Objective:To develop and synthesize a novel derivative of ethyl pyruvate,named TZC02,and investigate its radioprotective effects against ionizing radiation(IR)-induced intestinal injury in mice. Methods:Male C57BL/6J mice weighing(20±2)g in the survival experiment were randomly divided into five groups(n=10 in each):control group,IR group,IR+TZC02(50 mg/kg)group,IR+TZC02(100 mg/kg)group,and IR+TZC02(200 mg/kg)group.Mice's survival rates were monitored for 7 d.In other experiments,the male mice were randomly divided into three groups(n=5 per group):control group,IR group,and IR+TZC02(100 mg/kg)group.TZC02 was intragastrically administered 1 h before 12 Gy abdominal γ-ray irradiation(ABI)and 24 h,48 h after irradiation,respectively.Three days after IR exposure,small intestinal tissues were collected and the number of small intestinal crypts was determined using hematoxylin & eosin(H&E)staining.Immunohis-tochemical analysis was used to assess the regenerative capacity of the small intestine(SI)and radiation-induced damage,stemness markers or DNA repair surrogates,including Ki67,lysozyme,and villus.The expressions of histone H2AX phosphorylation(γH2AX)and caspase-3 were evaluated through immunofluorescence analyses.Additionally,in vitro cultured small intestinal organoids were employed to investigate the effects of TZC02 on SI regeneration after irradiation. Results:The administration of TZC02 significantly improved the 7 d-survival rate of mice exposed to 12 Gy ABI(P＜0.05).Compared to the IR group,TZC02 treatment attenuated the decrease of SI Ki67-positive cells[(59.60± 6.33)vs.(37.70±7.82),t=11.89,P＜0.0001)and Paneth cells[(9.90±1.37)vs.(5.50±1.71),t=6.02,P＜0.001)in five crypts,and reduced structural damage to the SI[villus height,(349.49±60.17)pm vs.(294.72± 40.09)pm;t=3.39;P＜0.05].TZC02 also significantly decreased the crypt apoptosis detected by caspase-3[(10.75±1.26)vs.(29.83±2.56),t=13.39,P＜0.0001)and DNA damage detected by gH2AX[(10.40± 1.14)vs.(29.60±2.70),t=10.13,P＜0.0001)].The organoid survival 7 d post-irradiation further confirmed the protective effects of TZC02(area of organoids,(0.119±0.081)mm2 vs.(0.080±0.037)mm2;t=2.30;P＜0.05). Conclusions:This study demonstrate that TZC02 can offer effective protection against IR-induced intestinal injury,suggesting its potential as a promising protective compound for patients treated with radiotherapy.