4-Pregnen-21-ol-3,20-dione-21-(4-bromobenzenesufonate) (NSC 88915) and Related Novel Steroid Derivatives as Tyrosyl-DNA Phosphodiesterase (Tdp1) Inhibitors

Abstract

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is an enzyme that catalyzes the hydrolysis of 3'-phosphotyrosyl bonds. Such linkages form in vivo when topoisomerase I (Top1) processes DNA. For this reason, Tdp1 has been implicated in the repair of irreversible Top1-DNA covalent complexes. Tdp1 inhibitors have been regarded as potential therapeutics in combination with Top1 inhibitors, such as the camptothecin derivatives, topotecan and irinotecan, which are used to treat human cancers. Using a novel high-throughput screening assay, we have identified the C21-substituted progesterone derivative, NSC 88915 (1), as a potential Tdp1 inhibitor. Secondary screening and cross-reactivity studies with related DNA processing enzymes confirmed that compound 1 possesses specific Tdp1 inhibitory activity. Deconstruction of compound 1 into discrete functional groups reveals that both components are required for inhibition of Tdp1 activity. Moreover, the synthesis of analogues of compound 1 has provided insight into the structural requirements for the inhibition of Tdp1. Surface plasmon resonance shows that compound 1 binds to Tdp1, whereas an inactive analogue fails to interact with the enzyme. Based on molecular docking and mechanistic studies, we propose that these compounds are competitive inhibitors, which mimics the oligonucleotide-peptide Tdp1 substrate. These steroid derivatives represent a novel chemotype and provide a new scaffold for developing small molecule inhibitors of Tdp1.

Design, Synthesis, and Biological Evaluation of O-2-Modified Indenoisoquinolines as Dual Topoisomerase I–Tyrosyl-DNA Phosphodiesterase I Inhibitors

“…53 Therefore, the disappearance of the gel band for N14P indicates TDP1 inhibition. The TDP1 inhibitory activities of O-2-modified indenoisoquinolines are displayed in Table 1, and a representative gel demonstrating dose-dependent TDP1 inhibition is depicted in Figure 6.…”

Tyrosyl-DNA-phosphodiesterases (TDP1 and TDP2)

“…Its mechanism of action on TDP1 is therefore distinct from the known selective binding of furamidine to AT-rich sites in the minor groove of duplex DNA. Phosphotyrosine mimetics including methyl-3,4-dephostatin [152] and the steroid compound NSC88915 [157] were also discovered as submicromolar TDP1 inhibitors by HTS assays. These compounds bear either a hydroxyl-substituted benzyl ring or an aromatic sulfonyl ester group that simulate the phosphotyrosyl moiety present on the TDP1 DNA substrate.…”

Synthesis and biological evaluation of novel tyrosyl-DNA phosphodiesterase 1 inhibitors with a benzopentathiepine moiety

“…Steroid compound NSC 88915 appeared to be the most effective Tdp1 inhibitor among phosphotyrosine mimetics with IC 50 value 7.7 ± 0.8 lM. 29 Recently, a subset of indenoisoquinoline derivatives-Top1/Tdp1 dual inhibitors was discovered. 22 One bis(indenoisoquinoline) had significant activity against human Tdp1 (IC 50 = 1.52 ± 0.05 lM).…”