Metabolism of JQ1, an inhibitor of bromodomain and extra terminal bromodomain proteins, in human and mouse liver microsomes†

Abstract

JQ1 is a small-molecule inhibitor of the bromodomain and extra terminal (BET) protein family that potently inhibits the bromodomain testis-specific protein (BRDT), which is essential for spermatogenesis. JQ1 treatment produces a reversible contraceptive effect by targeting the activity of BRDT in mouse male germ cells, validating BRDT as a male contraceptive target. Although JQ1 possesses favourable physical properties, it exhibits a short half-life. Because the details of xenobiotic metabolism play important roles in the optimization of drug candidates and in determining the role of metabolism in drug efficacy, we investigated the metabolism of JQ1 in human and mouse liver microsomes. We present the first comprehensive view of JQ1 metabolism in liver microsomes, distinguishing nine JQ1 metabolites, including three monohydroxylated, one de-tert-butylated, two dihydroxylated, one monohydroxylated/dehydrogenated, one monohydroxylated-de-tert-butylated and one dihydroxylated/dehydrogenated variant of JQ1. The dominant metabolite (M1) in both human and mouse liver microsomes is monohydroxylated on the fused three-ring core. Using recombinant cytochrome P450 (CYP) enzymes, chemical inhibitors and the liver S9 fraction of Cyp3a-null mice, we identify enzymes that contribute to the formation of these metabolites. Cytochrome P450 family 3 subfamily A member 4 (CYP3A4) is the main contributor to the production of JQ1 metabolites in vitro, and the CYP3A4/5 inhibitor ketoconazole strongly inhibits JQ1 metabolism in both human and mouse liver microsomes. Our findings suggest that JQ1 half-life and efficacy might be improved in vivo by co-administration of a selective CYP inhibitor, thereby impacting the use of JQ1 as a probe for BRDT activity in spermatogenesis and as a probe or therapeutic in other systems.

Inhibitors of bromodomain and extra‐terminal proteins for treating multiple human diseases

“…57,58,[158][159][160] For example, JQ1 has been proposed as a treatment for NUT-midline carcinoma because this disease stems from an oncoprotein arising from the fusion of BRD4 to NUT. 54,58,61,[161][162][163] Unfortunately, JQ1 is not a clinical candidate due to unfavorable pharmacokinetic properties, 164 however, many other noncovalent BETi are being clinically evaluated for the treatment of cancer and cardiovascular disease. 52,59,…”

Synergistic efficacy of inhibiting MYCN and mTOR signaling against neuroblastoma

“…In this study, we used JQ1, a potent preclinical BET protein inhibitor, as a proof of concept for targeting MYCN transcription [ 16 ]. Since JQ1 is not being tested in clinical trials due to its short half-life [ 28 ], in parallel, we used the clinically relevant BET protein inhibitor OTX-015 as an alternative agent to target MYCN. We confirmed that JQ1 and OTX-015 have similar anti-NB efficacy in our proof-of-concept study.…”

Inhibition of drug-metabolizing enzymes by Qingfei Paidu decoction: Implication of herb-drug interactions in COVID-19 pharmacotherapy

“…P450 inhibition experiments were carried out in 200 μL reaction mixtures, which included potassium phosphate buffer (PBS, 100 mM, pH 7.4), each P450 substrate, NADPH-generating system (10 mM G-6-P, 1.0 unit/mL G-6-PDH, 1.0 mM β-NADP + and 4.0 mM MgCl 2 , HLMs or RLMs, along with inhibitor ( Li et al, 2020b ; Santori et al, 2020 ; Salerno et al, 2020 ; Fang et al, 2020 ; Zhang et al, 2020b ). Each P450 substrate and the details of P450 reactions are shown in Table S2 .…”