FIELD: pharmaceutical industry.SUBSTANCE: invention refers to an agent inducing in vivo in vivo replacement of tumor tissue connective and transferring tumor cells from G1 phase of cell cycle into rest state G0. In vivo infertility agent substituting connective tumor tissue and transferring tumor cells from G1 phase of cell cycle to rest state G0, which is a dry extract of Gratiola officinalis leaves obtained by milling them, extraction with 96 % alcohol in a water bath until boiling and boiling for 14–15 minutes, evaporation at temperature of 55–60 °C, diluting the evaporated residue first with distilled water at temperature of 40–50 °C, then adding chloroform in proportion of 4/5 of water and 1/5 of the chloroform, cooling to room temperature and centrifugation at 1500 rpm for 15 minutes, followed by separation of the aqueous fraction and drying it.EFFECT: above described agent is effective for in vivo substitution of tumor tissue connective and for transfer of tumor cells from G1 phase of cell cycle into rest state G0.1 cl, 8 dwg, 3 tbl, 2 ex