Aubagio (teriflunomide), an approved medicine for relapsing forms of multiple sclerosis (MS), specifically targets highly metabolic and more autoreactive T-cells, analysis of the Phase 3 TERI-DYNAMIC clinical trial data shows.
The findings, contrary to expectations, support a selective effect of Aubagio on different T-cell populations.
The study “Teriflunomide treatment for multiple sclerosis modulates T cell mitochondrial respiration with affinity-dependent effects” was published in the Science Translational Medicine journal.
In MS, immune cells, or lymphocytes known as T-cells, attack and destroy myelin, the fat-rich substance that wraps around nerve fibers (axons). Myelin loss creates lesions that affect nerves of the brain and spinal cord.
Previous evidence suggested that T-cells, depending on their active or resting state, rely on specific ways of energy production or metabolism.
Aubagio, marketed by Sanofi Genzyme, is a well-known inhibitor of a mitochondrial enzyme called dihydroorotate dehydrogenase (DHODH), that is crucial for the activity of T-cells. However, how Aubagio selectively targets the autoreactive T-cells is poorly understood.
To shed light on this matter, an international group of researchers used data from the TERI-DYNAMIC clinical trial that tested Aubagio in patients with relapsing form of MS to better understand how the therapy inhibited the patients’ self-immune responses.
The Phase 3, open-label TERI-DYNAMIC trial (NCT01863888) included 70 patients from Belgium, Germany, and The Netherlands, aged 18 to 56. Participants received Aubagio as a 14 milligram (mg) once-daily, oral dose, and researchers assessed the changes in immune cells’ profile up to 24 weeks.
Results showed that, contrary to what was expected, Aubagio was not generally decreasing T-cell levels in treated patients. Instead, it significantly reduced a particular subset of T-cells, called “Th1 helper cells.”
Moreover, researchers found that the diversity of T-cell receptors — the surface proteins that can recognize a particular antigen (a protein that can elicit an immune response) — making T-cells specific to a certain target was reduced in MS patients after treatment with Aubagio.
These findings suggested that some T-cells were particularly susceptible to Aubagio.
Using a mouse model for MS, the experimental autoimmune encephalomyelitis (EAE) model, researchers showed that the CD4+ T-cells (helper T-cells) and CD8+ T-cells, those that reacted most strongly against self-antigens, were the most sensitive to DHODH inhibition by Aubagio.
Moreover, researchers saw that Aubagio was not affecting the production of pro-inflammatory molecules — called cytokines — at the cell level, but their overall decrease probably was due to the reduction in T-cell numbers.
In line with these findings, CD4+ T-cells that produced the cytokine interferon gamma were significantly reduced with Aubagio treatment, whereas CD4+ T-cells that produced interleukin 17A were unchanged. This suggests that Aubagio is able to interfere with specific sub-types of immune cells.
When the team compared the metabolic profile of T-cells from healthy subjects with that from patients with relapsing-remitting MS (RRMS) in both remission and in relapse phases, they found that the metabolism of T-cells from the last group was significantly altered, and thus targetable.
Altogether, the results suggested that T-cells with a high-affinity to self-antigens are more susceptible to inhibition of the DHODH enzyme by Aubagio.
“Therapeutic targeting of metabolic alterations might represent an attractive concept in MS, and might represent an as yet unrecognized key mechanism of teriflunomide-mediated immune modulation in this disease,” the researchers concluded.