In vitro safety evaluation of dopamine D3R antagonist, R-VK4-116, as a potential medication for the treatment of opioid use disorder.

R-VK4-116 is currently being developed as a medication to treat opioid use disorder (OUD). To characterize in vitro safety properties of R-VK4-116, metabolic stability in hepatocytes or liver microsomes, metabolite identification, metabolism/transporter-mediated drug interactions, lysosomal perturbation, mitochondrial toxicity, off-target enzyme effects, cellular and nuclear receptor functional assays, electrophysiological assays, CiPA, KINOMEscanTM, plasma protein binding, phospholipidosis and steatosis assays were performed. Overall, R-VK4-116 was metabolically stable in hepatocytes and microsomes. Four major metabolites were detected: two mono-oxidation products, one di-oxidation product, and one demethylated plus di-oxidation product. CYP2D6 and CYP3A4 were major contributors in R-VK4-116 metabolism. Further, R-VK4-116 did not induce/inhibit CYP enzymes. However, R-VK4-116 inhibited BCRP/P-gp, and showed antagonist effects on α1A(h), H1(h) and agonist effect on hGABAA∞1β2γ2 at 10 μM. R-VK4-116 inhibited hERG and Kir2.1 at a high concentration of 100 μM. KINOMEscanTM provided 5 hits (CHEK2, HPK1, MARK3, SRPK2 and TNK1) with Kds of >10 μM. Further, R-VK4-116 was bound to human, rat and dog plasma proteins (~83-93%). R-VK4-116 did not induce lysosome perturbation, mitochondrial toxicity, phospholipidosis, or steatosis at ≤10 μM. These results demonstrated that R-VK4-116 possesses favorable in vitro safety properties and supports further development as a potential medication for OUD.