2-(aminoalkyl)-5-nitropyrazolo[3,4,5-kl]acridines, a new class of anticancer agents.

2-(Aminoalkyl)-5-nitropyrazolo[3,4,5-kl]acridines were prepared from substituted anilines via the 1-chloro-4-nitroacridones followed by condensation with [(alkylamino)alkyl]hydrazines. Impressive activity was demonstrated for the 9-hydroxy, 9-alkoxy, and 9-acyloxy analogs in vitro on a L1210 leukemia line and in vivo against the P388 leukemia. Advanced studies led to the selection of 3bbb for clinical trial.

Synthesis and antimalarial properties of 1-imino derivatives of 7-chloro-3-substituted-3,4-dihydro-1,9(2H,10H)-acridinediones and related structures.

To improve upon the activity and properties of the 3-aryl-7-chloro-3,4- dihydro-1,9(2H,10H)-acridinediones, a variety of 1-[(alkylamino)alkylene]imino derivatives (3) were prepared and shown to be highly active antimalarial agents in both rodents and primates. Among structural modifications prepared, including N10-alkyl and C2-substituted analogs, removal of the C9 oxygen, and introduction of an imino side chain at C9, the imines of the N10-H acridinediones were the most active compounds obtained. The [3-(N,N- dimethylamino)propyl]imino derivative of 7-chloro-3-(2,4-dichlorophenyl)-3,4-dihydro-1,9(2H,10H)- acridinedione (9aa) proved to be highly active in advanced studies in primates.

A new class of analogues of the bifunctional radiosensitizer alpha-(1-aziridinylmethyl)-2-nitro-1H-imidazole-1-ethanol (RSU 1069): the cycloalkylaziridines.

A series of compounds related to alpha-(1-aziridinylmethyl)-2-nitro-1H-imidazole-1-ethanol (RSU 1069, 1) were synthesized and evaluated as selective hypoxic cell cytotoxic agents and as radiosensitizers. The aziridine moiety was replaced with a number of other potential alkylating groups including cycloalkylaziridines and azetidines. The data indicated that modification of the aziridine of 1 resulted in a substantial decrease in the ability of the compounds to selectively kill hypoxic cells. However, these modifications did not affect the compounds' in vitro radiosensitizing activity since many of the derivatives were as potent as 1. All of the compounds that were evaluated in vivo were less toxic than 1, and several members of this series had significant activity. The best compound was trans-alpha-[[(4-bromotetrahydro-2H-pyran-3-yl) amino]methyl]-2-nitro-1H-imidazole-1-ethanol (18), which, due to its activity and log P value, is a candidate for additional in vivo studies.

Dihydroisoquinolinones: the design and synthesis of a new series of potent inhibitors of poly(ADP-ribose) polymerase.

A series of dihydroisoquinolinones, formally rigid analogs of 3-substituted benzamides, and a series of 2,3-disubstituted benzamides were synthesized and evaluated as inhibitors of poly(ADP-ribose) polymerase. The results indicated that the orientation of the amide with respect to the substituent on the aromatic ring was critical for optimum inhibitory activity. Selected compounds were also evaluated for their ability to modify the radiation response of mammalian cells to ionizing radiation. A number of the 5-substituted dihydroisoquinolinones, which were very potent inhibitors of the enzyme, were able to enhance the lethal effects of ionizing radiation in mammalian cells, as measured by changes in the survival curve parameters Do and/or Dq.

Dual-function radiosensitizers. Alpha-[[(2-bromoethyl)amino]methyl]-2-nitro-1H-imidazole-1-ethanol and related compounds: preparation via an aziridine equivalent.

An improved synthesis of the dual-function radiosensitizer alpha-[[(2-bromoethyl)amino]methyl]-2-nitro-1H-imidazole-1-ethanol (2, RB 6145) has been developed. Previously, the synthetic difficulties associated with this compound limited its attractiveness as a clinical candidate, although its radiosensitizing activity in preclinical models warranted its further development. The synthesis described uses a 2-oxazolidinone as an aziridine equivalent and provides 2 in 47% yield.

Synthesis and antiarrhythmic activity of alpha-[(diarylmethoxy)methyl]-1-piperidineethanols.

A series of alpha-[(diarylmethoxy)methyl]-1-piperidineethanols was evaluated for antiarrhythmic activity in the coronary artery ligated dog model. Structure-activity relationship studies indicated that the 2,6-dimethylpiperidine group afforded the best antiarrhythmic agents in this series and was essential for long duration of action. This investigation indicated that quaternary ammonium salts were not essential for a long duration of action. It was also shown that the antiarrhythmic activity could be separated from the tachycardia frequently caused by this type of agent.

