Abstract LB-058: Linker variation and structure-activity relationship analyses of salicylic, benzoic and hydroxamic acid-based small molecule Stat3 inhibitors

Benzoic acid, salicylic acid and hydroxamic acid-based small molecules have been reported that inhibit Stat3 activation. However, the structural basis for their Stat3-inhibitory activities are not clearly defined. To investigate the molecular determinants for activity and to derive structurally optimized analogs of improved pharmacokinetic parameters and potency, we conducted a computer-aided molecule optimization program and synthesized new analogs of the previously reported lead Stat3 inhibitors, BP-1-102 (IC50, 6.8 ± 2.5), SH4-54 (IC50 4.4 ± 0.3), and SH5-07 (IC50 3.9 ± 0.6). All three leads are based on N-methylglycinamide scaffold with its two amine moieties condensed with three different functionalities. The three functionalities or the CH2 group of the glycolamide scaffold were separately modified to generate a series of compounds, some of which show improved potency compared to the corresponding parental compounds. Specifically, H012, H070 and H072 had improved inhibitory activity against Stat3 DNA-binding activity in vitro, with IC50 of 3.0 ± 0.9, 2.4 ± 0.4, and 2.2 ± 0.9 μM, respectively. The replacement of the pentafluorobenzene or the cyclohexylbenzene with other components was detrimental to activity and led to decreased potency of the new analogues, as did the substitution of the benzene of the pTyr-mimetic moiety with heterocyclic components containing nitrogen and oxygen elements. Pharmacokinetic study showed that analog H058 has improved permeability in Caco-2 bidirectional permeability studies, compared to the lower relative permeability of the lead agents. Ala-based analogs, such as H048 and H058, were low in microsomal stability, presumably due to the labile methyl groups of the Ala. Select active analogs inhibited constitutive Stat3 activation and the DNA-binding activity of Stat3 in cancer cells, and they further decreased the growth, colony formation, and migration of human cancer cells harboring persistently active Stat3. Studies together demonstrate a significant progress towards developing a more suitable Stat3 inhibitor with drug-like features. Additional efforts are focused on refining the physicochemical properties to further improve the activity and efficacy and ultimately furnish suitable Stat3-inhibiting candidates for clinical application. Citation Format: Peibin Yue, Francisco Lopez-Tapia, Christine Brotherton-Pleiss, Marcus Tius, James Turkson. Linker variation and structure-activity relationship analyses of salicylic, benzoic and hydroxamic acid-based small molecule Stat3 inhibitors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-058.