The historic news of a breakthrough in the treatment of Huntington’s disease (HD) has caused excitement worldwide, and for good reason. It is the first time any drug has lowered the levels of the faulty protein known to cause the disease and consequently, it is hoped, will improve the devastating cognitive, mental health and motor symptoms that result. The joy among people living with conditions is palpable, but what will this really mean for them in the coming years?

This drug trial was not designed to evaluate the impact on symptoms essentially it aimed to discover if the drug is safe; the first cause for celebration is that the drug appears very safe. Patients received the drug for only a few months and HD progresses slowly over fifteen to twenty years; it was too short a time to measure any difference. In the next step Swiss company Roche will lead a phase three trial which will last two to three years and its aim is to establish what impact this drug has on symptoms. If it is successful, the drug will have to be licensed by the European Medicines Agency and approved for use in the NHS by the Scottish Medicine’s Consortium. An optimistic appraisal suggests five to seven years from now, the drug may be available to treat people with HD.

An immediate question on the minds of people with HD and their families is, “How can I participate in the next trial.” It is too early to answer this question. Roche needs around 300 people to participate and in the next few months it will recruit research sites across the world. We do not know if any will be in Scotland. Clinical trials have eligibility criteria; the phase one trial focussed on people with early symptoms of Huntington’s. Roche have yet to announce any details of the phase three trial, but certainly not everyone will be eligible to participate.

If the drug, called IONIS-HTTRX, is successful it will most benefit people with early stage HD. This is because, as the condition progresses, it causes brain cell death which cannot be reversed; earlier on, sick brain cells may be ‘rescued’. This means perhaps two thirds of people with HD may not benefit from treatment and it is crucial that we continue to invest in much needed care and support; in the excitement of this new therapy, they must not be forgotten. Ethical issues around who should be treated will present new dilemmas for families to face.

For those that may benefit, they will require monthly to three monthly spinal injections of this drug for the rest of their lives or until other therapies like gene editing become available. Even after the phase three trial we will not know whether this drug will work in the long-term; there is much still to learn.

IONIS-HTTRX has made tangible progress towards treating Huntington’s disease, but it is not a panacea. It cannot reverse brain cell loss, it won’t be appropriate for everyone and young people with Juvenile HD are currently excluded from clinical trials. Our hope is that it can make HD a manageable long-term condition; that would be a long way from its current status as incurable and arguably one of the most devastating conditions known to humankind. Perhaps one of the greatest promises this drug offers is the diminution of the fear and stigma that still cloaks Huntington’s disease and which does almost as much harm is the condition itself.

John Eden, Chief Executive, Scottish Huntington’s Association