Pyrimethamine

Pyrimethamine is an antiprotozoal agent that is primarily active against P. falciparum, inhibiting the protozoal enzyme dihydrofolate reductase (DHFR).¹ By blocking DHFR activity, pyrimethamine prevents the production of tetrahydrofolic acid, an essential coenzyme involved in DNA and RNA synthesis. In in vivo antimalarial mouse models, pyrimethamine displays a prophylactic effect at an ED₅₀ value of 0.5 mg/kg.² Sulphonamides act synergistically with pyrimethamine by arresting production of dihydrofolic acid, resulting in the sequential blockade of the folate pathway of protozoa.³ Pyrimethamine has also been found to limit the expression of the superoxide dismutase 1 (SOD1) gene, a metalloenzyme involved in amyotrophic lateral sclerosis.⁴

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1. Peters, W. Chemoprophylaxis and chemotherapy. Brit. Med. J. 2, 95-98 (1971).

2. Adebajo, A.C., Odediran, S.A., Aliyu, F.A., et al. In vivo antiplasmodial potentials of the combinations of four nigerian antimalarial plants. Molecules 19(9), 13136-13146 (2014).

3. Hwang, J., Bitarakwate, E., Pai, M., et al. Chloroquine or amodiaquine combined with sulfadoxine-pyrimethamine for uncomplicated malaria: A systematic review. Trop. Med. Int. Health 11(6), 789-799 (2006).

4. Limpert, A.S., Mattmann, M.E., and Cosford, N.D.P. Recent progress in the discovery of small molecules for the treatment of amyotrophic lateral sclerosis (ALS). Beilstein J. Org. Chem. 9, 717-732 (2013).