Antitumor efficacy of PD115934 (NSC 366140) against solid tumors of mice.

PD115934 (NSC 366140) is a soluble pyrazoloacridine derivative presently undergoing preclinical toxicology evaluation with the anticipation of Phase I human investigation. The agent displayed both human and murine solid tumor selectivity in vitro in a soft agar disk diffusion assay, relative to its activity against murine L1210 leukemia. In vivo it was highly active against solid tumors colon adenocarcinoma 38 and pancreas ductal carcinoma 03, which was consistent with the cellular cytotoxicity seen in the disk diffusion assay. A log cell kill of greater than 4.0 was demonstrated in vivo against both models. PD115934 was administered by both bolus and infusional therapy. After completion of these trials, it was determined that this compound was a schedule category III agent, i.e., a schedule-independent agent with peak plasma level toxicity. The main toxicity encountered with infusional therapy was myelosuppression. With bolus therapy, central nervous system toxicities were dose limiting. On the basis of our preclinical infusion studies, we recommend a 2-h infusion twice weekly in humans in order to obtain a total dose of 360 mg/m2 over 8 weeks.

Potent inhibition of thymidylate synthase by two series of nonclassical quinazolines.

The synthesis and biological activity of two series of nonclassical thymidylate synthase (TS) inhibitors are described. The first is a series of 10-propargyl-5,8-dideazafolic acid derivatives (10a-j) and the second is a series of the analogous 2-desamino derivatives (13a-c,k), both bearing a more lipophilic substituent on the phenyl ring than the CO-glutamate of classical antifolates. Compounds 10a-j were prepared in a straightforward manner, generally by treatment of N-[6-(bromomethyl)-3,4-dihydro-4-oxo-2-quinazolinyl]-2,2-dimethylprop anamide (6) with various phenyl-substituted N-propargylanilines (8), followed by deprotection. Compounds 13a-c,k were prepared similarly from [6-(bromomethyl)-4-oxo-3(4H)-quinazolinyl] methyl 2,2-dimethylpropanoate (11). The compounds were tested for inhibition of purified L1210 TS and for inhibition of L1210 cell growth in vitro. Several of these nonclassical analogues approached the TS inhibitory potency of 10-propargyl-5,8-dideazafolic acid (1, CB3717), a glutamate-containing TS inhibitor. 2-Amino target compounds 10a-j were generally potent inhibitors of L1210 TS, with IC50s within the range of 0.51-11.5 microM, compared to 0.05 microM for 1. The order of potency for phenyl substitution at the 4-position in this series was the following: COCF3 greater than or equal to NO2 greater than or equal to CONH2 greater than or equal to COCH3 greater than SO2NMe2 greater than CN much greater than OCF3 greater than or equal to F. The 2-desamino target compounds 13a-c,k also exhibited significant, although diminished, TS inhibition. Both series were growth inhibitory to cells in tissue culture and this inhibition could be reversed by thymidine alone, indicating that the primary target was TS. None of the compounds was a potent inhibitor of dihydrofolate reductase. These studies indicate that the presence of the glutamate moiety in folate analogues is not an absolute requirement for potent inhibition of TS.

Benzothiopyranoindazoles, a new class of chromophore modified anthracenedione anticancer agents. Synthesis and activity against murine leukemias.

The synthesis of the benzothiopyranoindazoles, a new class of chromophore modified anthracenediones related to mitoxantrone, is described. In this structural class the quinone moiety, which is believed to be responsible for the cardiotoxicity of the anthracyclines, has been designed out. The synthesis of the benzothiopyranoindazoles was carried out by a multistep sequence from requisite 1-chloro-4-nitro-9H-thioxanthen-9-one precursors. Reaction with a monoalkylhydrazine gave a 5-nitrobenzothiopyranoindazole adduct, which was catalytically reduced to a corresponding C-5 anilino intermediate. Alkylation of 7 with a requisite X(CH2)nNR1R2 (X = Cl, Br; R1, R2 = H, alkyl, acyl; n = 2,3) provided target "two-armed" benzothiopyranoindazoles or A-ring methoxy and/or side chain acyl intermediates, which could be converted to 3 by appropriate deprotection methodologies. Alternatively, certain target compounds 3 were synthesized by reaction of 7 with appropriately functionalized glycine precursors under Schotten-Bauman or BOP chloride condensation conditions to provide C-5 acylamino intermediates, followed by Red-Al reduction and deprotection steps. Described also is the synthesis of selected benzothiopyranoindazole congeners with proximal acylamino side chains at C-5 and B-ring sulfone functionality at S-6. Potent activity was demonstrated against murine L1210 leukemia in vitro (IC50 = 10(-7)-10(-9) M) as well as against P388 leukemia in vivo over a wide range of structural variants. In general, activity against the P388 line was maximized by (a) a basic side chain at N-2 and a dibasic side chain at C-5 with primary or secondary distal amine substitution, (b) certain patterns of A-ring hydroxylation with 8-OH and 9-OH most favorable, and (c) sulfide oxidation state at S-6. Besides having curative activity against the P388 line, the more active compounds were curative against murine B-16 melanoma in vivo. On the basis of their exceptional broad-spectrum in vivo anticancer activity, selected compounds in this series have been chosen for development toward clinical trials.

