Wof is a disease modifying antirheumatic drug whose active metabolite inhibits the enzyme dihydro-orotate dehydrogenase
**Core Concept**
Wof is a disease-modifying antirheumatic drug (DMARD) that targets the synthesis of pyrimidine nucleotides, which are essential for the proliferation of T and B lymphocytes. The inhibition of dihydro-orotate dehydrogenase (DHODH) is a crucial step in this pathway, as it prevents the conversion of dihydroorotate to orotate.
**Why the Correct Answer is Right**
The active metabolite of Wof, leflunomide, is responsible for inhibiting DHODH. This enzyme is a mitochondrial flavoprotein that catalyzes the oxidation of dihydroorotate to orotate in the de novo pyrimidine synthesis pathway. By inhibiting DHODH, leflunomide reduces the proliferation of T and B lymphocytes, which are key players in the pathogenesis of rheumatoid arthritis. The inhibition of DHODH also leads to a decrease in the levels of pyrimidine nucleotides, which are essential for the synthesis of DNA and RNA.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct mechanism of action of Wof. While Wof is a DMARD, its mechanism of action is not solely through the inhibition of dihydro-orotate dehydrogenase.
**Option B:** This option is incorrect because it is a general statement about DMARDs, but it does not specifically address the mechanism of action of Wof.
**Option C:** This option is incorrect because it is not a correct description of the mechanism of action of Wof.
**Clinical Pearl / High-Yield Fact**
It's essential to note that Wof is a prodrug, meaning that it requires metabolic activation to become effective. The active metabolite, leflunomide, is responsible for the therapeutic effects of Wof.
**Correct Answer:** C. Leflunomide