Triazolo- and tetrazolopyridazine derivatives and their hypotension and heart rate activity.

6-Chloro-, 6-morpholino- and 6-N-methylpiperazino-1,2,4-triazolo[4,3-b]- or 1,2,3,4-tetrazolo[1,5-b]pyridazines [II-VII] were synthesized from 3-chloro-6-hydrazinopyridazine [I]. Positive effect of a series of tetra- and triazolopyridazines for lowering blood-pressure without affecting the heart rate was found in tests on rats. Their lipophilicity and other properties are discussed.

Experimental antitumor activity of new azathioprine analogues.

Two newly synthesized azathioprine (AZA) analogues, 6-(1,2-dimethyl-4-nitro-5-imidazolyl)thiopurine (Met-AZA) and 6-(2-methyl-5-nitro-4-imidazolyl)thiopurine (IZO-AZA), were investigated against KB human tumor cells. In 5 transplantable murine tumor models, including sc Sa180, sc Ca755, ip LL and ip leukemias; L1210 and P388 both drugs were found to be antitumor active in all the experiments carried out regardless of dosing regimen or the route of administration. Similar good activity was shown in the KB, ip Sa180, and Ca755 systems and partly against LL as compared to AZA.

Cytostatic activity of pyridazinee derivatives. Part III. Cytotoxic studies on some pyridazine-3,6-diones and pyridazin-6-ones using a particle counter and a proliferation inhibition test.

The cytoxicity of 10 pyridazine-3,6-dione and 11 pyridazine-6-one derivatives was studied on L-1210 cells using the proliferation inhibition (PI) test and particle counter (PC) test. Eight compounds with ED50 value below 1 microgram/ml in the PI system and with minimal effective concentration (MEC) below 0.2 mg/ml in the PC system, were qualified for further in vivo investigation.

Cytostatic activity of pyridazine derivatives. Part II. In vitro studies on halogen derivatives of 6-pyridazinone and 3,6-pyridazinedione.

Cytotoxicity f 22 halogen derivatives of 6-pyridazinone (6-PD-ones) and 2-methyl-3,6-pyridazinedione (3,6-PD-diones) was studied on KB and HeLa human tumor tissue cultures. 15 compounds with ED50 activity values ranging between 0.043-2.

Cytostatic activity of pyridazine derivatives. I. In vitro studies on 1-methoxyphenylpyridazine-6-ones.

Cytotoxicity of 15 pyridazine derivatives was studied by tissue method on human KB and HeLA cell lines. Six compounds with ED50 activity values between 0.025 and 1.