Cladribine is a selective immunosuppressant. It is a nucleoside analogue of deoxyadenosine (a DNA component) which acts on B and T lymphocytes causing lymphocyte death and interrupting the cascade of immune events central to MS.¹¹

Dimethyl fumarate activates a DNA transcriptional pathway, upregulating antioxidant genes and dampening down inflammation. Diroximel fumarate has similar activity which derives from both compounds’ main metabolite, monomethyl fumarate, with significantly reduced immune cell activation and a subsequent release of pro-inflammatory cytokines in response to inflammatory stimuli (cytokines are naturally occurring proteins with immunomodulatory, antiviral and antiproliferative properties). Monomethyl fumarate also affects lymphocyte phenotype production, down-regulating pro-inflammatory cytokine types and promoting anti-inflammatory types.¹¹

Fingolimod, ozanimod, ponesimod and siponimod are selective immunosuppressants. As sphingosine 1-phosphate (S1P) receptor modulators, they bind to specific subtypes of the S1P receptor on lymphocytes. The compounds stop lymphocytes from leaving lymph nodes and can stop pro-inflammatory cells from entering the CNS, where they would cause nerve inflammation and nerve tissue damage.¹¹

Teriflunomide is a dihydroorotate dehydrogenase (DHODH) inhibitor with immunomodulatory activity and anti-inflammatory properties. DHODH is an enzyme in cell mitochondria involved in pyrimidine biosynthesis. Inhibiting DHODH can reduce the proliferation of rapidly dividing cells that depend on pyrimidine to expand. Teriflunomide’s therapeutic effect in MS is not fully understood but is likely to be due to reducing lymphocyte numbers.¹¹