Preincubation of a drug uptake transporter with its inhibitor in a cell-based assay may result in the apparent enhancement of the inhibitory potency. Limited data is available on whether this potentiation of transporter inhibition by preincubation (PTIP) takes place with clinically relevant solute-carrier transporters other than OATP1B1/3. Therefore, PTIP was examined systematically using OATP1B1/3, OAT1/3, OCT1/2, and MATE1/2-K cell lines. IC₅₀ values were determined with or without 3 hours of preincubation, and compounds with a PTIP ≥2.5x were further characterised by assessing the time course of transport inhibition potency and cellular concentration. The extent of potentiation was correlated with the physicochemical properties of individual inhibitors. PTIP was observed for OCTs as well as OATPs but not for OATs or MATEs, and most instances of PTIP persisted after controlling for toxicity and non-specific binding. In certain cases, preincubation in excess of 2 hours was required to attain full inhibitory potency. For 5/30 drugs examined, preincubation had the potential to change the in vitro drug-drug interaction risk prediction from "no risk" to "risk" based on current regulatory criteria. Molecular weight and LogD7.4, as well as the ratio of passive cellular accumulation and cellular uptake rate (K_p,passive/PS_inf) correlated with PTIP; thus, low cellular permeation and a slow build-up of unbound intracellular inhibitor concentration may contribute to PTIP. Taken together, our data suggest that PTIP is partly determined by the physicochemical properties of the perpetrator drug, and preincubation may affect the in vitro predicted DDI risk for OCTs as well as OATPs. SIGNIFICANCE STATEMENT During the development of a novel pharmaceutical drug, in vitro studies are conducted to assess the risk of potential adverse interactions between existing medications a patient may already be taking and the novel compound. The exact way these in vitro assays are performed may influence the outcome of risk assessment. Here we suggest that the interaction risk may be underestimated unless specific assay protocols are modified to include an additional incubation step that allows the test drug to accumulate inside the cells, and demonstrate that adding this step is particularly important for large and hydrophobic drug molecules.

Asciminib is a first-in-class allosteric inhibitor of the kinase activity of BCR::ABL1, specifically targeting the ABL myristoyl pocket (STAMP). This review focuses on the pharmacokinetic (PK) and pharmacodynamic data of asciminib, which is approved at a total daily dose of 80 mg for the treatment of adult patients with chronic myeloid leukemia in chronic phase who are either resistant or intolerant to ≥ 2 tyrosine kinase inhibitors or those harboring the T315I mutation (at a dose of 200 mg twice daily). Asciminib is predicted to be almost completely absorbed from the gut, with an absolute bioavailability (F) of approximately 73%. It should be administered in a fasted state, as food (particularly high-fat meals) reduces exposure. Asciminib displays a slightly greater than dose-proportional increase in exposure, with no time-dependent changes in PK observed following repeated dosing. This drug shows low clearance (6.31 L/h), with a moderate volume of distribution (111 L) and high human plasma protein binding (97.3%). The apparent terminal elimination half-life (t_1/2) across studies was estimated to be between 7 and 15 h. The PK of asciminib is not substantially affected by body weight, age, gender, race, or renal or hepatic impairment. Asciminib is primarily metabolized via CYP3A4-mediated oxidation (36.0%) and UGT2B7- and UGT2B17-mediated glucuronidation (13.3% and 7.8%, respectively); biliary secretion via breast cancer resistance protein contributes to about 31.1% to total systemic clearance, which is mainly through hepatic metabolism and biliary secretion through the fecal pathway, with renal excretion playing a minor role. The potential for PK drug interaction for asciminib both as a victim and a perpetrator has been summarized here based on clinical and predicted drug–drug interaction studies. Robust exposure–response models characterized asciminib exposure–efficacy and exposure–safety relationships. In patients without the T315I mutation, the exposure–efficacy analysis of the time course of BCR::ABL1^IS percentages highlighted the existence of a slightly positive, albeit not clinically significant, relationship. Higher exposure was required for efficacy in patients harboring the T315I mutation compared with those who did not. The exposure–safety relationship analysis showed no apparent association between exposure and adverse events of interest over the broad range of exposure or dose levels investigated. Asciminib has also been shown to have no clinically relevant effect on cardiac repolarization. Here, we review the clinical pharmacology data available to date for asciminib that supported its clinical development program and regulatory applications.

We predicted the drug–drug interaction (DDI) potential of siponimod in presence of cytochrome P450 (CYP)2C9/CYP3A4 inhibitors/inducers in subjects with different CYP2C9 genotypes by physiologically‐based pharmacokinetic (PK) modeling. The model was established using in vitro and clinical PK data and verified by adequately predicting siponimod PK when coadministered with rifampin. With strong and moderate CYP3A4 inhibitors, an increased DDI risk for siponimod was predicted for CYP2C9*3/*3 genotype vs. other genotypes area under the curve ratio (AUCR): 3.03–4.20 vs. ≤ 1.49 for strong; 2.42 vs. 1.14–1.30 for moderate. AUCRs increased with moderate (2.13–2.49) and weak (1.12–1.42) CYP3A4/CYP2C9 inhibitors to the same extent for all genotypes. With strong CYP3A4/moderate CYP2C9 inducers and moderate CYP3A4 inducers, predicted AUCRs were 0.21–0.32 and 0.35–0.71, respectively. This complementary analysis to the clinical PK‐DDI studies confirmed the relevant influence of CYP2C9 polymorphism on the DDI behavior of siponimod and represented the basis for the DDI labeling recommendations.