[A novel immunoregulating hexapeptide with antineoplastic effect].

A synthesized analog of myelopeptide HP-2-->M[symbol: see text]-2 (Leu-Val-Val-Tyr-Pro-Trp) caused a significant (60-80%) and prolonged inhibition of s.c. grafted tumors P388, Ca-755, B-16 and sarcoma 180 in isogenic mice but did not affect the growth of tumor B-16 in nude mice. Nor did it influence proliferative activity or viability of cultured human tumor cells. The best results were obtained with s.c. injections of 0.5-2 mg/kg HP-2-->M[symbol: see text]-2, twice or trice a day, at 96 hr intervals. No symptoms of severe poisoning were registered at doses of HP-2-->M[symbol: see text]-2 100 times the therapeutic one. A pharmacokinetic study in mice revealed prolonged circulation of HP-2-->M[symbol: see text]-2 in blood and a high affinity for the bone marrow (t 1/2 (130.1 hr and 431.6 hr, respectively). HP-2-->M[symbol: see text]-2 restored in vitro the ascites P388-suppressed cytotoxicity of murine T-lymphocytes. HP-2-->M[symbol: see text]-2 is regarded as a candidate for clinical studies of its potential of immunocorrection in cancer patients suffering T-lymphocyte immunity disturbances.