Kirsty Houslay(1), Peter Bunyard(1), Kay Eckersley(1), Adriana Gambardella(1), Clifford Jones(1), Andrew Belfield(1), Diana Bishop(1), Helen McKeever(1), Helen Timmis(1), Jane Robertson(1), Richard Armer(1), Simon Bos(2), Debby Laukens(2)

Affiliates

(1)Redx Pharma PLC, UK, (2)University of Ghent, Belgium

Abstract

Introduction:
RXC008 is a potent and selective ROCK inhibitor with potential as a future treatment for fibrotic stricture formation in Crohn’s disease patients. ROCK is a key signalling kinase in fibrosis and suppression of ROCK activity is highly efficacious in multiple rodent models of fibrosis. Systemic inhibition of ROCK leads to unacceptable hypotension, therefore RXC008 has been designed to remain restricted to the GI with minimal systemic exposure.
Methods:
RXC008 was tested against ROCK1 and ROCK2 isolated enzymes and profiled in a phospho-MYPT1 (Myosin phosphatase Target Subunit 1) cell assay to establish mechanistic potency. The phenotypic effect of ROCK inhibition was evaluated by examining suppression of TGFβ (Transforming Growth Factor) stimulated alpha smooth muscle actin (α-SMA) in human intestinal fibroblasts (HIFs). In vivo efficacy for anti-fibrotic effect was determined in 45-day adoptive T-cell transfer (AT) and 9-week chronic dextran sulphate sodium (DSS) murine models of colitis.
Results:
RXC008 inhibited ROCK1 and ROCK2 with nanomolar potency and exhibited sub-micromolar potency against phospho-MYPT1 and α-SMA expression. In both in vivo fibrosis models RXC008 was dosed orally at 10 mg/kg once a day. In the 45-day AT model RXC008 was able to strongly suppress fibrosis and attenuate villi erosion and ulceration. Mechanism of action and biomarker studies in the DSS model demonstrated that RXC008 dosed for the duration of the study could also suppress fibrosis and reduce gene expression of fibrotic markers such as Col1a1, Col1a2 and TGFβ and increased the expression of markers associated with mucosal healing. Non-invasive magnetic resonance imaging (MRI) was also utilized to examine the extent of injury and fibrosis. RXC008 demonstrated a robust protective effect on both parameters that correlated with the histopathology scoring. No systemic exposure of RXC008 could be detected in either model despite sufficient GI tissue exposure.
Conclusions:
The data indicate that RXC008 can suppress fibrosis and attenuate tissue injury in animal models of Crohn’s disease and has the potential to be developed as a novel therapy to inhibit fibrotic stricture formation in Crohn’s disease. IND enabling activities are progressing with the aim to commence a first-in-human clinical trial in 2023.