A drug called vorasidenib (also known as Voranigo) is being assessed for use on the NHS as a new treatment for low-grade glioma.
Vorasidenib can be used to treat adults and children aged 12 years and older, with grade 2 astrocytoma or oligodendroglioma with a susceptible isocitrate dehydrogenase mutation (IDH1 or IDH2).
What is low-grade glioma?
A glioma is a type of brain tumour that develops from glial cells – support cells which are essential in the maintenance and function of the central nervous system. Gliomas are classified in four grades, with grade 1 and grade 2 being known as low-grade gliomas.
Usually occurring in children and teenagers, grade 1 gliomas are the most slow-growing form and carry the longest prognosis. Grade 2 gliomas are more common in adults but can also occur in children and teenagers. They are initially slow-growing but often progress to a higher grade through time – usually over years. The tumours can also be diffuse, which means they have no clear edge and invade nearby brain areas, making treatment more difficult.
Treatment can include surgery and for some patients, radiotherapy and chemotherapy.
What is vorasidenib?
Vorasidenib is the first targeted systemic therapy approved for IDH-mutant low-grade glioma.
How does it work?
IDH1 and IDH2 are a group of enzymes which play an important role in cell metabolism.
Mutations of IDH1 and IDH2 are present in nearly all grade 2 diffuse gliomas in adults. These mutations lead to the production of a chemical compound called d-2-hydroxyglutarate. Elevated levels of d-2-hydroxyglutarate disrupt how cells develop and contribute development of a tumour.
Vorasidenib inhibits (or blocks) mutant IDH1 and IDH2 enzymes. This reduces levels of d-2-hydroxyglutarate, helping to stop or slow tumour growth.
The drug could be offered to patients who have undergone surgery, but who are not in need of immediate radiotherapy and chemotherapy. Crucially, unlike many other drugs which target IDH mutations, vorasidenib is able to cross the blood-brain barrier.
Why is stalling or slowing tumour growth important?
Diffuse gliomas with IDH mutation are the most common aggressive primary brain tumours diagnosed in adults younger than 50 years of age, with the majority of people diagnosed in their 20s, 30s or 40s.
The majority of these tumours are not curable with current treatments and continue to grow and infiltrate normal brain tissue when left untreated.
The current standard of care for patients is surgery, radiation and chemotherapy; however, many patients may be monitored through a ‘watch and wait’ approach as the treatments themselves can cause harsh side effects significantly impacting quality of life.
Vorasidenib has been shown to extend progression-free survival, lengthening the period of time for which patients could go without needing radiotherapy or chemo, thus delaying the harsh side effects caused by these treatments.
How was vorasidenib shown to be effective?
An international phase 3 clinical trial showed the targeted therapy more than doubled progression-free survival in people with recurrent grade 2 glioma.
Compared with people who received a placebo, those who took vorasidenib went for nearly 17 additional months without their cancer worsening. Patients who took the drug did not need further intervention (chemotherapy and radiation) until much later.
You can read more about the INDIGO trial here.
More research is needed to understand whether vorasidenib could extend life expectancy for patients with IDH-mutant gliomas.
Is vorasidenib available on the NHS?
No – vorasidenib is not currently available on the NHS.
What are the next stages?
Vorasidenib was licensed by the MHRA in September 2025. This means the drug has been deemed safe, of high-quality and effective, and allows it to be legally sold, supplied and privately prescribed in the UK. It is worth noting that although a medication is deemed safe by the MHRA, this does not mean that it is free from side effects.
The next step is for the drug to be appraised by NICE. This process assesses the clinical and cost-effectiveness for NHS use, considering factors like health benefit, treatment cost and value for money.
Expert comment
Reacting to the results of the INDIGO clinical trial, Dr Garth Cruikshank, Emeritus Professor of Neurosurgery and Clinical Advisor to the Charity, said: “The INDIGO trial has provided a highly convincing, highly promising and somewhat surprising result.
“Highly convincing, because it has been performed as a double blinded controlled trial in highly comparable test and control arms with more than adequate numbers of patients.
“Highly promising in that there is significant prolongation of progression-free survival and delay in time-to-next-intervention with a very manageable safety profile. This latter issue being very important bearing in mind patients would have to take this drug for an extended period.
“Surprising because, although we understand that the mutant enzymes were inhibited resulting in a suppression of the production of oncogenic stimulator 2-HG, it is the first targeted therapy to show activity in glioma in more than a very limited number of patients.
“This study is a game changer for our insight into gliomagenesis, but also for all patients who present with IDH mutated glioma, offering significant survival improvement at low cost to their quality of life, and the postponement of damaging radiotherapy. It heralds a new era for these patients”