Structure-activity relationship of aniline mustards acting against B-16 melanoma in mice.

A set of 23 aniline mustards [X-C6H4N(CH2CH2Cl)2] have been tested for their activity against B-16 melanoma in mice. The following quantitative structure-activity relationship (QSAR) correlates the data well: log 1/C = -2.06 sigma - 0.15 pi - 0.13 pi2 + 4.13 (r = 0.936). When this equation is compared with those formulated for aniline mustards acting against leukemia, it is found that log P0 (ideal lipophilicity) is higher for solid tumors. The QSAR brings out the unique activity of phenylalanine aniline mustard.

Structure-activity relationships in antitumor aniline mustards.

Quantitative structure-activity relationships (QSAR) have been formulated for the hydrolysis of aniline mustards and their antitumor activity against Walker 256 tumor and L1210 and P388 leukemia. In general, the antitumor activity parallels hydrolysis under the conditions defined by Ross; toxicity (LD50) parallels antitumor efficacy. Chlorambucil is an exception. A most important finding is that ideal lipophilicity for effectiveness against Walker tumor appears to be much higher than for the leukemias which suggests that solid tumors may, in general, require more lipophilic drugs than leukemias.

Mutagenicity of substituted (o-phenylenediamine)platinum dichloride in the Ames test. A quantitative structure-activity analysis.

A set of 13 substituted (o-phenylenediamine)platinum dichlorides has been studied in the Ames test using Salmonella typhimurium (TA-92). These cis-platinum compounds are mutagenic without activation by microsomes. The following correlation equation shows that the most important determinant of mutagenicity by substituents (X) is electron withdrawal via through resonance: log 1/C = 2.23 sigma sigma minus + 5.78. C in this expression is the molar concentration of compound producing 30 mutations/10(8) bacteria initially delivered above background mutation, and sigma minus is the Hammett constant obtained from substituted anilines.

A comparison of mutagenic and carcinogenic activities of aniline mustards.

A set of 15 derivatives of aniline mustard (I) was tested to give a quantitative measure of mutagenicity in Salmonella typhimurium TA-1535 and TA-100 and also carcinogenicity as lung tumors in strain-A mice. The structural variation in the set was chosen to minimize collinearity between hydrophobic, electronic, and molar refractive properties. By these measures, there was not a direct relationship between mutagenicity and carcinogenicity; in fact, since the 4-OPh analogue ranked highest in mutagenicity and among the lowest in carcinogenicity, while the reverse was noted for the 3,5-(NHCONH2)2 analogue, an inverse relationship was marginally significant. S-9 activation was required in the Ames test using TA-100, and the dose-response curve, prior to toxicity, appeared biphasic.

Potential antitumor agents. 36. Quantitative relationships between experimental antitumor activity, toxicity, and structure for the general class of 9-anilinoacridine antitumor agents.

Quantitative relationships (QSAR) have been derived between antileukemic (L1210) activity and agent physicochemical properties for 509 tumor-active members of the general class of 9-anilinoacridines. One member of this class is the clinical agent m-AMSA (NSC 249992). Agent hydrophobicity proved a significant but not a dominant influence on in vivo potency. The electronic properties of substituent groups proved important, but the most significant effects on drug potency were shown by the steric influence of groups placed at various positions on the 9-anilinoacridine skeleton. The results are entirely consistent with the physiologically important step in the action of these compounds being their binding to double-stranded DNA by intercalation of the acridine chromophore between the base pairs and positioning of the anilino group in the minor groove, as previously suggested. An equation was also derived for the acute toxicities of 643 derivatives of 9-anilinoacridine. This equation took a somewhat similar form to the one modeling antileukemia potency, emphasizing the usual fairly close relationship between potency and acute toxicity for antitumor agents in general. This study demonstrated the power of QSAR techniques to structure very large amounts of biological data and to allow the extraction of useful information from them bearing on the possible site of action of the compounds concerned.

Arachidonic acid-dependent metabolism of (+/-)-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene to polyguanylic acid-binding derivatives.

Microsomal and solubilized enzyme preparations from ram seminal vesicles catalyze the oxidation of (+/-)-7,8-dihydroxy-7,8-dihydrobenzo[alpha]-pyrene (BP-7,8-diol) to derivatives which covalently bind to polyguanylic acid (poly(G)). Oxidation requires prostaglandin endoperoxide synthetase and its substrate arachidonic acid and is inhibited by indomethacin. High performance liquid chromatographic (HPLC) analysis of the nucleoside adducts obtained following chemical and enzymatic digestion reveals an adduct pattern which is identical to that obtained by the reaction of poly(G) with (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[alpha]pyrene (diol-epoxide 2). The ratios of the diastereomeric pairs of cis- and trans-diolepoxide 2-guanosine adducts indicate that both enantiomers of (+/-)-BP-7,8-diol are metabolized to an equal extent.

Versatility of oxazolidine spin labels--a model study with acyl-alpha-chymotrypsin.

The p-nitrophenyl ester of N-oxyl-4',4'-dimethyl-3-oxazolidinebutyric acid was synthesized. The resonance spectrum of the acyl-alpha-chymotrypsin intermediate of this substrate was found to have more motional freedom at the enzyme active site as compared to the acyl-enzyme prepared from the p-nitrophenyl esters of 1-oxyl-2,2,5,5-tetramethyl-3-carboxypyrrolidine and 1-oxyl-2,2,6,6-tetramethyl-4-carboxy-1,2,5,6-tetrahydropyridine. The flexibility and the versatility of Keana's oxazolidine spin labels as covalent conformational probes is discussed.

Stereoselectivity of the epoxidation of 7,8-dihydrobenzo[a]pyrene by prostaglandin H synthase and cytochrome P-450 determined by the identification of polyguanylic acid adducts.

The stereoselectivity of the oxidation of 7,8-dihydrobenzo[a]pyrene (H2BP) to 9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (H4BP-epoxide) by prostaglandin H (PGH) synthase and cytochrome P-450 has been studied using microsomal preparations from ram seminal vesicles and rat liver. Incubations were performed in the presence of polyguanylic acid and the adducts formed between H4BP-epoxide and guanosine were isolated following the recovery and hydrolysis of the poly(G). When (+/-)-H4BP-epoxide was reacted with poly(G), four diastereomeric adducts were formed by the cis and trans addition of the exocyclic amino group of guanine to the benzylic carbon of the epoxide enantiomers. Each diastereomer was identified by a combination of ultraviolet, nuclear magnetic resonance, circular dichroism, and mass spectroscopy. Under comparable conditions, ram seminal vesicle microsomes in the presence of arachidonic acid triggered the binding of H2BP to poly(G) to a greater extent than rat liver microsomes from untreated and phenobarbital- and methylcholanthrene pretreated animals in the presence of NADPH. Quantitation of the (-)-cis- and (+)-cis-guanosine adducts revealed the degree of stereoselectivity of epoxidation. The ratio of (-)/(+) adducts was 54:46 for PGH synthase and 89:11 (control), 62:38 (phenobarbital), and 69:31 (methylcholanthrene) for cytochrome P-450-catalyzed reactions. PGH synthase catalyzed the epoxidation of H2BP with little or no stereoselectivity in contrast to cytochrome P-450. The utility of the poly(G) binding technique for the elucidation of the stereoselective generation of chiral electrophiles is discussed along with the mechanistic implications of the results.