Total Synthesis, Mechanism of Action, and Antitumor Efficacy of Camptothecin and Some of its Analogues.

Over the past 55 years of research, various experimental methods have been developed for the total synthesis of the anticancer camptothecin, a potent antitumor antibiotic, and its numerous active derivatives. The discoveries made in synthetic pathways of the camptothecin heterocyclic core have contributed significantly to the theory and strategy of directed organic synthesis aimed at finding effective anticancer drugs. The synthetic, medicinal chemistry of camptothecin, the development of structures of anticancer camptothecin analogues, and the mechanism of their activity in inhibiting the growth of different types of cancers, such as lung, ovarian, breast, pancreas, and stomach cancers are analyzed. Various structural modifications in the A, B, C, D, and E-rings of the camptothecin molecule have been thoroughly studied to improve bioavailability and diminish toxicity. Modern synthetic approaches to the camptothecin analogues and several semi-synthetic methods are reviewed.

Design, Synthesis, and Biological Evaluation of Peptidomimetic N-Substituted Cbz-4-Hyp-Hpa-Amides as Novel Inhibitors of Plasmodium falciparum.

A new series of peptidomimetic N-substituted Cbz-4-Hyp-Hpa-amides were designed, synthesized, and evaluated for inhibition of the Plasmodium falciparum. Substituents on the N-atom of the amide group were selected alkyl-, allyl-, aryl-, 2-hydroxyethyl-, 2-cyanoethyl-, cyanomethyl-, 2-hydroxyethyl-, 2,2-diethoxyethyl-, or 2-ethoxy-2-oxoethylamino groups, and about of 40 new compounds were synthesized and evaluated for antiplasmodial activity in vitro. Antimalarial activity has been investigated as for the final peptide mimetics, and their immediate predecessors, carrying TBDMS or TBDPS protecting groups on 4-hydroxyproline residue and 18 derivatives exhibited toxicity against P. falciparum. Of these agents, compound 23e was shown to have potent antimalarial activity with IC50 528 ng/ml.

Dr. Samokhotskiy's method of healing inflammation by the analysis and regulation of blood electrolyte balance.

An overview of a little-known method, which was discovered by Dr. Alexander S. Samokhotskiy, for treatment of gangrenous, traumatic, and postoperative inflammation, sepsis and some other diseases, was represented. Dr. A. S. Samokhotskiy carried out numerous animal experiments and clinical trials and found that application of wet bandages and/or intravenous injection of solution containing trivalent chromium ions (Cr3+), alum, resorcinol, sodium salicylate, lactate buffer, colloidal sulphur, thioglycolic acid and glutathione with adding KCl, MgCI2, CaCl2 or NaCl solutions can heal inflammation of various etiology. Intravenous injections of particular therapeutic solution containing Na+, K+, Ca2+ or Mg2+ ions were administered in dependence on concentration of these ions in patient's blood plasma. Thousands of patients, many of them with fatal afflictions, where other methods were helpless, were healed by Dr. A. S. Samokhotskiy with the help of his method. Purpose of this publication is to inform the international medical community with the Dr. A. S. Samokhotskiy's discovery and initiate further research in this area.

Potent antitumor 9-anilinoacridines and acridines bearing an alkylating N-mustard residue on the acridine chromophore: synthesis and biological activity.

A series of 9-anilinoacridine and acridine derivatives bearing an alkylating N-mustard residue at C4 of the acridine chromophore were synthesized. The N-mustard pharmacophore was linked to the C4 of the acridine ring with an O-ethyl (O-C(2)), O-propyl (O-C(3)), or O-butyl (O-C(4)) spacer. It revealed that all newly synthesized compounds were very potent cytotoxic agents against human leukemia and various solid tumors in vitro. These agents did not exhibit cross-resistance against vinblastine-resistant (CCRF-CEM/VBL) or taxol-resistant (CCRF-CEM/taxol) cells. It also showed that these agents were DNA cross-linking agents rather than topoisomerase II inhibitors. Of these agents, compounds 27a and 27c were shown to have potent antitumor activity in nude mice bearing the human breast carcinoma MX-1 xenograft. The therapeutic efficacies of these two agents are comparable to that of taxol.

