Hydroxyurea is used in sickle cell disease to raise fetal hemoglobin. Its primary molecular target in nucleotide metabolism is:

• A Carbamoyl phosphate synthetase II, blocking pyrimidine ring assembly
• B Thymidylate synthase, blocking conversion of dUMP to dTMP
• C Dihydrofolate reductase, blocking regeneration of tetrahydrofolate
• D Ribonucleotide reductase, blocking conversion of NDPs to dNDPs ✓

Explanation

Hydroxyurea destroys the tyrosyl free radical of ribonucleotide reductase, the enzyme that reduces ribonucleoside diphosphates to deoxyribonucleoside diphosphates for DNA synthesis. It therefore arrests cells in S phase. Methotrexate targets DHFR and 5-fluorouracil targets thymidylate synthase, while no standard antineoplastic targets CPS II. Stress erythropoiesis induced by hydroxyurea also shifts hemoglobin production toward HbF.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.