Pharmacodynamic Monitoring of RO5459072, a Small Molecule Inhibitor of Cathepsin S

Abstract

Major histocompatibility complex class II (MHCII)-restricted antigen priming of CD4+ T cells is both involved in adaptive immune responses and the pathogenesis of autoimmune diseases. Degradation of invariant chain Ii, a protein that prevents premature peptide loading, is a prerequisite for nascent MHCII–peptide complex formation. A key proteolytic step in this process is mediated by cathepsin S. Inhibition of this cysteine protease is known to result in the intracellular accumulation of Lip10 in B cells. Here, we describe the development and application of a neoepitope-based flow cytometry assay measuring accumulation of Lip10. This novel method enabled the investigation of cathepsin S-dependent MHCII maturation in professional antigen-presenting cell (APC) subsets. Inhibition of cathepsin S by a specific inhibitor, RO5459072, in human PBMC ex vivo resulted in accumulation of Lip10 in B cells and myeloid dendritic cells, but not in plasmacytoid dendritic cells and only to a minor degree in monocytes. We qualified Lip10 as a pharmacodynamic biomarker by showing the cathepsin S inhibitor-dependent accumulation of Lip10 in vivo in cynomolgus monkeys treated with RO5459072. Finally, dosing of RO5459072 in a first-in-human clinical study (, identifier NCT02295332) exhibited a dose-dependent increase in Lip10, confirming target engagement and demonstrating desired pharmacologic inhibition in vivo. The degree of cathepsin S antagonist-induced maximum Lip10 accumulation in APCs varied significantly between individuals both in vitro and in vivo. This finding has not been reported previously using alternative, less sensitive methods and demands further investigation as to the potential of this biomarker to predict response to treatment. These results will help guide subsequent clinical studies investigating the pharmacokinetic and pharmacodynamic relationship of cathepsin S inhibitor RO5459072 after multiple dosing.

Cathepsin S activation contributes to elevated CX3CL1 (fractalkine) levels in tears of a Sjögren’s syndrome murine model

“…Several CTSS inhibitors are in clinical trials for autoimmune diseases, including RWJ-445380 (www.clinicaltrials.gov, Identifier: NCT00425321) and RO5459072 (www.clinicaltrials.gov, Identifier: NCT02701985). These therapeutic studies have focused primarily on assessment of MHC II-related endpoints such as Iip10 accumulation or H2-Ab1 gene expression as indicators of therapeutic efficacy 49 . CX3CL1 levels and CX3CL1+ immune cell counts in tissues of interest may serve as additional endpoints for CTSS activity.…”

Inhibition of Cathepsin S Reduces Lacrimal Gland Inflammation and Increases Tear Flow in a Mouse Model of Sjögren’s Syndrome

“…LY3000328 (www.clinicaltrials.gov, Identifier: NCT01515358) is in phase I clinical trials for abdominal aortic aneurysm treatment 66 . RWJ-445380 (www.clinicaltrials.gov, Identifier: NCT00425321) and RO5459072 (www.clinicaltrials.gov, Identifier: NCT02701985) are in phase II trials for rheumatoid arthritis and SS, respectively 67,68 . This study validates a role for CTSS activity in autoimmune dacryoadenitis in a murine model with many similarities to human SS, suggesting it as a therapeutic target for the treatment of SS.…”

Increased Cathepsin S activity associated with decreased protease inhibitory capacity contributes to altered tear proteins in Sjögren’s Syndrome patients

“…In recent years, CTSS, with its many functions linked to inflammation, has been linked to the etiology of many autoimmune diseases. The clinical efficacy of CTSS inhibitors is currently under investigation in inflammatory disorders including RA, SLE, plaque psoriasis, and, more recently, SS, both in animal disease models 25 – 27 and in human clinical trials 28 , 29 . We have previously shown increased CTSS activity in tears of SS patients 5 , however, little is known about the basis for this increase or its impact on other tear components.…”