Hereditary transthyretin-mediated amyloidosis (hATTR amyloidosis) is a rare, and previously untreatable, disorder caused by a faulty liver gene. The drug – Patisiran – 'silences' the gene without changing the patient's DNA, and is the first treatment of its type to be approved.
Professor Philip Hawkins, Head of the National Amyloidosis Centre at the Royal Free Hospital, London, said the approval by the National Institute for Health and Care Excellence (NICE) 'marks an important step forward in the treatment of a disease that is both life-threatening to patients and devastating to families.'
'Patisiran has shown in its main clinical study that it can halt or even improve potentially debilitating symptoms of this disease in the majority of patients. This means we now have a real possibility of preserving quality of life for eligible patients for longer than has so far been possible,' he said.
hATTR amyloidosis affects around 100 people in the UK and is caused by a mutation in the TTR gene that makes a protein called transthyretin. The abnormal protein builds up to toxic levels in tissues throughout the body, leading to damage of many organs and nerves. Patients may experience weakness or loss of sensation in the limbs, as well as problems with involuntary body functions related to heart rate, blood pressure and digestion.
Not everybody who has a TTR mutation will experience hATTR amyloidosis, but for those who do, symptoms can begin between the ages of 20-70, and the disease can prove fatal within three to 15 years.
Patisiran uses an RNAi (RNA interference) approach to inactivate the messenger RNAs that copy the faulty gene and act as templates to make the mutated protein. In the previous clinical trial, 56 percent of the 225 patients treated with the drug showed an improvement in symptoms, compared with four percent of patients treated with placebo. A further follow-up study over a period of 36 months suggested that this improvement was maintained.
Professor Julian Gillmore, also of the National Amyloidosis Centre, called news of the approval 'exciting' and told the BBC that gene-silencing has 'very far-reaching potential'.
One of the main drawbacks of such treatments is the cost. Patisiran is estimated to cost around £300,000 a year per patient, with the drug having to be administered once every three weeks by intravenous infusion. Despite this, scientists hope to continue transforming gene-silencing into novel medicines to improve the lives of patients affected by rare and severe diseases.
'Gene-silencing is a promising area of medicine and it is heartening to see this science translating into treatments that can potentially help those suffering from serious illnesses like hATTR amyloidosis,' Professor Hawkins concluded.