophy (SMA). The drug achieved significant improvement in motor milestone in treated versus untreated infant. Resulting from the positive data, Biogen paid Ionis $75 million fee so that it can exercise its option to develop and market nusinersen globally. It is expected that Biogen will start regulatory filling for nusinersen in the coming month. The drug is expected to become a blockbuster, with over $1 billion in annual sales.

As of now, there is no approved treatment for SMA, a disease that results in severe and progressive muscular atrophy and weakness. The most severe type usually results in paralysis and death. The disease affects over 25,000 people in the U.S. and stops many of them from working. Scientists’ understanding of the underlying genetic cause of the disease is fairly limited, a reason why drugs for the disease are only progressing through the pipeline of biotech and pharma companies.

Biogen will now pay for all the remaining clinical, regulatory and commercialization work. Ionis will still be responsible for the ongoing phase 3 studies before it transition everything to Biogen. It is estimated that Ionis can get up to $150 million as it continues with development of the drug. It would also get royalties on any sales of nusinersen.

Ionis chairman and CEO Stanley Crooke, noted that infants treated with nusinersen demonstrated a statistically higher significant improvement in the achievement of motor milestone as measured by Hammersmith Infant Neurological Examination, compared to those who did not get the receive the version. He further noted that responder analysis conducted, looked at achievement of tangible milestone including, rolling , head control, kicking , standing , crawling and in some events even walking.