Synthesis and antitumor activity of 5-(9-acridinylamino)anisidine derivatives.

A series of 5-(9-acridinylamino)anisidines were synthesized by condensing methoxy-substituted 1,3-phenylenediamines (10 and 11) with 9-chloroacridine derivatives to form 5-(9-acridinylamino)-m-anisidines (AMAs, 14a-e) and 5-(9-acridinylamino)-o-anisidines (AOAs, 15a-e). 5-(9-Acridinylamino)-p-anisidines (APAs, 17a-e) were synthesized by reacting 2-methoxy-5-nitroaniline (12) with 9-anilinoacridines, followed by reduction. The cytotoxic inhibition of growth of various human tumor cells in culture, inhibitory effects against topoisomerase II, and DNA interaction of these agents were studied. The structure-activity relationship studies revealed the following degree of potency: AOAs > AMAs > APAs. They also revealed that the newly synthesized derivatives bearing CONH(2)NH(2)NMe(2) and Me substituents at C4 and C5 positions of the acridine chromophore (i.e., AMA 14e, AOA 15e, and APA 17e) exhibited significant cytotoxicity against human tumor cell growth in vitro. AOA (15e) was the most potent among these derivatives, which resulted in 60% suppression of tumor volume at a dose of 20 mg/kg (Q2D x 9), intravenous injection on day 26 in nude mice bearing human breast carcinoma MX-1 xenografts.

Potent antitumor 9-anilinoacridines bearing an alkylating N-mustard residue on the anilino ring: synthesis and biological activity.

A series of N-mustard derivatives of 9-anilinoacridine was synthesized for antitumor and structure-activity relationship studies. The alkylating N-mustard residue was linked to the C-3' or C-4' position of the anilino ring with an O-ethylene (O-C(2)), O-butylene (O-C(4)), and methylene (C(1)) spacer. All of the new N-mustard derivatives exhibited significant cytotoxicity in inhibiting human lymphoblastic leukemic cells (CCRF-CEM) in culture. Of these agents, (3-(acridin-9-ylamino)-5-{2-[bis (2-chloroethyl)amino]ethoxy}phenyl)methanol (10) was subjected to antitumor studies, resulting in an approximately 100-fold more potent effect than its parent analogue 3-(9-acridinylamino)-5-hydroxymethylaniline (AHMA) in inhibiting the growth of human lymphoblastic leukemic cells (CCRF-CEM) in vitro. This agent did not exhibit cross-resistance against vinblastine-resistant (CCRF-CEM/VBL) or Taxol-resistant (CCRF-CEM/Taxol) cells. Remarkably, the therapeutic effect of 10 at a dose as low as one tenth of the Taxol therapeutic dose [i.e., 1-2mg/kg (Q3Dx7) or 3mg/kg (Q4Dx5); intravenous injection] on nude mice bearing human breast carcinoma MX-1 xenografts resulted in complete tumor remission in two out of three mice. Furthermore, 10 yielded xenograft tumor suppression of 81-96% using human T-cell acute lymphoblastic leukemia CCRF-CEM, colon carcinoma HCT-116, and ovarian adenocarcinoma SK-OV-3 tumor models.

Potent antitumor N-mustard derivatives of 9-anilinoacridine, synthesis and antitumor evaluation.

A series of 9-anilinoacridine N-mustard derivatives, in which the alkylating N-mustard residue was linked to the C-3' or C-4' position of the anilino ring with an O-ethylene spacer, was synthesized and evaluated for cytotoxicity against human lymphoblastic leukemic cells (CCRF-CEM) in culture. The results showed that all of the new compounds exhibited potent cytotoxicity with IC(50) values ranging from 0.002 to 0.7 microM, which were as potent or significantly more potent than 3-(9-acridinylamino)-5-hydroxymethylaniline (AHMA). Compound 9 did not exhibit cross-resistance against both vinblastine-resistant (CCRF-CEM/VBL) and taxol-resistant (CCRF-CEM/taxol) cells. Additionally, compound 9 demonstrated potent antitumor effect in nude mice bearing human breast carcinoma MX-1 xenografts, resulting in complete tumor remission in two out of three mice at the maximal dose of 1-2mg/kg (Q3Dx7) or 3mg/kg (Q4Dx5) via intravenous injection.

