Selective pharmaceutical sensitization design based on amino acid metabolism: 5-fluorouracil-sarcosine cocrystal prepared by wet powder grinding method

Pharmaceutical cocrystal is an emerging strategy not only to improve physicochemical properties, but also to generate synergistic effects. In this work, a novel cocrystal composed by 5-fluorouracil (5-FU) and sarcosine (SAR) was successfully assembled by wet powder grinding method. The cocrystal was characterized by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and Raman spectra. The differences of ¹H NMR spectroscopy between 5-FU/SAR physical mixture (PM) and cocrystal hinted the existence of supramolecular interactions between 5-FU and SAR in solid and solution. Bioavailability of cocrystal was increased than 5-FU. Most importantly, the weak interactions between 5-FU and SAR in cocrystal solution induced the superior cellar inhibition activity on 4T1 and BEL-7402 cells compared than 5-FU and PM. Cocrystal can interfere with the stability of methionine cycle and tetrahydrofolate (FH₄) level through the SAR-Gly-Met pathway, enhance the inhibition of thymidylate synthase (TS) compared to 5-FU, thereby interfering with cell cycle and inducing cell apoptosis. The results provided the novel strategy to develop the cocrystal drugs using bioactive amino acids as precursors to enhance the efficacy.