Preclinical studies were performed in mice, rats and dogs of cis-diamminedichloroplatinum(II) (CDDP) and its derivatives cis-1,1-di(aminomethyl) cyclohexane platinum(II) sulphate (TNO-6), ...cis-diammine-1,1-cyclobutanedicarboxylate platinum(II) (CBDCA) and cis-dichloro, trans-dihydroxybis-isopropylamine platinum(IV) (CHIP). In mice toxicity and antitumour activity were determined. All three derivatives were at least as toxic as CDDP for haemopoietic stem cells and were less active than CDDP against the mouse tumours leukaemia L1210 and osteosarcoma C22LR. Toxicology studies in rats revealed no renal toxicity after a single dose of TNO-6. Fractionated doses of TNO-6 and CBDCA did cause renal toxicity but less than CDDP. CHIP produced little or no kidney damage. In dogs, TNO-6 (1.5 mg/kg) produced more severe kidney damage--although this was reversible--than CDDP (2 mg/kg). Half-lives of distribution were 4.0-5.1 min for TNO-6 and 9.7 min for CDDP, while half-lives of elimination were 3.6-6.6 days and 5.9 days respectively. Plasma levels, normalized for the dose, were at least two times higher after TNO-6 than after CDDP. Twelve weeks after drug administration, plasma levels were undetectable, while tissue concentrations could still be measured. The platinum concentration in kidney cortex was higher after CDDP than after TNO-6.
In collaborative experiments the CFU survival in mouse bone-marrow has been investigated after in vivo irradiation with D-T neutrons, 300 kV x-rays and
60
Co and
137
Cs gamma-rays. All the survival ...curves for x- and gamma-radiation showed the same extrapolation number (2·47 ± 0·28), whereas D
0
values of 72·2 ± 1·7 rads and 90·7 ± 2·4 rads, respectively, were found for the two types of radiation. With D-T neutrons, the Manchester group found a D
0
value of 62·5 ± 2·2 rads; the Rijswijk group found a D
0
value of 78·3 ± 2·1 rads. A common extrapolation number of 1·34 ± 0·16 could be calculated for the neutron survival curves. Owing to the difference in extrapolation numbers for x-rays and neutrons, the RBE depends on the level of survival. From the combined results of both groups a mean RBE of 1·1 can be derived for low surviving fractions.
The 25 per cent difference in the effectiveness of D-T neutrons, as measured by the two groups, was not due to dose-rate nor to the strain of mice, and could only in part be attributed to the 8 per cent difference in dosimetry revealed by intercomparative measurements. It was probably due mainly to a difference in quality of the two neutron beams resulting from the collimation of the Manchester beam with consequent degradation of neutron energy.
Preclinical studies on toxicology and pharmacokinetics were performed for (1,1-bis(aminomethyl)cyclohexane)oxalatoplatinum(II) (TNO-38) in rats and a dog after LD10 and LD50 assessment in mice. In ...drug-treated rats, ura and creatinine concentrations were 1.4-1.9 times those in control rats. Histopathology showed necrosis of tubular epithelium of the kidneys, which was comparable to damage observed after treatment with cisplatin (CDDP), and extensive necrosis of crypt epithelium, especially in the ileum. Similar to CDDP, TNO-38 was emetic in the dog. Non-specific subacute inflammatory changes were observed in the ileum. Renal damage was much less pronounced. Half-lives of distribution and elimination were 6.2 min and 5.2 days, respectively. The cumulative excretion of Pt in urine over 1 and 7 days after drug treatment was 38.3 and 49.3% of the dose, respectively. Twelve weeks after drug administration, Pt concentrations were highest in kidneys and liver. TNO-38 is adequately water soluble. Its reported antitumour activity is consistently lower than that of CDDP. The drug's toxicity was, in general, comparable to that of CDDP. Its pharmacokinetic profile was very similar to that of CDDP. It is concluded that TNO-38 should probably not be further evaluated in clinical studies.
Spontaneous metastases in lymph nodes and/or the lung were obtained after tumour cell inoculation of four mouse tumours and one rat tumour into the foot-pads of syngeneic animals or their F1 hybrids. ...Following local radiotherapy with doses of 45-80 Gy, significantly more mice died with metastases than following local amputation of the tumour-bearing foot when the 2661 carcinoma was involved. No significant difference was observed after these treatments for the other tumours. The enhancement of metastastic growth after local radiotherapy in the 2661 carcinoma seems not to be due to incomplete killing of tumour cells in the foot. The presence of irradiated normal structures and tumour tissue after radiotherapy promoted the outgrowth of 261 carcinoma cells which were outside the radiation field at the time of treatment. Evidently, even under similar experimental conditions, radiotherapy may enhance the growth of metastases from some tumours and not from others.
Fourteen derivatives of sparsomycin (1) were synthesized. Six of them were prepared following a novel synthetic route starting from the L-amino acid alanine. Some physicochemical properties, viz. ...lipophilicity and water solubility, of selected derivatives were measured. The biological activity was tested in vitro in cell-free protein synthesis inhibition assays, in bacterial and tumor cell growth inhibition assays, and in the L1210 leukemia in vivo model in mice. Also for selected drugs the acute toxicity in mice was determined. Ribosomes from both an eukaryotic and a prokaryotic organism were used in the protein synthesis inhibition systems. A linear correlation between the lipophilicity parameters measured was observed. Water solubility and drug toxicity in mice were found to be linearly correlated with lipophilicity. All the derivatives studied are more lipophilic than 1. The deshydroxysparsomycin analogues (30-33) showed an interesting phenomenon: increase in hydrophobicity was accompanied by a considerable increase in water solubility. We found that an increase in hydrophobicity of the drug as a result of replacing the SMe group of 1 with larger alkylthio groups causes an increase in the biological activity of the drug. However, not only the hydrophobicity but also shape and size of the substituent are important; in the homologous series 1-9-10-11-12, 21-22-23-24, and 30-31-32-33, highest protein synthesis inhibitory and in vitro cytostatic activity is found with compounds 11, 23, and 32, respectively, and in comparison with the highly active n-butyl compound 10, the isomeric tert-butyl compound 13 is rather inactive. Polar substituents replacing the SMe group, i.e. Cl in 17 and 35, also render the molecule inactive. Substituting the bivalent sulfur atom for a methylene group decreases the drug's activity. This effect can be compensated for by increasing the length of the alkylsulfinyl side chain. The agreement between the results derived from cell-free and "in vivo" tests is good. The assays using ribosomes of bacterial and eukaryotic organisms give similar results although the latter seem to be more sensitive to changes in hydrophobicity of the drug. Our results confirm the presence of a hydrophobic region at the peptidyl transferase center of the ribosome; the interaction of sparsomycin with this region is more pronounced in the eukaryotic particles. The sparsomycin analogues 11, 23, and 30 show the highest antitumor activity against L1210 leukemia in mice, their median T/C values are 386, 330, and 216%, respectively.
