(T1030-04-23) Clinical Potential of UK4b as a New Generation of Anti-Inflammatory Drug to Treat Pain and Arthritis

Purpose: Currently available non-steroid anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX)-1 and/or COX-2, all with significant cardiovascular, cerebrovascular, and gastrointestinal risks that have limited their clinical applications. Microsomal prostaglandin E2 (PGE₂ synthase 1 (mPGES-1), an inducible enzyme responsible for PGE₂ overproduction, is considered as a potentially more promising target for a new class of anti-inflammatory drug without the adverse effects associated with the COX-1/2 inhibition. There have been extensive efforts in drug design and discovery targeting mPGES-1. Unfortunately, within the previously reported potent human mPGES-1 inhibitors, few have been identified as also potent inhibitors of mouse or rat mPGES-1, which prevents the use of well-established mouse or rat models of inflammation and pain in preclinical drug development. We have recently designed and discovered a novel compound, denoted as UK4b, capable of potently inhibiting both human and mouse mPGES-1 by targeting the conserved region of the active site cavity.¹ In the present study, we further examined whether UK4b has the desired absorption, distribution, metabolism, and excretion (ADME) properties and safety as a drug candidate and whether oral administration of UK4b can significantly attenuate pain and arthritis

Methods: To examine the ADME properties, UK4b was submitted for the standard ADME assays via CRO services provided by Eurofins. The in vivo anti-inflammatory and analgesic effects of UK4b were examined in two rat models, including carrageenan-induced paw edema/hyperalgesia and Complete Freund’s Adjuvant (CFA)-induced knee joint arthritis when UK4b was administered to male Sprague-Dawley rats (n=10/group) via oral gavage (PO). In the CFA-induced knee joint arthritis model, CFA was injected into the knee joint on Day 0 and the treatment (UK4b or vehicle) was administered daily during Days 3-5; each animal was observed during Days 0-12 for the arthritis score. Further, UK4b was evaluated for broad off-target selectivity by CEREP of Eurofins using their CEREP SafetyScreen44 panel and for genetic toxicity by Eurofins using their Ames Fluctuation Test assays. Additional toxicity testing on UK4b was performed by using the SYSTEMETRIC^® Cell Health Screen by AsedaSciences^® to predict safety in humans as a drug candidate.

Results: ADME data obtained by Eurofins for UK4b using the ADME panel: (1) protein binding in human plasma – 8% with 86% recovery; (2) aqueous solubility – 177.3 mM (simulated gastric fluid) or 87.3 mM (simulated intestinal fluid); (3) LogD (n-octanol/PBS, pH 7.4) = 2.60; (4) permeability (Caco-2, pH 6.5/7.4; in 10^-6 cm/s) – 29.3 with 87% recovery (A-B) and 18.8 with 84% recovery (B-A); (5) intrinsic clearance (liver microsomes, human) – t_1/2 > 72 min and CL_int < 0.00963 μL/min/mg (compared to previously reported CL_int < 0.00776 μL/min/mg for celecoxib). These ADME properties suggest that UK4b is suitable for oral administration. Concerning the in vivo anti-inflammatory and analgesic effects, PO administration of UK4b significantly attenuated carrageenan-induced edema (reflected by the volume of the hind paw injected with carrageenan) and hyperalgesia (characterized by paw withdrawal latency or PWL) in rats. In the CFA-induced knee joint arthritis model, the arthritis score reached the highest on Day 3 and started to gradually decrease from Day 4 to Day 12. Compared to the vehicle control group, the UK4b treatment beginning Day 3 significantly and dose-dependently accelerated the decrease in the arthritis score. Concerning safety, according to the CEREP panel screen, UK4b was highly selective for mPGES-1 over all the off-targets. Within all these off-targets, the most active one for UK4b was COX-1 with IC₅₀ = 3.6 μM. So, UK4b has a ~110-fold selectivity for human mPGES-1 (IC₅₀ = 33 nM) over COX-1 (IC₅₀ = 3.6 mM) and even much higher selectivity over the other off-targets within the CEREP panel. The broad screening data supports that the analgesic effects of UK4b are due to inhibition of mPGES-1, instead of the other targets (GPCRs such as opioid receptors and CB1/CB2 receptors, ion channels, transporters etc.) within the CEREP panel used. The Ames Fluctuation Test by Eurofins favorably concluded that UK4b has no genetic toxicity at all. The SYSTEMETRIC^® Cell Health Screen by AsedaSciences^® resulted in a very favorable Cell Health Screen score of 0.15 for UK4b (better than most of the FDA-approved drugs used in comparison).

Conclusion: The ADME properties of UK4b are suitable for oral administration, and UK4b administered PO has the desired anti-inflammatory and analgesic effects in wild-type rats. The broad screening data (including those from the CEREP panel screen, Ames Test, and SYSTEMETRIC^® Cell Health screen) all favor UK4b as a potentially promising drug candidate.

References: 1. Ding, K.; Zhou, Z.; Hou, S.; Yuan, Y.; Zhou, S.; Zheng, X.; Loftin, C.; Zheng, F.; Zhan, C.-G., Structure-based discovery of mPGES-1 inhibitors suitable for preclinical testing in wild-type mice as a new generation of anti-inflammatory drugs. Sci. Rep. 2018, 8, 5205.

Acknowledgements: This work was supported in part by the U.S. Department of Defense (DOD) Chronic Pain Management Research Program (CPMRP) Investigator-Initiated Research Award W81XWH2211000 and the National Institutes of Health (NIH) grant U01 HL152392 (funded by NCI, NEI, NHGRI, NIDCR, the Commonwealth of Kentucky). There is no conflict of interest for this study.


Uk4b ADME


Uk4b toxicity