The effect of release-active antibodies to TNF-α (Artrofoon) on the development of Walker carcinosarcoma 256 was studied in Wistar rats. Intragastric dose of this drug significantly inhibited the growth of tumor node (55% inhibition of tumor growth), but less effectively than the reference drug cyclophosphamide (80%). The studied drug significantly prolonged animal' lifespan (+97%) and its efficiency in this respect was comparable to that of cyclophosphamide (+96%).