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Introduction: Despite the availability of several epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), most patients with non-small-cell lung cancer (NSCLC) eventually develop resistance to these agents. Notably, EGFR _C797S mutations confer resistance to the third-generation EGFR-TKI osimertinib and no approved post-osimertinib targeted pharmacology options are currently available. BLU-945 is a novel, reversible, and orally available next-generation EGFR-TKI that selectively targets EGFR-activating ( EGFR m) and resistance mutations (including EGFR_C797S) with nanomolar potency while sparing wild-type EGFR in vitro. Methods: In vitro activity of BLU-945 as a single agent and in combination with osimertinib was tested in engineered EGFR -mutant cell lines as well as patient-derived cells and patient-derived organoids. In vivo activity was evaluated in osimertinib-resistant patient-derived xenograft mouse models. Three patient cases from the global, first-in-human, phase I/II SYMPHONY trial (NCT04862780) demonstrating the clinical efficacy of BLU-945 were reported. Results: In vitro BLU-945 demonstrated inhibited cell viability and growth of EGFR -mutant/osimertinib-resistant cell lines. BLU-945 demonstrated in vivo tumor shrinkage in osimertinib-resistant models of NSCLC (osimertinib second line: EGFR _L858R/C797S and third line: EGFR _ex19del/T790M/C797S and L858R/T790M/C797S) both as monotherapy and in combination with osimertinib. BLU-945 also demonstrated tumor shrinkage in patients from the SYMPHONY trial. Conclusion: Our findings demonstrate the preclinical and early clinical activity of BLU-945 in EGFR m NSCLC progressing on previous EGFR-TKIs.

IntroductionOsimertinib is recommended by major guidelines for use in the adjuvant setting in patients with EGFR mutation-positive NSCLC following the significant improvement in disease-free survival observed in the Phase III ADAURA trials. Due to limited real-world data in the adjuvant setting, little guidance exists on how to approach potential recurrences either during or after the completion of the treatment. This study aimed to reach a broad consensus on key treatment decision criteria in the events of recurrence.MethodsTo reach a broad consensus, a modified Delphi panel study was conducted consisting of two rounds of surveys, followed by two consensus meetings and a final offline review of key statements. An international panel of experts in the field of NSCLC (n=12) was used to provide clinical insights regarding patient management at various stages of NSCLC disease including patient monitoring, diagnostics, and treatment approach for specific recurrence scenarios. This study tested recurrences occurring 1) within or outside the central nervous system (CNS), 2) during or after the adjuvant-osimertinib regimen in NSCLC disease which is 3) amenable or not amenable to local consolidative therapy.ResultsPanellists agreed on various aspects of patient monitoring and diagnostics including the use of standard techniques (e.g., CT, MRI) and tumour biomarker assessment using tissue and liquid biopsies. Consensus was reached on 6 statements describing treatment considerations for the specific NSCLC recurrence scenarios. Panellists agreed on the value of osimertinib as a monotherapy or as part of the overall treatment strategy within the probed recurrence scenarios and acknowledged that more clinical evidence is required before precise recommendations for specific patient populations can be made.DiscussionThis study provides a qualitative expert opinion framework for clinicians to consider within their treatment decision-making when faced with recurrence during or after adjuvant-osimertinib treatment.

Molecularly targeted cancer therapy has improved outcomes for patients with cancer with targetable oncoproteins, such as mutant EGFR in lung cancer. Yet, the long-term survival of these patients remains limited, because treatment responses are typically incomplete. One potential explanation for the lack of complete and durable responses is that oncogene-driven cancers with activating mutations of EGFR often harbor additional co-occurring genetic alterations. This hypothesis remains untested for most genetic alterations that co-occur with mutant EGFR. Here, we report the functional impact of inactivating genetic alterations of the mRNA splicing factor RNA-binding motif 10 (RBM10) that co-occur with mutant EGFR. RBM10 deficiency decreased EGFR inhibitor efficacy in patient-derived EGFR-mutant tumor models. RBM10 modulated mRNA alternative splicing of the mitochondrial apoptotic regulator Bcl-x to regulate tumor cell apoptosis during treatment. Genetic inactivation of RBM10 diminished EGFR inhibitor–mediated apoptosis by decreasing the ratio of (proapoptotic) Bcl-xS to (antiapoptotic) Bcl-xL isoforms of Bcl-x. RBM10 deficiency was a biomarker of poor response to EGFR inhibitor treatment in clinical samples. Coinhibition of Bcl-xL and mutant EGFR overcame the resistance induced by RBM10 deficiency. This study sheds light on the role of co-occurring genetic alterations and on the effect of splicing factor deficiency on the modulation of sensitivity to targeted kinase inhibitor cancer therapy.