Abstract Toll-like receptors 7 and 8 (TLR7/8) are innate immune sensors whose activation by endogenous RNA ligands is a hallmark of chronic autoimmune disorders, notably cutaneous and systemic lupus. We present the structure-based design and optimization of 2-(pyridin-2(1H)-one)indoles as potent dual TLR7/8 antagonists with properties improved over our prior series, including increased permeability, reduced ion channel activity, and reduced volume of distribution at steady state (Vss). Initial pyridone leads displayed unexpected anti-proliferative activity in a panel of immune cell lines; optimization against an identified off-target BRD4 liability, hypothesized to drive this effect, delivered potent antagonists devoid of BRD4 binding and of anti-proliferative activity. These compounds potently inhibited TLR7/8-mediated IL-6 production in human whole blood, with 9a giving IC50 values of 9.4 and 1.3 nM against TLR7 and TLR8, respectively. This orally bioavailable lead dose-dependently suppressed TLR7-mediated IL-6 and IFNα release in a mouse pharmacodynamic model.
Abstract The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway plays a pivotal role in host defense against pathogenic microbes and tumors. However, aberrant activation of this pathway is tightly associated with a wide spectrum of inflammatory and autoimmune disorders, positioning STING inhibition as a promising therapeutic strategy. In this study, we designed and synthesized a series of novel 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine derivatives as STING inhibitors. Compound 37 displayed potent STING inhibitory activity and favorable in vivo pharmacokinetic properties and safety. Further studies revealed that 37 blocks STING palmitoylation, thereby suppressing downstream signaling pathway activation. Oral administration of 37 exhibited significant anti-inflammatory effects in 10-carboxymethyl-9-acridanone (CMA)-challenged mice, Trex1−/− mice and cisplatin-induced acute kidney injury (AKI) mice. Collectively, compound 37 represents a novel orally bioavailable STING inhibitor with therapeutic potential against STING-driven inflammatory and autoimmune diseases.
Abstract A library of 1H-pyrrolo[3,2-c]quinolines (PQs) was synthesized, and SAR analysis identified compounds with low-nanomolar potency in CCRF-CEM cells (IC50 = 13−18 nM) and selectivity indices > 1000-fold over BJ fibroblasts. The most active derivatives retained activity against daunorubicin-resistant and paclitaxel-resistant sublines, indicating limited cross-resistance, and compounds 4, 14, and 17 showed efflux ratios < 2 in MDR1-MDCK and Caco-2 assays. Colchicine-site engagement was supported by various assays and docking/MD simulations. ADME profiling showed high chemical and plasma stability, plasma protein binding, and moderate-to-high microsomal clearance. After i.p. dosing in CD-1 mice at 12 mg/kg, compound 17 reached a maximum plasma concentration (Cmax) of 879.9 ng/mL (2.73 μM) at tmax = 15 min, with a 103 min half-life and limited brain penetration. In zebrafish embryos, 17 induced concentration-dependent developmental abnormalities (LC50 = 198 nM at 96 hpf), consistent with antimitotic activity but pointing to a narrow therapeutic window.
Abstract Idiopathic pulmonary fibrosis (IPF) remains a progressive and fatal lung disease with a substantial unmet need for safe and effective therapies. Highly selective inhibition of phosphodiesterase 4B (PDE4B) represents a promising therapeutic strategy for IPF while avoiding nausea and vomiting associated with PDE4D inhibition. However, achieving pronounced subtype selectivity remains particularly challenging; notably, the only approved PDE4B-preferential inhibitor, nerandomilast, exhibits only approximately 9-fold selectivity for PDE4B over PDE4D. Herein, we report the identification of YKS-34, a potent PDE4B inhibitor (IC50 = 1.71 nM) exhibiting >1000-fold selectivity over PDE4A, PDE4C, and PDE4D. YKS-34 effectively suppressed TGF-β-induced fibroblast activation and LPS-induced TNF-α release in vitro. In vivo, YKS-34 showed favorable pharmacokinetic properties, lung tissue accumulation, and reduced emetic potential at tested conditions while dose-dependently improving pulmonary dysfunction and fibrotic remodeling in a bleomycin-induced IPF mouse model. Consequently, YKS-34 emerges as a highly promising, next-generation candidate for the treatment of IPF.
Abstract Threonine tyrosine kinase (TTK), a core component of the spindle assembly checkpoint, plays an essential role in mitosis, and its inhibition has emerged as a promising therapeutic strategy for human cancers. We previously reported multiple approaches to target TTK, including reversible inhibitors, covalent inhibitors, and PROTAC degraders. In this study, we advance these efforts by developing a novel monovalent degrader of TTK. The representative compound, 26, generated by appending an electrophilic monomethyl fumarate handle to a TTK inhibitor, effectively induced TTK degradation and demonstrated superior antiproliferative activity across diverse cancer cell lines. Mechanistic investigations suggested that compound 26 primarily engages RNF126 and stabilizes its association with TTK, thereby inducing TTK ubiquitination and subsequent proteasomal degradation. Collectively, this work provides the first example of a TTK molecular glue-like degrader and introduces a new electrophilic handle for the rational design of degraders with reduced nonspecific cytotoxicity.