New analogues of AHMA as potential antitumor agents: synthesis and biological activity.

A series of new analogues of 3-(9-acridinylamino)-5-hydroxymethylaniline (AHMA, 1) and AHMA-ethylcarbamate (2) were synthesized by introducing an O-alkylcarboxylic acid esters to the CH(2)OH function, displacing the CH(2)OH function with a dimethylaminocarboxamido group or with a methyl function introduced at the meta-, para- or ortho-position to the NH(2) group to form 5-(9-acridinylamino)-m-toluidines (AMTs), 5-(9-acridinylamino)-p-toluidines (APTs) or 5-(9-acridinylamino)-o-toluidines (AOTs), respectively. The inhibitions of a variety of human tumor cell growth, interactions with DNA as well as inhibitory effect against topoisomerase II (Topo II) of these new agents were studied. Among AMT, APT and AOT derivatives with dimethylaminoethylcarboxamido and Me at C4 and C5 of acridine moiety (i.e., 21c, 23c and 26c) were more cytotoxic than AHMA (1) and AHMA-ethylcarbamate (2), depending upon the tumor cell line tested. Detailed structure-activity relationships of the new analogues were studied.

Non-classical antifolates, 5-(N-phenylpyrrolidin-3-yl)-2,4,6-triaminopyrimidines and 2,4-Diamino-6(5H)-oxopyrimidines, synthesis and antitumor studies.

A series of non-classical antifolates, namely 5-(N-phenylpyrrolidin-3-yl)-2,4,6-triaminopyrimidines (25a-i) and 2,4-diamino-(N-phenylpyrrolidin-3-yl)-6(5H)-oxopyrimidines (26a,b,c,f,h,i) was synthesized and evaluated for their in vitro cytotoxicity. Reacting aniline derivatives with 1,4-dibromo-2-butanol gave 1-phenyl-3-pyrrolidinols (19a--i), which were oxidized to pyrrolidin-3-ones (20a-i). The Knoevenagel reaction of 20a-i with malononitrile or ethyl cyanoacetate gave 3-(dicyanomethylene)- (21a-i) and 3-[cyano(ethoxycarbonyl)methylene]-pyrrolidines (22a,b,c,f,h,i), respectively, which were subsequently reduced to the corresponding 3-(dicyano)methyl- or 3-[cyano(ethoxycarbonyl)methyl)]pyrrolidines (23a-i and 24a,b,c,f,h,i, respectively). Condensation of either 23a-i or 24a,b,c,f,h,i with guanidine afforded the target compounds. The cytotoxicity of these compounds was evaluated based on their ability to inhibit various human tumors (human colon adenocarcinoma COLO 205, lung carcinoma H23 and its adriamycin resistant cell line H23/0.3, T-cell leukemia MOLT-4, promyelocytic leukemia HL-60, and T-cell acute lymphocytic leukemia CCRF-CEM) cell growth in culture. These studies revealed that the 2,4,6-triaminopyrimidine derivatives were more cytotoxic than the 2,4-diamino-6(5H)-oxopyrimidine counter parts, in which the latter was inactive in all testing systems. The 2,4,6-triaminopyrimidine derivatives bearing halogen substituent on the phenyl ring (25f,h,i) were cytotoxic in all cultured leukemia cell growth. Among these compounds, 5-(4-fluoro and 4-chlorophenyl)-2,4,6-triaminopyrimidines (25e and 25h, respectively) were more potent than methotrexate (MTX) in inhibiting of H23/0.3 cell growth. These compounds inhibit the folate metabolic pathways as indicated by tritium release from [5-3H]deoxyuridine in MTX sensitive human fibrosarcoma HT-1080 cells. Dihydrofolate reductase is the major target for 25f,h,i, as shown by leucovorin (LV) rescue of MTX cytotoxicity.