18F-thymidine + pemetrexed

This is a combination of two agents used in oncology research and clinical trials: - **18F-thymidine (also known as 3'-deoxy-3'-[18F]-fluorothymidine or FLT)** is a radiolabeled thymidine analog used as an investigational PET imaging tracer. It serves as a marker for cellular proliferation by being taken up via the thymidine salvage pathway and phosphorylated by thymidine kinase 1 (TK1), but it is not incorporated into DNA. Its uptake increases transiently ("flare") after inhibition of de novo thymidylate synthesis. - **Pemetrexed** is an approved small molecule antifolate chemotherapeutic agent that inhibits several folate-dependent enzymes involved in nucleotide synthesis, most notably thymidylate synthase (TS), dihydrofolate reductase (DHFR), and glycinamide ribonucleotide formyltransferase (GARFT). This leads to inhibition of DNA synthesis and cell death in rapidly dividing tumor cells. The combination is not a therapeutic regimen but rather refers to the use of FLT-PET imaging to monitor early pharmacodynamic effects or response to pemetrexed therapy—particularly TS inhibition—in patients with non-small cell lung cancer (NSCLC). The "FLT flare" phenomenon observed on PET scans after administration of pemetrexed reflects activation of the thymidine salvage pathway due to TS blockade[1][2][5].

Other names

3'-deoxy-3'-[18F]-fluorothymidine + pemetrexedFLT + pemetrexed