Trials of a new gene treatment have shown that it can reverse the effects of the porphyria. This disease is popularly thought to have been the cause of “The Madness of George III” although more recently it is believed he had extreme bipolar disorder. The new treatment could be the first in a whole class of new drugs. Instead of changing the patient’s DNA, this blocks the effect of a gene.
In this case the gene targetted controls the production of a component of blood called haem,a component of haemoglobin. With insufficient produced, toxins build up and patients can experience episodes of extreme pain in their joints. In others there are skin problems. Extreme cases can cause paralysis or death.
This “gene silencing” technique involves monthly injections of a drug called givosiran but has been remarkably effective. The BBC interviewed one of the patients in the trial that covered 18 countries and involved 94 triallists.
Sue Burrell, from Norfolk, has endured pain few could imagine and needed to take strong opioid painkillers every day.
At one point her porphyria was causing severe attacks every couple of weeks and needed hospital treatment.
But even then morphine did not stop the pain.
She told the BBC it was worse than child-birth, saying: "It's so intense - so strong it's in your legs, in your back, and it just resonates everywhere. It's really, really unbearable."
In the trial, severe attacks were cut by 74%. 50% of those given the treatment did not need hospital treatment for an attack during the trial compared to 14% given the placebo. (One dropped out because of side effects.) Sue no longer needs painkillers.
There are experiments using “gene silencing” for other illnesses. Carlos Heras-Palou, an orthopaedic surgeon at Royal Derby Hospital, had his transthyretin-mediated amyloidosis (hATTR amyloidosis) treated in a trial of a gene blocking drug called patisiran. A drug developed by Ionis Pharmaceuticals and now licenced to Roche has been used to treat Huntingdon’s in trials. It’s even been suggested as a means of lowering cholesterol.
The inital problem will be one of cost. A convertional gene-altering therapy for a rare condition causing blindness has been priced at $425,000 per eye forthe one-off injection. Mr Heras-Palou’s continued treatment will be free as a triallist but the drug is expected to cost $400,000 per patient per year. The question for this treatment will be how much the cost of treating acute episodes and giving powerful opioids compares to the cost of the new drug and its savings.