A disease-modifying drug that targets the root of the disease
Leflunomide belongs to the family of disease-modifying antirheumatic drugs, known by the acronym DMARD.
Unlike simple anti-inflammatories, it does not act on symptoms alone: it targets the immune mechanism driving the disease and can slow the progression of joint damage. Its main use is in rheumatoid arthritis.
An industrial origin and a prodrug status
Leflunomide is a synthetic molecule derived from an isoxazole ring. It was developed by the Hoechst laboratories, later renamed Aventis, and was approved in 1998.
It is a prodrug: administered in an inactive form, it is converted inside the body into its active metabolite, teriflunomide, which carries the therapeutic effect. This metabolite later went on to have a career of its own, becoming a standalone medicine used in multiple sclerosis.
From inactive molecule to active metabolite
Leflunomide's structure is built around an isoxazole ring. After absorption, this ring opens to release teriflunomide, the molecule's truly active form.
Leflunomide is produced by chemical synthesis and administered orally, in tablet form.
A mechanism of action that targets immune cell proliferation
The active metabolite inhibits a key enzyme, dihydroorotate dehydrogenase (DHODH), which is essential for the de novo synthesis of pyrimidines, the building blocks of DNA and RNA.
By depriving activated lymphocytes of the nucleotides they need to multiply, leflunomide slows the proliferation of the immune cells responsible for joint inflammation. The result is a disease-modifying immunomodulatory and anti-inflammatory effect.
Its very long presence in the body, spanning several weeks, is due to a recirculation cycle through the liver and intestine.
Indications and precautions
Leflunomide is mainly indicated for active rheumatoid arthritis in adults and for active psoriatic arthritis.
Its use requires monitoring of liver function, blood cell counts, and blood pressure. It is contraindicated during pregnancy due to a teratogenic effect.
Because of its long persistence in the body, an accelerated elimination procedure, known as a "wash-out," using cholestyramine or activated charcoal, may be necessary.