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Overcoming acquired resistance to third-generation EGFR inhibitors by targeting activation of intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation, or both


Treatment of EGFR-mutant non-small cell lung cancer (NSCLC) with mutation-selective third-generation EGFR-tyrosine kinase inhibitors (EGFR-TKIs) such as osimertinib has achieved remarkable success in the clinic. However, the immediate challenge is the emergence of acquired resistance, limiting the long-term remission of patients. This study suggests a novel strategy to overcome acquired resistance to osimertinib and other third-generation EGFR-TKIs through directly targeting the intrinsic apoptotic pathway. We found that osimertinib, when combined with Mcl-1 inhibition or Bax activation, synergistically decreased the survival of different osimertinib-resistant cell lines, enhanced the induction of intrinsic apoptosis, and inhibited the growth of osimertinib-resistant tumor in vivo. Interestingly, the triple-combination of osimertinib with Mcl-1 inhibition and Bax activation exhibited the most potent activity in decreasing the survival and inducing apoptosis of osimertinib-resistant cells and in suppressing the growth of osimertinib-resistant tumors. These effects were associated with increased activation of the intrinsic apoptotic pathway evidenced by augmented mitochondrial cytochrome C and Smac release. Hence, this study convincingly demonstrates a novel strategy for overcoming acquired resistance to osimertinib and other 3rd generation EGFR-TKIs by targeting activation of the intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation or both, warranting further clinical validation of this strategy.

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Fig. 1: The combination of osimertinib with an Mcl-1 inhibitor synergistically decreases the survival of osimertinib-resistant cell lines, which are resistant to Mcl-1 modulation by osimertinib.
Fig. 2: The combination of osimertinib with an Mcl-1 inhibitor augments the induction of apoptosis with enhanced mitochondrial release of Cyt C and Smac.
Fig. 3: The combination of osimertinib with a Bax activator synergistically decreases the survival of osimertinib-resistant cell lines.
Fig. 4: The combination of osimetrtinib with a Bax activator enhances induction of apoptosis, mitochondrial release of Cyt C and Smac and Bax oligomerization.
Fig. 5: The three-drug combination of osimertinib, CYD-2-11 and an Mcl-1 inhibitor is lethal to osimertinib-resistant EGFRm NSCLC cell lines, but not to NSCLC cell lines with wild-type EGFR.
Fig. 6: The three-drug combination of osimertinib, CYD-2-11 and an Mcl-1 inhibitor is more effective than either two-drug combination in inducing apoptosis including mitochondrial release of Cyt C and Smac in osimertinib-resistant NSCLC cells.
Fig. 7: The combination of osimertinib with an Mcl-1 inhibitor, a Bax activator, or particularly with both, exerts enhanced effects against the growth of osimertinib-resistant xenografts in nude mice and on induction of apoptosis without enhancing toxicity.


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We thank Dr. A. Hammond in our department for editing the manuscript. This work was supported by Emory University Winship Cancer Institute lung cancer pilot fund (to SYS), NIH/NCI SPORE P50 CA217691 (to XD) and a research fund from Ascentage Pharma (to SYS). TKO, SSR and SYS are Georgia Research Alliance Distinguished Cancer Scientists.

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Authors and Affiliations



Conceptualization: GM, XD, TKO, SSR, DDF, YZ, and S-YS. Investigation: GM, YD, LQ, KAV, and GZ. Methodology: GM, YD, LQ, KAV, GZ and S-YS. Writing/Original Draft: GM, and S-YS. Review/Editing: YD, LQ, KAV, GZ, XD, TKO, SSR, DDF, and YZ. Funding Acquisition: SSR, XD, DDF, YZ and S-YS. Supervision: XD, YZ, and S-YS.

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Correspondence to Shi-Yong Sun.

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Competing interests

TKO is on consulting/advisory board for Novartis, Celgene, Lilly, Sandoz, Abbvie, Eisai, Takeda, Bristol-Myers Squibb, MedImmune, Amgen, AstraZeneca and Boehringer Ingelheim. SSR is on consulting/advisory board for AstraZeneca, BMS, Merck, Roche, Tesaro and Amgen. YZ and DDF are full-time employees and equity shareholders of Ascentage Pharma. SYS received a research fund from Ascentage Pharma. Other authors disclose that they have no potential conflicts of interest.

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Ma, G., Deng, Y., Qian, L. et al. Overcoming acquired resistance to third-generation EGFR inhibitors by targeting activation of intrinsic apoptotic pathway through Mcl-1 inhibition, Bax activation, or both. Oncogene 41, 1691–1700 (2022).

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