Cereblon-based Bifunctional Degrader of SOS1, BTX-6654, Targets Multiple KRAS Mutations and Inhibits Tumor Growth.

Mutations within the oncogene KRAS drive an estimated 25% of all cancers. Only allele-specific KRAS G12C inhibitors are currently available and are associated with the emergence of acquired resistance, partly due to upstream pathway reactivation. Given its upstream role in the activation of KRAS, son of sevenless homolog 1 (SOS1), has emerged as an attractive therapeutic target. Agents that target SOS1 for degradation could represent a potential pan-KRAS modality that may be capable of circumventing certain acquired resistance mechanisms. Here, we report the development of two SOS1 cereblon-based bifunctional degraders, BTX-6654 and BTX-7312, cereblon-based bifunctional SOS1 degraders. Both compounds exhibited potent target-dependent and -specific SOS1 degradation. BTX-6654 and BTX-7312 reduced downstream signaling markers, pERK and pS6, and displayed antiproliferative activity in cells harboring various KRAS mutations. In two KRAS G12C xenograft models, BTX-6654 degraded SOS1 in a dose-dependent manner correlating with tumor growth inhibition, additionally exhibiting synergy with KRAS and MEK inhibitors. Altogether, BTX-6654 provided preclinical proof of concept for single-agent and combination use of bifunctional SOS1 degraders in KRAS-driven cancers.

CCX559 is a potent, orally-administered small molecule PD-L1 inhibitor that induces anti-tumor immunity.

The interaction of PD-L1 with PD-1 is a major immune checkpoint that limits effector T cell function against cancer cells; monoclonal antibodies that block this pathway have been approved in multiple tumor indications. As a next generation therapy, small molecule inhibitors of PD-L1 have inherent drug properties that may be advantageous for certain patient populations compared to antibody therapies. In this report we present the pharmacology of the orally-available, small molecule PD-L1 inhibitor CCX559 for cancer immunotherapy. CCX559 potently and selectively inhibited PD-L1 binding to PD-1 and CD80 in vitro, and increased activation of primary human T cells in a T cell receptor-dependent fashion. Oral administration of CCX559 demonstrated anti-tumor activity similar to an anti-human PD-L1 antibody in two murine tumor models. Treatment of cells with CCX559 induced PD-L1 dimer formation and internalization, which prevented interaction with PD-1. Cell surface PD-L1 expression recovered in MC38 tumors upon CCX559 clearance post dosing. In a cynomolgus monkey pharmacodynamic study, CCX559 increased plasma levels of soluble PD-L1. These results support the clinical development of CCX559 for solid tumors; CCX559 is currently in a Phase 1, first in patient, multicenter, open-label, dose-escalation study (ACTRN12621001342808).

Efficacy of Chemokine Receptor Inhibition in Treating IL-36α-Induced Psoriasiform Inflammation.

Several types of psoriasiform dermatitis are associated with increased IL-36 cytokine activity in the skin. A rare, but severe, psoriasis-like disorder, generalized pustular psoriasis (GPP), is linked to loss-of-function mutations in the gene encoding IL-36RA, an important negative regulator of IL-36 signaling. To understand the effects of IL-36 dysregulation in a mouse model, we studied skin inflammation induced by intradermal injections of preactivated IL-36α. We found the immune cells infiltrating IL-36α-injected mouse skin to be of dramatically different composition than those infiltrating imiquimod-treated skin. The IL-36α-induced leukocyte population comprised nearly equal numbers of CD4+ αß T cells, neutrophils, and inflammatory dendritic cells, whereas the imiquimod-induced population comprised γδ T cells and neutrophils. Ligands for chemokine receptors CCR6 and CXCR2 are increased in both GPP and IL-36α-treated skin, which led us to test an optimized small-molecule antagonist (CCX624) targeting CCR6 and CXCR2 in the IL-36α model. CCX624 significantly reduced the T cell, neutrophil, and inflammatory dendritic cell infiltrates and was more effective than saturating levels of an anti-IL-17RA mAb at reducing inflammatory symptoms. These findings put CCR6 and CXCR2 forward as novel targets for a mechanistically distinct therapeutic approach for inflammatory skin diseases involving dysregulated IL-36 signaling, such as GPP.

Synthesis and biological evaluation of a series of liver-selective phosphonic acid thyroid hormone receptor agonists and their prodrugs.

Phosphonic acid (PA) thyroid hormone receptor (TR) agonists were synthesized to exploit the poor distribution of PA-based drugs to extrahepatic tissues and thereby to improve the therapeutic index. Nine PAs showed excellent TR binding affinities (TRbeta(1), K(i) < 10 nM), and most of them demonstrated significant cholesterol lowering effects in a cholesterol-fed rat (CFR) model. Unlike the corresponding carboxylic acid analogue and T(3), PA 22c demonstrated liver-selective effects by inducing maximal mitochondrial glycerol-3-phosphate dehydrogenase activity in rat liver while having no effect in the heart. Because of the low oral bioavailability of PA 22c, a series of prodrugs was synthesized and screened for oral efficacy in the CFR assay. The liver-activated cyclic 1-(3-chlorophenyl)-1,3-propanyl prodrug (MB07811) showed potent lipid lowering activity in the CFR (ED(50) 0.4 mg/kg, po) and good oral bioavailability (40%, rat) and was selected for development for the treatment of hypercholesterolemia.