Organic anion transporting polypeptide 2B1 (OATP2B1), an expanded substrate profile, does it align with OATP2B1's hypothesized function?

An expanded view of the substrate landscape of organic anion transporting polypeptide (OATP) 2B1 was pursued with the goal of understanding if the identification of novel in vitro substrates could shed additional light on the impact of OATP2B1 on intestinal absorption and brain penetration. To examine this hypothesis, a series of experiments measured the cellular accumulation of a diverse array of compounds. Representative angiotensin II receptor blockers (ARBs) and other compounds of interest were subsequently investigated for inhibition, time dependence, and kinetics. The study identified ARBs as a class of OATP2B1 substrates and found balsalazide, olsalzine, and gavestinel to be novel substrates of OATP2B1 too. Some compounds previously reported to be OATP2B1 substrates in the literature, aliskiren, erlotinib, montelukast, fexofenadine, and taurocholate could not be confirmed as substrates. Literature describing in vivo outcomes for OATP2B1 substrates, coproporphyrin III, ARBs, balsalazide, olsalzine, and gavestinel highlight the absence of a substantial impact of OATP2B1 on the oral absorption and/or brain penetration of OATP2B1 substrates. Suggestions of including OATP2B1 assessment as part of the drug approval process are likely premature and further mechanistic work with more robust OATP2B1 substrates, which may include some of those described here, is desirable.