A new approach to the development of natural cancer drugs from hydrobionts selected for longevity and stress resistance is analyzed. The accelerated senescence program was successfully canceled in holarctic stickleback Gasterosteus aculeatus by crossing the marine and freshwater forms in ponds and selection of hybrids. Prolongation of fish life was accompanied by an increased production of the antistress exocrine secretion by the renal epithelium of male sticklebacks (glycoproteins, peptides, and mucoids), required for successful egg development. Trials of the biodrug prepared from this secretion on salmons with epithelioma, guinea pigs with affected skin, and mice with transplantable tumors demonstrated a good therapeutic effect of the biologic.