Adagrasib, a KRAS G12C inhibitor, reverses the multidrug resistance mediated by ABCB1 in vitro and in vivo

Background: Multidrug resistance (MDR) is a complex phenomenon that frequently leads to chemotherapy failure during Cancer treatment. The overexpression of ATP-binding cassette (ABC) transporters represents the major mechanism contributing to MDR. To date, no effective MDR modulator has been applied in clinic. Adagrasib (MRTX849), a specific inhibitor targeting KRAS G12C mutant, is currently under investigation in clinical trials for the treatment of non-small cell lung Cancer (NSCLC). This study focused on investigating the circumvention of MDR by MRTX849.

Methods: The cytotoxicity and MDR reversal effect of MRTX849 were assessed by MTT assay. Drug accumulation and drug efflux were evaluated by flow cytometry. The MDR reversal by MRTX849 in vivo was investigated in two ABCB1-overexpressing tumor xenograft models in nude mice. The interaction between MRTX849 and ABCB1 substrate binding sites was studied by the [¹²⁵I]-IAAP-photoaffinity labeling assay. The vanadate-sensitive ATPase assay was performed to identify whether MRTX849 would change ABCB1 ATPase activity. The effect of MRTX849 on expression of ABCB1 and PI3K/Akt signaling molecules was examined by flow cytometry, Western blot and Quantitative Real-Time PCR analyses.

Results: MRTX849 was shown to enhance the Anticancer efficacy of ABCB1 substrate drugs in the transporter-overexpressing cells both in vitro and in vivo. The MDR reversal effect was specific against ABCB1 because no similar effect was observed in the parental sensitive cells or in ABCG2-mediated MDR cells. Mechanistically, MRTX849 increased the cellular accumulation of ABCB1 substrates including doxorubicin (Dox) and rhodamine 123 (Rho123) in ABCB1-overexpressing MDR cells by suppressing ABCB1 efflux activity. Additionally, MRTX849 stimulated ABCB1 ATPase activity and competed with [^125I]-IAAP for photolabeling of ABCB1 in a concentration-dependent manner. However, MRTX849 did not alter ABCB1 expression or phosphorylation of Akt/ERK at the effective MDR reversal drug concentrations.

Conclusions: In summary, MRTX849 was found to overcome ABCB1-mediated MDR both in vitro and in vivo by specifically attenuating ABCB1 efflux activity in drug-resistant Cancer cells. Further studies are warranted to translate the combination of MRTX849 and conventional chemotherapy to clinical application for circumvention of MDR. Video Abstract.