Analogues of N^α-(4-Amino-4-deoxypteroyl)-N^δ-hemiphthaloyl-l-ornithine (PT523) Modified in the Side Chain:  Synthesis and Biological Evaluation

Abstract

Four heretofore undescribed side chain analogues of N alpha-(4-amino-4-deoxypteroyl)-N delta-hemiphthaloyl-L-ornithine (PT523, 4) were synthesized via straightforward methods of antifolate chemistry, and their properties were compared with those of PT523 and two related compounds with the aim of defining the contribution of the hemiphthaloyl-L-ornithine moiety to the exceptional in vitro antitumor activity of this novel non-polyglutamatable aminopterin analogue. The IC50 values of N alpha-(4-amino-4-deoxypteroyl)-N beta-hemiphthaloyl-L-2,3-diaminopropanoic acid (10) and N alpha-(4-amino-4-deoxypteroyl)-N gamma-hemiphthaloyl-L-2,4- diaminobutanoic acid (9) against A549 human non-small-cell lung carcinoma cells in culture were 23 and 22 nM, whereas those of PT523 and N alpha-(4-amino-4-deoxypteroyl)-N epsilon-hemiphthaloyl-L-lysine (8) were 1.3 and 5.2 nM. A decrease in the in vitro activities of 8 and 9 relative to PT523 was also observed against the panel of cell lines used by the National Cancer Institute to screen new drugs. However the potency of 8 and 9 remained several times greater than that of the historical control methotrexate against many of the cell lines in the screening panel. In an in vivo tumor model, SCC-VII murine squamous cell carcinoma, 9 and methotrexate were well tolerated as 5-day continuous infusions at doses of 0.52 and 0.75 mg/kg/day, whereas the highest tolerated dose of PT523 on this schedule was 0.19 mg/kg/day, in agreement with its lower IC50 in culture. To assess the importance of the hemiphthaloyl group in PT523, N alpha-(4-amino-4-deoxypteroyl)-N delta-isophthaloyl-L-ornithine (11), N alpha-(4-amino-4-deoxypteroyl)-N delta-terephthaloyl-L-ornithine (12), and N alpha-(4-amino-4-deoxypteroyl)-N delta-(4,5-dichlorohemiphthaloyl)-L-ornithine (13) were also synthesized. The IC50 values of 11 and 12 against A549 cells were 45 and 3300 nM, as compared with 1.3 nM for PT523 and 23 nM for methotrexate. In a clonogenic assay against SCC25 human squamous cell carcinoma cells, the IC50 values of 11 and 12 were 2.9 and 72 nM, as compared with 0.3 nM for PT523 and 27 nM for methotrexate. Thus, activity was decreased by moving the aromatic carboxyl group in PT523 to the meta position and was further diminished by moving it to the para position. The IC50 of the halogenated analogue 13 against SCC25 human head and neck squamous carcinoma cells was 18 nM, suggesting lack of tolerance for this 4,5-disubstitution in the phthaloyl moiety. Our results suggest that the combination of a hemiphthaloyl group and three CH2 groups in the side chain are critical determinants of the potent in vitro activity of PT523.

Dimerization and comments on the reactivity of homophthalic anhydride

“…Furthermore, the C-1 anhydride carbonyl, which is conjugated with the HPA benzo portion, should also be less reactive than C-3. Reactions of HPA preferentially at C-3 with various nucleophiles such as tert -butylamine, 12 methoxide, 13 and a wide variety of anilines, 14,15 besides HPA itself (Scheme 4), confirm the greater C-3 reactivity.…”

NMR and NBO calculation of benzimidazoles and pyrimidines: Nano physical parameters investigation

“…E-mail: m_monajjemi@yahoo.com antiulcerative, anti-hypertensive, antiviral, antifungal, antitumor and antihistaminic agents, and antihelminthic agents in veterinary medicine (Spasov et al, 1999). Benzimidazole derivatives have found the appreciation in diverse therapeutic areas including antimicrobial activity Wu et al, 2003;Mollaamin et al, 2008;Ozden et al, 2005;Sztanke et al, 2006), the activity against several viruses such as HIV (Porcari et al ., 1998;Samia et al, 2006), antiallergic (Kilcig and Altanlar, 2006;Nakano et al, 1999), antioxidant, antihistaminic (Vijayakumar and Jafar Ahamed, 2010), antitubercular (Yadav and Srivastava, 2011;Kuchkguzel et al, 2001), antiasthmatic (Souness et al, 2000), antidiabetic (Senten et al, 2003;Black et al, 2005), anticancer (Pal et al, 2011;Sun et al, 2011;Kruse et al,1989;Islam et al,1991;Ramla et al,2007), antitumor (Denny et al, 1990 ;Tatsuta et al, 2005), antiulcer (Jung et al, 1993;Hazelton et al, 1995), antihelmentic (Karen, 2006), HIV-1 reverse transcriptase inhibitors (Gardiner et al, 2003), anticoagulant (Young et al, 2006), anti inflammatory (Fox et al, 2009), antibacterial (Rosowsky et al, 1997;Andrzejewska et al, 2004) , the series of biologically active benzimidazoles (AJafar et al,2009). Furthermore, these heterocycles are considered to be privileged structures by medicinal chemists.…”

Synthesis and Potent Antifolate Activity and Cytotoxicity of B-Ring Deaza Analogues of the Nonpolyglutamatable Dihydrofolate Reductase Inhibitor Nα-(4-Amino-4-deoxypteroyl)-Nδ-hemiphthaloyl-l-ornithine (PT523)

“…As part of a broader effort to identify the structural features responsible for the unusually potent in vitro antitumor activity of PT523, we recently synthesized analogues of PT523 in which the number of CH 2 groups in the side chain was either shortened ( 4 , 5 ) or lengthened ( 6 ) . Also synthesized were the 3‘,5‘-dichloro analogue 7 and the isophthaloyl and terephthaloyl analogues 8 and 9 .…”