Antimalarial activity of 2-(substituted amino)-4,6-bis(trichloromethyl)-1,3,5-triazines and N-(chlorophenyl)-N'-[4-(substituted amino)-6-(trichloromethyl)-1,3,5-triazin-2-yl]guanidines.

A series of 2-[[(dialkylamino)alkyl]amino]-4,6-bis(trichloromethyl)-1,3,5-triazines (III) and N-(4-chlorophenyl)-N'-[4-[[(dialkylamino)alkyl]amino]-6- (trichloromethyl)-1,3,5-triazin-2-yl]guanidines (IV) were prepared from 2,4,6-tris(trichloromethyl)-1,3,5-triazine and 2-chloro-4,6-bis(trichloromethyl)-1,3,5-triazine. Compounds of type III showed modest antimalarial activity while XIa with the camoquin side chain was more potent. Analogues of type IV broadly exhibited modest antimalarial activity.

Synthesis and antimalarial and antitumor effects of 2-amino-4-(hydrazino and hydroxyamino)-6-[(aryl)thio]quinazolines.

A variety of analogues of 2,4-diamino-6-[(aryl)thio]quinazolines with known antimalarial properties were prepared wherein the 4-amino group was replaced by hydrazino and hydroxyamino moieties. Such changes were found to reduce markedly the antimalarial and antitumor properties of this series.

Synthesis and antimalarial effects of 4-[(7-chloro-4-quinolinyl)amino]-2-[(diethylamino)methyl] -6-alkylphenols and their N omega-oxides.

A series of 4-[(7-chloro-4-quinolinyl)amino]-2-[(diethylamino)methyl]-6-alkylphenols and their N omega-oxides were synthesized by the condensation of 4,7-dichloroquinoline and 4,7-dichloroquinoline N omega-oxide with appropriately substituted 4-amino-2-[(diethylamino)methyl]-6-alkylphenol dihydrochlorides. The latter precursors were prepared in a six-step synthesis starting from available 2-alkylphenols. Several of the title compounds display potent antimalarial activity in mice.

Anthrapyrazole anticancer agents. Synthesis and structure-activity relationships against murine leukemias.

Chromophore modification of the anthracenediones related to mitoxantrone in an attempt to provide agents with diminished or no cardiotoxicity has resulted in a novel class of DNA binders, the anthrapyrazoles. Their synthesis was carried out by a two-stage condensation sequence starting from requisite 1,4- or 1,5-dichloro-9,10-anthracenedione precursors. Reaction with a monoalkylhydrazine gave a chloroanthrapyrazole intermediate whose subsequent condensation with primary or secondary alkylamines provided the target "two-armed" anthrapyrazoles. A-ring 7,10-dihydroxy anthrapyrazoles were derived from amine condensation with intermediate 5-chloro-7,10-dihydroxyanthrapyrazoles or, alternatively, from intermediate 5-chloro-7,10-bis(benzyloxy)anthrapyrazoles followed by hydrogenolysis of the benzyl protecting groups to provide the target compounds. Potent in vitro activity was demonstrated against murine L1210 leukemia in vitro (IC50 = 10(-7)-10(-8) M) as well as against P388 leukemia in vivo over a wide range of structural variants. In general, activity against the P388 line was maximized by basic side chains at N-2 and C-5, two to three carbon spacers between proximal and distal nitrogens of the side chain, and A-ring hydroxylation. Besides having curative activity against the P388 line, the more active compounds were curative against murine B-16 melanoma in vivo. On the basis of their exceptional in vivo anticancer activity, A-ring dihydroxy compounds 71 and 74 reported in this study have been selected for development toward clinical trials.

