Synthesis of 11-aminoalkoxy substituted benzophenanthridine derivatives as tyrosyl-DNA phosphodiesterase 1 inhibitors and their anticancer activity

Abstract

Tyrosyl-DNA phosphodiesterase 1 (TDP1) is an enzyme that repairs DNA lesions caused by the trapping of DNA topoisomerase IB (TOP1)-DNA break-associated crosslinks. TDP1 inhibitors have synergistic effect with TOP1 inhibitors in cancer cells and can overcome cancer cell resistance to TOP1 inhibitors. Here, we report the synthesis of 11-aminoalkoxy substituted benzophenanthridine derivatives as selective TDP1 inhibitors and show that six compounds 14, 16, 18, 20, 25 and 27 exhibit high TDP1 inhibition potency. The most potent TDP1 inhibitor 14 (IC₅₀ = 1.7 ± 0.24 μM) induces cellular TDP1cc formation and shows synergistic effect with topotecan in four human cancer cell lines MCF-7, A549, H460 and HepG2.

Keywords: Anticancer; Benzophenanthridine; DNA repair; Topoisomerase; Tyrosyl-DNA phosphodiesterase.

Fig. 1.

The representative oxynitidine TDP1 inhibitors.

Fig. 2.

(A) Representative TDP1 inhibition gels of the active compounds. Lane 1, DNA alone; lane 2, DNA and recombinant TDP1; lanes 3–26, DNA, recombinant TDP1 and the active compounds at tested concentration. Tested concentrations were 0.051, 0.15, 0.46, 1.4, 4.1, 12.3, 37 and 111 μM. The Indenoisoquinoline TDP1 inhibitor 43 was used as the positive control. ³²P14Y and ³²P14P are the substrate and product of TDP1, respectively. (B) Induction of TDP1-DNA covalent complex by ICE assay in MCF-7 cells. Lane 1, untreated control; lanes 2–4, cells treated with TPT (10 μM), and 14 at 10 and 100 μM concentration, respectively; lanes 5 and 6, cells co-treated with TPT (10 μM) and 14 (10 and 100 μM), respectively.

Fig. 3.

Synergistic effect (Left panel) and the combination index (Right panel) of 14 with TPT in the four human cell lines MCF-7, A549, H460 and HepG2. The cells were co-incubated with drugs for 96 h.

Scheme 1.

Synthesis of 11–42. Reagents and conditions: (a) i) ICl, AcOH, rt; ii) MeOH, H2SO 4, 80 °C. (b) N 2, TMSA, PdCl 2(PPh 3) 2, CuI, TEA, THF, rt. (c) K 2CO 3, MeOH, rt. (d) i) AgNO 3, I 2, MeOH, rt; ii) KMnO 4, H 2O/MeCN, rt. (e) i) SOCl 2, reflux; ii) NH 3⋅H 2O, THF, rt. (f) N 2, PdCl 2(PPh 3) 2, TEA, MeCN, 80 °C. (g) i) N 2, Me 3OBF 4, DCM, rt; ii) CF 3CO 2Ag, DCM, rt. (h) K 2CO 3, MeOH, H 2O, 80 °C. (i) Ac 2O, AcOK, 140 °C. (j) N 2, R 1(CH 2) nCl or propargyl bromide (for 31), KI, K 2CO 3, DMF. (k) R 2N 3, CuSO 4⋅5H 2O, Sodium ascorbate, THF, H 2O, 50 °C.