5-Fluorouracil, an anti-metabolite used in cancer treatment, is activated to:
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- 5-Fluorouracil is converted to 5-fluoro-2-deoxyuridylic acid (FdUMP), which inhibits thymidylate synthase and blocks DNA synthesis.
- FdUMP is responsible for the drug’s action in chemotherapy, specifically targeting rapidly dividing cancer cells.
- 5-fluoro-2-oxyuridylic acid
- 3-fluoro-3-deoxyuridylic acid
- 3-fluoro-3-oxyuridylic acid
- 5-fluoro-2-deoxyuridylic acid
The Correct Option is D
Approach Solution - 1
5-Fluorouracil (5-FU) is a chemotherapy drug that works by inhibiting the synthesis of thymidylate, a critical nucleotide required for DNA replication. Upon administration, 5-fluorouracil is metabolized and activated in the body to form 5-fluoro-2-deoxyuridylic acid (FdUMP), which is the active form of the drug. FdUMP works by binding to the enzyme thymidylate synthase, thereby inhibiting the conversion of deoxyuridine monophosphate (dUMP) to thymidine monophosphate (dTMP), an essential building block for DNA synthesis. This inhibition causes DNA replication to stop, leading to cancer cell death.
Why Other Options Are Incorrect:
- (A) 5-fluoro-2-oxyuridylic acid: This compound does not represent the activated form of 5-fluorouracil.
- (B) 3-fluoro-3-deoxyuridylic acid: This is not the correct metabolite of 5-fluorouracil.
- (C) 3-fluoro-3-oxyuridylic acid: This is also not the correct product after activation of 5-fluorouracil.
Thus, the correct activated form of 5-fluorouracil is 5-fluoro-2-deoxyuridylic acid (FdUMP).
Approach Solution -2
The question asks for the specific activated metabolite that 5-fluorouracil is converted into inside the body. Let's examine the naming in each option.
- 5-fluoro-2-oxyuridylic acid: This name uses an 'oxy' designation at the 2-position rather than 'deoxy', which does not correctly describe the sugar modification present in the true active metabolite of 5-fluorouracil.
- 3-fluoro-3-deoxyuridylic acid: The fluorine substitution in 5-fluorouracil sits at the 5-position of the uracil ring, not the 3-position, so a name locating the fluorine at position 3 does not match the actual structure of the drug's active form.
- 3-fluoro-3-oxyuridylic acid: This option carries both a wrong ring position for the fluorine (3 instead of 5) and a wrong sugar descriptor (oxy instead of deoxy), so it does not correspond to the real metabolite either.
- 5-fluoro-2-deoxyuridylic acid: Inside the cell, 5-fluorouracil is converted through the pyrimidine salvage pathway into 5-fluoro-2-deoxyuridine-5-monophosphate (FdUMP). This name correctly places the fluorine at the 5-position of the uracil ring and correctly identifies the sugar as a 2-deoxyribose, matching FdUMP exactly. FdUMP is the species that binds to and blocks thymidylate synthase, the enzyme that normally converts dUMP to dTMP, so its formation halts DNA synthesis in rapidly dividing cancer cells.
Only the fourth option correctly places both the position of the fluorine substitution and the deoxy sugar modification that together define the true active metabolite.
Therefore, the correct answer is 5-fluoro-2-deoxyuridylic acid.
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