Potential Anti-Tumor Drug: Co-Crystal 5‑Fluorouracil-nicotinamide

5-Fluorouracil-nicotinamide (5-FU-NCM), a co-crystal with a 2D layer structure formed by hydrogen bonds, was synthesized by solvent evaporation and liquid phase-assisted grinding at room temperature. Compared to 5-FU alone, the results of solubility, oil–water partition coefficient, anti-tumor effect in vivo and vitro, acute toxicity, and pharmacokinetic parameters indicate that the co-crystal is a potential anti-tumor drug.