Introduction: The drug Licopid® (GMDP, glucosaminylmuramyldipeptide) is intended for complex therapy of conditions accompanied by secondary immunodeficiencies. This drug belongs to the group of microbial immunomodulators of bacterial origin. The transparent mechanism of action of the active substance GMDP allows putting the drug Licopid® into the category of promising immunotherapy drugs that are in demand in the complex therapy of many diseases resistant to traditional treatment. The objective of this study was to investigate the carcinogenicity of GMDP (Licopid®) in chronic animal experiments. Materials and Methods: The study of the carcinogenic effects of GMDP was carried out in mice hybrids F1 CBAxC57BL6 and Wistar rats of both sexes with intragastric administration five days a week (Mon-Tue-Wed-Thu-Fri) for 18 months at doses of 0.186 mg/kg, 1.86 mg/kg and 6.13 mg/kg to mice and for 21 months at doses of 0.086 mg/kg, 0.86 mg/kg and 2.83 mg/kg to rats. Results and Discussion: The results of the clinical observation of the experimental animals in the course of the study demonstrated the absence of differences between mice and rats of the experimental and control groups. Conclusion: Intragastric administration of GMDP to male and female mice for 18 months and rats for 21 months at the studied doses did not lead to tumor formation in the experimental animals.