 This makes it more likely for the siRNA to cause an immunostimulant response in the event of the pathogen.Clinical Phase I and II studies of siRNA therapies conducted between 2015 and 2017 have demonstrated potent and durable gene knockdown in the liver, with some signs of clinical improvement and without unacceptable toxicity.Two Phase III studies are in progress to treat familial neurodegenerative and cardiac syndromes caused by mutations in transthyretin (TTR).