Abstract: The disclosure provides a method of new use of an immunomodulatory drug comprising a water-soluble acidic peptidoglycan from sprouts of the plant Solanum tuberosum (WSPG) for prevention and treatment of metastatic tumor growth, comprising an application of a therapeutically effective dose of a said immunomodulatory drug or a pharmaceutical composition of a said immunomodulatory drug with a pharmaceutically acceptable carrier or excipient, or a pharmaceutically effective amount of mammalian immune cells treated with said immunomodulatory drug WSPG in vitro/ex vivo to a patient in need thereof.