A randomized, double-blind phase 1b study evaluating the safety, tolerability, pharmacokinetics and pharmacodynamics of the NLRP3 inhibitor selnoflast in patients with moderate to severe active ulcerative colitis

Abstract

Background: The NLRP3 inflammasome drives release of pro-inflammatory cytokines including interleukin (IL)-1β and IL-18 and is a potential target for ulcerative colitis (UC). Selnoflast (RO7486967) is an orally active, potent, selective and reversible small molecule NLRP3 inhibitor. We conducted a randomized, placebo-controlled Phase 1b study to assess the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of selnoflast.

Methods: Nineteen adults with previous diagnosis of UC and current active moderate to severe disease were randomized 2:1 to selnoflast or placebo for 7 days. A dose of 450 mg QD (once daily) was selected to achieve 90% IL-1β inhibition in plasma and colon tissue. Consecutive blood, sigmoid colon biopsies and stool samples were analyzed for a variety of PD markers. Safety and PK were also evaluated.

Results: Selnoflast was well-tolerated. Plasma concentrations increased rapidly after oral administration, reaching T_max 1 h post-dose. Mean plasma concentrations stayed above the IL-1β IC₉₀ level throughout the dosing interval (mean C_trough on Day 1 and Day 5: 2.55 μg/mL and 2.66 μg/mL, respectively). At steady state, post-dose selnoflast concentrations in sigmoid colon (5-20 μg/g) were above the IC₉₀ . Production of IL-1β was reduced in whole blood following ex vivo stimulation with lipopolysaccharide (LPS) (in the selnoflast arm). No changes were observed in plasma IL-18 levels. There were no meaningful differences in the expression of an IL-1-related gene signature in sigmoid colon tissue, and no differences in the expression of stool biomarkers.

Conclusions: Selnoflast was safe and well-tolerated. Selnoflast 450 mg QD achieved plasma and tissue exposure predicted to maintain IL-1β IC₉₀ over the dosing interval. However, PD biomarker results showed no robust differences between treatment arms, suggesting no major therapeutic effects are to be expected in UC. The limitations of this study are its small sample size and indirect assessment of the effect on IL-1β in tissue.

Trial registration: ISRCTN16847938.

Keywords: NLRP3 inflammasome; NLRP3 inhibitor; biomarker; inflammatory bowel disease; interleukin-1β; pharmacokinetics; phase 1b; safety; ulcerative colitis.

FIGURE 1

Flow chart of patient disposition.

FIGURE 2

Selnoflast plasma concentrations (mean ± SD) versus time. Treatment showed a rapid increase and limited accumulation over 7 days. Steady state was achieved on Day 2. The inter‐patient variability was low to moderate. Mean plasma concentrations remained above the IC₉₀ at trough.

FIGURE 3

Concentration of selnoflast in sigmoid colon mucosal tissue. Selnoflast concentrations were measured in sigmoid colon biopsies from individual patients, taken 2–4.5 h post‐dose on Day 7. The dotted line represents the tissue IC₉₀ value.

FIGURE 4

Inhibition of IL‐1β release in whole blood upon ex vivo stimulation with LPS. BL, baseline; d, days. Blood samples were obtained from patients treated with either placebo or selnoflast, at various timepoints pre‐ and post‐dosing. Blood samples were treated with LPS for 24 h prior to measurement of IL‐1β levels (in the supernatants). The level of IL‐1β is expressed as the percentage change from baseline (pre‐dose), including standard error bars.

FIGURE 5

Effect of selnoflast on markers of inflammation in blood, sigmoid colon tissue and stool. The graph depicts the log₂ fold change from baseline to Day 7 (± 95% confidence interval) in various inflammation markers measured in blood, sigmoid colon tissue and stool.

FIGURE 6

Expression of an IL‐1 gene signature in sigmoid colon tissue. RNA was extracted from sigmoid colon tissue samples that were obtained before treatment and on Day 7 to evaluate the expression of an IL‐1 gene signature by quantitative Polymerase Chain Reaction. The gene signature consisted of a panel of 8 genes: CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CCL2, IL6 and TNFAIP6. The graph depicts the log₂ fold change from baseline to Day 7 using a Box and Whisker Plot. Minimum, lower quartile, median, upper quartile and maximum are shown. The dots represent single samples. There was a slight decrease between baseline and Day 7 in the selnoflast arm, compared to the placebo arm.

FIGURE 7

Cell types detected by single cell RNA sequencing and changed expression of IL‐1 signature genes. (A) Uniform manifold approximation and projection (UMAP) plot of single‐cell data. Each dot represents one cell. Cells with similar gene expression profiles are clustered by the Leiden algorithm implemented in the scanpy software package.¹ Cell‐type annotation was performed with gene signatures provided by the BESCA software² and with manual curation. (B) Enrichment of genes that are induced by IL‐1 (abbreviated as ‘IL‐1 signature genes’ thereafter), stratified by treatment, cell type, and time points of sampling. The IL‐1 signature genes are curated from previous studies and include well‐established targets of IL‐1 such as IL6, CXCL2, CXCL3, CLCL5 and CCL2. Enrichment is quantified with the BioQC software.³ Higher BioQC scores indicate that the IL‐1 signature genes are more positively enriched in the gene expression of the sample. The plot visualizes only cell types in which the difference between placebo and treatment groups is the strongest, with unadjusted p‐values of Student's t‐test less than 0.10. ¹Wolf FA, Angerer P, Theis FJ. SCANPY: large‐scale single‐cell gene expression data analysis. Genome Biology 2018;19(1):15. ² Mädler SC, Julien‐Laferriere A, Wyss L, et al. Besca, a single‐cell transcriptomics analysis toolkit to accelerate translational research. NAR Genomics and Bioinformatics 2021;3(4):https://doi.org/10.1093/nargab/lqab102. ³Zhang JD, Hatje K, Sturm G, et al. Detect tissue heterogeneity in gene expression data with BioQC. BMC Genomics 2017;18(1):277.