Alnylam's hereditary disease treatment shows promise Mon Jul 16, 2012 12:07pm EDT (Reuters) - Alnylam Pharmaceuticals Inc said its experimental drug to treat an organ-damaging hereditary disorder showed promise in an early-stage trial by suppressing a protein that causes the disease. The company's shares rose 37 percent to a two-year-high of $17.23. The stock was the top percentage gainer on the Nasdaq. More than 3 million shares changed hands by noon, more than ten times their 50-day moving average volume. The drug aims to treat transthyretin-mediated amyloidosis (ATTR), a disease caused by mutations in the transthyretin (TTR) gene. "Suppression of TTR, the disease-causing protein in ATTR, was found to be rapid, dose-dependent, durable, and specific after just a single dose," Alnylam said in a statement. Alnylam also said there were no serious adverse events or discontinuations in the study. The main goal of the study was to evaluate the safety and tolerability of a single dose of the drug. The company has already begun a mid-stage study and expects to enroll about 20 patients. Alnylam develops drugs based on RNA interference, or RNAi -- a mechanism of silencing or turning on genes to prevent formation of proteins that can cause diseases. Reporting by Balaji Sridharan in Bangalore; Editing by Don Sebastian