Abstract A027: Acceleration of drug metabolism mediated by CYP3A4 enzyme activation provides a bona fide environmental resistance mechanism to targeted therapies
Authors: Kumar Pragya , Velde Robert Vander , Weh Malgorzata , Marusyk Andriy 
Published: November 2024

Abstract
Background: Targeted therapies against oncogenic signaling addictions, including one resulting from EML4-ALK fusions, can induce strong and durable clinical responses. However, these therapies are not curative in advanced cancers, as a subset of tumor cells avoid elimination, and these persisting populations evolve resistance that drives tumor relapse. Using a drug screen, we found that the evolving ALK inhibitor (ALKi) persisters display exquisite sensitivity to the histone demethylase inhibitor, JIB04 in vitro. Paradoxically, validation studies in mice revealed that instead of enhancing tumor sensitivity, JIB04 desensitizes tumors to ALKi, alectinib and lorlatinib, suggesting that it activates an unknown environmental modifier. While JIB04 is not used in the clinics, we reasoned that deciphering the underlying mechanism could uncover environment-mediated resistance to ALKi that might be triggered by clinically relevant factors. Results: We found that the resistance-promoting effect of JIB04 in mice is mediated by reducing systemic ALKi concentrations. This reduction is attributable to accelerated pharmacokinetics, due to the hyperactivation of the P450 family member, CYP3A4. Higher CYP3A4 activity leads to faster drug clearance and reduced drug exposure to tumors. Importantly, JIB04 triggers a similar resistance to other clinically relevant CYP3A4 substrates, the frontline EGFR inhibitor, osimertinib and the recently introduced KRASG12C inhibitor, sotorasib. Finally, the resistance- promoting effects of JIB04 could be phenocopied by chemically unrelated activators of CYP3A4, indicating a wide generalizability of this macro-environmental therapy resistance mechanism. Conclusions: Our study uncovered that acceleration of drug metabolism, triggered by CYP3A4 enzyme activators is a bona fide environmental resistance mechanism. Since P450 family liver detoxifying enzymes mediate the metabolism of many drugs, this resistance mechanism is likely to be relevant to a broad range of therapeutic contexts. Significance: While the importance of pharmacokinetic considerations is widely appreciated, modulation of drug metabolism is not typically considered as a candidate mechanism when therapy resistance is encountered in research and clinical settings. Multiple dietary, pharmacological and genetic modifiers are known to modulate P450 family enzymes. Moreover, substantial variability in drug plasma concentrations was documented in patients treated with identical doses of targeted therapies, and this variability strongly correlated with variability in clinical responses. While the direct link between variability in CYP3A4 activity and clinical outcomes in human patients has yet to be established, the mechanism uncovered in our study might represent a substantial but entirely overlooked contributor to resistance. Consequently, consideration of this mechanism and monitoring of CYP3A4 activity and systemic drug levels might improve our understanding of the biology of therapy resistance and enable an actionable path to improve clinical outcomes.
Citation Format: Pragya Kumar, Robert Vander Velde, Malgorzata Weh, Andriy Marusyk. Acceleration of drug metabolism mediated by CYP3A4 enzyme activation provides a bona fide environmental resistance mechanism to targeted therapies [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr A027.