Gimeracil(Gimestat) is an inhibitor of dihydropyrimidine dehydrogenase (DPYD), which degrades pyrimidine including 5-fluorouracil in the blood; inhibits homologous recombination.IC50 Value: Target: DPYDin vitro: Gimeracil had radiosensitizing effects by partially inhibiting homologous recombination (HR) in the repair of DNA double strand breaks. Tail moments in neutral comet assay increased in gimeracil-treated cells. Gimeracil restrained the formation of foci of Rad51 and replication protein A (RPA), whereas it increased the number of foci of Nbs1, Mre11, Rad50, and FancD2. Gimeracil did not sensitize DPYD-depleted cells [1]. Gimeracil inhibited DNA DSB repair. It did not sensitize cells deficient in HR but sensitized those deficient in NHEJ. In SCneo assay, Gimeracil reduced the frequency of neo-positive clones. Additionally, it sensitized the cells in S-phase more than in G0/G1 [2].in vivo:

References:
[1]. Sakata K, et al. Gimeracil, an inhibitor of dihydropyrimidine dehydrogenase, inhibits the early step in homologous recombination. Cancer Sci. 2011 Sep;102(9):1712-6.
[2]. Takagi M, et al. Gimeracil sensitizes cells to radiation via inhibition of homologous recombination. Radiother Oncol. 2010 Aug;96(2):259-66.