Pharmacokinetics and Safety Studies in Rodent Models Support Development of EPICERTIN as a Novel Topical Wound-Healing Biologic for Ulcerative Colitis.

Daniel Tusé,Goo Lee,Joshua Royal,Abhishek Trigunaite,Micaela Reeves,Hanna Ng,Krystal T Hamorsky,Carol Green,Toufan Parman,Maria Arolfo,Nobuyuki Matoba

doi:10.1124/jpet.121.000904

Abstract

The novel wound-healing biologic EPICERTIN, a recombinant analog of cholera toxin B subunit, is in early development for the management of ulcerative colitis. This study established for the first time the pharmacokinetics (PK), bioavailability (BA), and acute safety of EPICERTIN in healthy and dextran sodium sulfate-induced colitic mice and healthy rats. For PK and BA assessments, single administrations of various concentrations of EPICERTIN were given intravenously or intrarectally to healthy and colitic C57BL/6 mice and to healthy Sprague-Dawley rats. After intravenous administration to healthy animals, the drug's plasma half-life (t 1/2) for males and females was 0.26 and 0.3 hours in mice and 19.4 and 14.5 hours in rats, respectively. After intrarectal administration, drug was detected at very low levels in only four samples of mouse plasma, with no correlation to colon epithelial integrity. No drug was detected in rat plasma. A single intrarectal dose of 0.1 µM (0.6 µg/mouse) EPICERTIN significantly facilitated the healing of damaged colonic epithelium as determined by disease activity index and histopathological scoring, whereas 10-fold higher or lower concentrations showed no effect. For acute toxicity evaluation, healthy rats were given a single intrarectal administration of various doses of EPICERTIN with sacrifice on Day 8, recording body weight, morbidity, mortality, clinical pathology, and gross necropsy observations. There were no drug-related effects of toxicological significance. The no observed adverse effect level (intrarectal) in rats was determined to be 5 µM (307 µg/animal, or 5.2 µg drug/cm2 of colorectal surface area), which is 14 times the anticipated intrarectally delivered clinical dose. SIGNIFICANCE STATEMENT: EPICERTIN is a candidate wound-healing biologic for the management of ulcerative colitis. This study determined for the first time the intravenous and intrarectal pharmacokinetics and bioavailability of the drug in healthy and colitic mice and healthy rats, and its acute safety in a dose-escalation study in rats. An initial therapeutic dose in colitic mice was also established. EPICERTIN delivered intrarectally was minimally absorbed systemically, was well tolerated, and induced epithelial wound healing topically at a low dose.

Highlights

Topical mucosal administration of cholera toxin B subunit (CTB), such as via oral delivery or intrarectal enema, leads to broad-spectrum biological effects, including immunostimulatory effects as well as specific immunosuppressive effects against autoimmune disorders, excess inflammation, and allergic reactions (Baldauf et al, 2015; Royal and Matoba, 2017)
We previously reported that a recombinant CTB containing a C-terminal endoplasmic reticulum (ER) retention motif (CTBKDEL), but not native CTB, induces colon epithelial wound healing in colitis via the activation of an unfolded protein response (UPR) in colon epithelial cells (Royal et al, 2019a)
None of the treatment groups had a statistically significant difference in body weight recovery compared to the PBS group; on Days 11 and 12 the 0.1 and 0.01 μM groups began to trend toward an increase in body weight recovery (Figure 1A)

Summary

Introduction

Topical mucosal administration of cholera toxin B subunit (CTB), such as via oral delivery or intrarectal enema, leads to broad-spectrum biological effects, including immunostimulatory effects as well as specific immunosuppressive effects against autoimmune disorders, excess inflammation, and allergic reactions (Baldauf et al, 2015; Royal and Matoba, 2017). CTB-KDEL, named EPICERTIN (Epithelial Cell ER-Targeted Protein), exhibits unique wound healing effects in the colon that are mediated by its localization to the ER and subsequent activation of UPR in epithelial cells These results suggest EPICERTIN’s utility as a novel therapeutic for mucosal healing, which is a significant unmet need in the management of IBD. We report for the first time the pharmacokinetics (PK), bioavailability (BA) and acute safety of EPICERTIN in healthy and DSS-induced colitic mice and healthy (non-colitic) rats using single administrations of study drug at escalating dose levels The results of these initial studies encourage further development of EPICERTIN as a novel candidate biologic for the topical management of IBD, especially for ulcerative colitis (UC)

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