The efficacy of bleomycetin or bleomycin A5 was studied in 128 patients with different malignant neoplasms. The antibiotic was used as a systemic or intracavitary chemotherapeutic agent. Bleomycetin was effective in 75-80, 81.8, 58.3, 70 and 50 per cent of the cases with disseminated derminogenic tumor of the testicle, squamous cell carcinoma of the head and neck, cancer of the penis, carcinoma of the skin and lymphogranulomatosis, respectively. When used intracavitarily the drug was effective in 41.2 per cent of the patients with cancer of the ovaries and lungs, teratoblastoma of the ovaries, cancer of the mammary gland and sarcoma of the soft tissues. Hyperthermia and focal hyperkeratosis as the adverse reactions were observed in 40.6 and 5.4 per cent of the patients, respectively. No toxicity with respect to the lungs was registered.

A study was made of antitumor and toxic properties of retinoid C15 which has some characteristic structural features of retinoic acid natural metabolites; such as ethyl-2E, 4E-3-methyl-5-/2,6-dimethyl-6-ethoxycarbonyl-/3-oxo-1-cyclohexene-1-yl/-2,4-pentadienoate. The substance inhibited the growth of transplantable tumors of the uterine cervix. Lewis carcinoma and rumen cancer. This ability was dependent on the tumor growth rate. The substance proved less toxic then retinoic acid or methyl retionate. Injection of retinoid C15 was accompanied by the widening of the paracortical zone of the mesenterial lymph node and by the increased number of lymphoid follicles in the spleen.

The composition of virenomycin, a new antitumor antibiotic was studied. Two components V and M were detected with high resolution liquid chromatography and thin layer chromatography on siluphol (Czechoslovakia) and silica gel (Merk, BRD). A preparative method for separation of the antibiotic components with the use of chromatography on columns with silica gel was developed. Biological and physicochemical properties of separate components were studied to show that they significantly differed by their antibacterial action in vitro: virenomycin V was 2 to 4 times more active than virenomycin M against a number of microbes. The physicochemical properties of the components are similar. It was shown with mass spectrometry that the molecular weight of virenomycin is 12 units higher than that of virenomycin M. The PMR spectra showed that this difference is due to the presence of a vinyl group in the chromophore moiety of the virenomycin V molecule and a methyl group at the similar site of the virenomycin M molecule.

Significant changes in the nucleus structure, complete suppression of the mitotic activity, markedly decreased synthesis of RNA (by 70--80 per cent according to incorporation of 3H-uridine) and decreased levels of DNA (by 40 per cent according to olivomycin binding) were observed in the fibroblasts cultivated in vitro due to exposure to actinoxanthine in an amount of 50 microgram/ml. The data indicate direct damaging effect of the drug on the cell chromatin. The above nuclear changes were also observed after a short-term exposure of the cells to the drug (up to 5 minutes). Still, they became evident only after the subsequent incubation of the cells in a pure culture medium for at least 15 minutes. No such changes in the nucleus structure were detected when after the 5-minute exposure to actinoxanthine the cells were exposed to trypsin for 3 minutes. When the time of exposure to actinoxanthine was longer (15 minutes and higher), trypsin suppressed the manifestation of the above nuclear changes. The two-stage mechanism of the damaging effect of actinoxanthine on the chromatin of the cells cultivated in vitro is discussed. The damaging effect of actinoxanthine on the cells begins from binding of the drug with the cell membrane. After that a short incubation period follows and then the characteristic changes in the nucleus structure appear.