Isis Pharmaceuticals, Inc. (ISIS), a company engaged in the discovery and development of antisense drugs using novel drug discovery platform, has earned a $2 million milestone payment from Biogen Idec related to the advancement of the ongoing open-label extension study of ISIS-SMNRx in children with spinal muscular atrophy (SMA).

The open-label extension study of ISIS-SMNRx is offered to those children with SMA who have completed dosing in Isis' previous studies.  In this study, children with SMA are receiving a 12 mg dose of ISIS-SMNRx every six months for the duration of the study.  

ISIS-SMNRx is designed to alter the splicing of a closely related gene (SMN2) to increase production of fully functional SMN protein.  The United States Food and Drug Administration granted orphan drug status and fast track designation to ISIS-SMNRx for the treatment of patients with SMA.  Isis is currently in collaboration with Biogen Idec to develop and potentially commercialize the investigational compound, ISIS-SMNRx, to treat all types of SMA.  

Under the terms of the January 2012 agreement, Isis is responsible for global development and Biogen Idec has the option to license the compound until completion of the first successful phase 2/3 study or the completion of two phase 2/3 studies.

Isis acknowledges support from the following organizations for ISIS-SMNRx: Muscular Dystrophy Association, SMA Foundation, Families of SMA and intellectual property licensed from Cold Spring Harbor Laboratory and the University of Massachusetts Medical School.

SMA is a severe genetic disease that affects approximately 30,000-35,000 patients in the United States, Europe and Japan. SMA is caused by a loss of, or defect in, the survival motor neuron 1 (SMN1) gene leading to a decrease in the survival motor neuron (SMN) protein. SMN is critical to the health and survival of nerve cells in the spinal cord responsible for neuromuscular growth and function. One in 50 people, the equivalent of about 6 million people in the United States, are carriers of a defective SMN1 gene, which is unable to produce fully functional SMN protein. Carriers experience no symptoms and do not develop the disease. However, when both parents are carriers, there is a one in four chance that their child will have SMA. The severity of SMA correlates with the amount of SMN protein. Infants with Type I 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 greater amounts of SMN protein but still have a shortened lifespan and are never able to stand independently. Children with Type III have a normal lifespan but accumulate life-long physical disabilities as they grow.