The paper is focusing on tepotinib, a novel c-MET tyrosine kinase inhibitor approved in February 2021 by FDA for the treatment of NSCLC. In the study, we aimed to characterize its potential to act as a modulator of pharmacokinetic cytostatic resistance and perpetrator of drug interactions. In accumulation studies, tepotinib exhibited potent inhibition of ABCB1 and ABCG2, while only moderate interaction was recorded for ABCC1 efflux transporter. In addition, tepotinib inhibited several recombinant cytochrome P450 (CYP) isoforms with differing potency. Furthermore, tepotinib synergistically reversed daunorubicin and mitoxantrone resistance in ex vivo explants derived from NSCLC patients with ABCB1 and ABCG2 overexpression, thus we demonstrated that tepotinib modulates MDR in patient-derived NSCLC explants, confirming its clinical chemosensitizing potential. Tepotinib was designated as ABCB1 substrate in monolayer transport assays, but the functional presence of the transporter had no significant influence on the anticancer effect. In conclusion, the drug might be potentially utilized as a valuable chemosensitizer in patients suffering from NSCLC tumors expressing ABCB1 and/or ABCG2. This GAUK project covered the ex vivo transporter part of the paper.

Encorafenib (LGX818, trade name Braftovi), a novel BRAF inhibitor, has been approved for the treatment of melanoma and colorectal cancer. Next to its primary indication, the drug is a promising candidate for NSCLC therapy. In the paper, we evaluated encorafenib’s possible antagonistic effect on pharmacokinetic mechanisms of multidrug resistance (MDR) as well as its perpetrator role in drug interactions. Firstly, encorafenib potently inhibited the efflux function of ABCC1 transporter in drug accumulation assays, while moderate and null interaction levels were recorded for ABCB1 and ABCG2, respectively. In contrast, the mRNA expression levels of all the tested transporters were not altered by encorafenib. In the drug combination studies, we found that daunorubicin and topotecan resistances were synergistically attenuated by the encorafenib-mediated interaction in A431-ABCC1 cells. Noteworthy, further experiments in ex vivo patients-derived explants confirmed the MDR-modulating ability of encorafenib. Advantageously, overexpression of tested drug efflux transporters failed to hinder the antiproliferative activity of encorafenib. In addition, no significant modulation of CYP3A4 enzyme’s activity by encorafenib was observed. In conclusion, our work indicated that encorafenib can act as an effective chemosensitizer targeting the ABCC1-induced MDR. Our in vitro and ex vivo data might provide a valuable information for designing the novel effective scheme applicable in the clinical pharmacotherapy of BRAF-mutated/ABCC1-expressing tumors. This GAUK project covered the ex vivo part of the paper.

ATP-binding cassette (ABC) drug efflux transporters and drug metabolizing enzymes play a crucial roles in pharmacokinetic drug-drug interactions and multidrug tumor resistance (MDR). Tazemetostat (EPZ-6438, Tazverik) is a novel epigenetic drug that has been recently approved for the therapy of advanced epithelioid sarcoma and follicular lymphoma. Additionally, this medication is currently being clinically tested to treat several other cancers such as non-small cell lung cancer (NSCLC). This study aimed to investigate the inhibitory effects of tazemetostat on selected ABC transporters/cytochrome P450 3A4 (CYP3A4) enzyme and to comprehensively explore its role in MDR. First, our accumulation and molecular docking studies showed that tazemetostat is a unique triple inhibitor of ABCB1, ABCC1, and ABCG2 transporters. In contrast, tazemetostat exhibited only low level of interaction with the CYP3A4 isozyme. Drug combination assays confirmed that tazemetostat is a multipotent MDR modulator able to synergize with various conventional chemotherapeutics in vitro. Subsequent caspase activity assays and microscopic staining of apoptotic nuclei proved that the effective induction of apoptosis is behind the observed synergies. Notably, a potent MDR-modulatory capacity of tazemetostat was recorded in primary ex vivo NSCLC explants generated from patients’ biopsies. On the contrary, its possible position of pharmacokinetic MDR’s victim was excluded in comparative proliferation assays. Finally, tested drug has not been identified as an inducer of resistant phenotype in NSCLC cell lines. In conclusion, we demonstrated that tazemetostat is as a unique multispecific chemosensitizer, which has strong potential to overcome limitations seen in the era of traditional MDR modulators.