Shares in Alnylam were on the rise after it emerged that its Genzyme-partnered amyloidosis RNAi therapeutic revusiran has been granted Orphan drug status in the US.

The drug, which is intended for the treatment of transthyretin-mediated amyloidosis (ATTR amyloidosis), is currently being assessed in Phase III development for Familial Amyloidotic Cardiomyopathy, one of the predominant clinical manifestations of the condition.

ATTR amyloidosis is an inherited, progressively debilitating, and often fatal disease caused by mutations in the TTR gene. The rare and aggressive protein mis-folding disorder is characterised by the deposition of amyloid in bodily organs and tissues such as the heart and kidneys and represents a major unmet medical need.

FAC affects around 40,000 people worldwide and the prognosis is poor, with life expectancy just 2.5 to 5 years from diagnosis, and treatment is currently limited to supportive care.

Revusiran picked up orphan status in Europe in April last year.