Pyrazole derivatives. 5. Synthesis and antineoplastic activity of 3-(2-chloroethyl)-3,4-dihydro-4-oxopyrazolo[5,1-d]-1,2,3, 5-tetrazine-8-carboxamide and related compounds.

Two pyrazolotetrazine derivatives were synthesized as the analogous prodrugs of the light-sensitive antineoplastic agents dacarbazine and BIC. Both the pyrazole derivatives are stable under ordinary light illumination. Biological evaluation of these pyrazoles revealed that the compound containing a 2-chloroethyl function (6a) demonstrated good antineoplastic activity in experimental animals, but the one containing a methyl function (6b) was inactive. The inactivity of compound 6b may suggest that compound 6a and related imidazotetrazines may simply act as biological alkylating agents per se rather than as prodrugs. The information could also imply that the postulated dealkylation mechanism for the triazene derivatives should be reexamined.

Basically substituted ellipticine analogues as potential antitumor agents.

Installation of a basic side chain on the ring nitrogen of ellipticine did, as expected, improve the DNA binding properties of these molecules as measured by an ethidium displacement assay. In vivo antitumor activity was not, however, improved.

Synthesis, antimalarial activity, and quantitative structure-activity relationships of tebuquine and a series of related 5-[(7-chloro-4-quinolinyl)amino]-3-[(alkylamino)methyl] [1,1'-biphenyl]-2-ols and N omega-oxides.

A series of 5-[(7-chloro-4-quinolinyl)amino]-3-[(alkylamino)methyl] [1,1'-biphenyl]-2-ols and N omega-oxides was prepared from the substituted 1-phenyl-2-propanones proceeding through the 5-nitro[1,1'-biphenyl]-2-ols, the corresponding amino, and acetamido derivatives to the N-[5-[(alkylamino)methyl]-6-hydroxy[1,1'-biphenyl]-3-yl]acetamides and final condensation with 4,7-dichloroquinoline or the N-oxide. In a quantitative structure-activity relationship study first run on 28 and later expanded to 40 substituted phenyl analogues and their N omega-oxides, increasing antimalarial potency vs. Plasmodium berghei in mice was found to be correlated with decreasing size (sigma MR) and electron donation (sigma sigma) of the phenyl ring substituents. A significant correlation with N omega-oxidation could not be demonstrated. Initial high activity against P. berghei infections in mice led to expanded studies that demonstrated in addition excellent activity against resistant strains of parasite, activity in primate models, and pharmacokinetic properties apparently allowing protection against infection for extended periods of time even after oral administration. Such properties encourage the clinical trial of a member of this class in man.

Novel bis[1,6-dihydro-6,6-dimethyl-1,3,5-triazine-2,4-diamines] as antitrypanosomal agents.

A series of novel 1,1'-(4,1-phenylene)bis [1,6-dihydro-6,6-dimethyl-1,3,5-triazine-2,4-diamines] was prepared and evaluated for activity against Trypanosoma rhodesiense in mice. The importance of the bis structure and the nature of the spacer between the two phenyl rings for optimal activity have been revealed. The potent parenteral activity of several analogues within this series as well as preliminary indication of oral activity lends encouragement to further development of this structural class.

Folate antagonists. 21. Synthesis and antimalarial properties of 2,4-diamino-6-(benzylamino)pyrido[3,2-d]pyrimidines.

The synthesis and antimalarial activity of a series of 2,4,6-triaminopyrido[3,2-d]pyrimidines (4) is described. Several 6-substituted benzylmethylamino analogues were more active against trophozoite induced Plasmodium berghei in mice than the corresponding quinazoline analogues. These agents, however, are cross-resistant to other antifolate compounds and are thus of limited potential as human agents.

Folate antagonists. 22. Antimalarial and antibacterial effects of 2,4-diamino-6-quinazolinesulfonamides.

The synthesis and antimalarial activity of a series of 2,4-diamino-6-quinazolinesulfonamides (III) is described. Chlorosulfonation of 2,4-quinazolinediamine affords the 6-sulfonyl chloride, which upon treatment with the appropriate amine produces the desired products. Alternatively the sulfonyl chloride could be introduced by diazotization of the corresponding amine followed by treatment with SO2 in the presence of CuCl2. Although substantial antimalarial activity was demonstrated for several members of this class, studies were discontinued in light of the potency of related series.