A Study of VRN110755 in Patients With EGFR-Mutant Non-Small Cell Lung Cancer

Inclusion Criteria: * Adults aged 18 years or older (19 years or older in the Republic of Korea). * Able to understand, sign, and provide written informed consent. * Histologically or cytologically confirmed advanced, metastatic, or recurrent predominantly nonsquamous non-small cell lung cancer (NSCLC) with a documented epidermal growth factor receptor (EGFR) mutation. * At least one measurable extracranial lesion according to Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1. * Documented EGFR mutation determined by tumor tissue or liquid biopsy. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Able to swallow oral capsules and comply with study procedures. * Women of childbearing potential must have a negative pregnancy test, must not be breastfeeding, and must agree to use effective contraception during the study and for 7 months after the last safety follow-up visit. Men must agree to use effective contraception during the study and for 6 months after the last safety follow-up visit. * No appropriate standard treatment options are available or standard treatment is not considered feasible, in the opinion of the investigator. * Participants must meet the disease-specific eligibility criteria for one of the following study groups: * Phase 1a * NSCLC with EGFR activating, resistant, uncommon, or complex mutations, including but not limited to exon 19 deletion (Del19), L858R, C797S, or other uncommon EGFR mutations. * Radiographic disease progression following at least 2 cycles of prior EGFR tyrosine kinase inhibitor (TKI) therapy or discontinuation of prior EGFR TKI therapy because of toxicity, with no remaining standard therapy expected to provide clinical benefit. * Phase 1b - Cohort A * NSCLC with EGFR exon 19 deletion or L858R mutation plus a C797X resistance mutation following disease progression after first-line treatment with a third-generation EGFR TKI (including osimertinib, lazertinib, or aumolertinib). * Phase 1b - Cohort B * Treatment-naïve NSCLC with common EGFR mutations. * Phase 1b - Cohort C * NSCLC with atypical or uncommon EGFR mutations (including G719X, L861Q, S768I, E709X, R776H, L747S, or combinations of these mutations) previously treated with at least one systemic therapy, including an EGFR TKI, with no remaining standard therapy expected to provide clinical benefit. * Phase 1b - Cohort D * Treatment-naïve NSCLC with atypical EGFR mutations. Exclusion Criteria: * Received an investigational anticancer therapy within 14 days or 5 half-lives (whichever is longer) before the first dose of study treatment. * Unresolved side effects from previous anticancer therapy greater than Grade 1 according to the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), except for Grade 2 peripheral neuropathy or alopecia. * Pregnant or breastfeeding, or planning to become pregnant during the study. * NSCLC with an EGFR or HER2 exon 20 insertion mutation. * Another active malignancy within the past 3 years, with the exception of adequately treated cancers considered cured. * Inadequate bone marrow, kidney, or liver function based on protocol-defined laboratory criteria. * Active infection requiring systemic antibacterial, antifungal, or antiviral therapy within 14 days before the first dose of study treatment. * Active hepatitis B or hepatitis C infection, or known human immunodeficiency virus (HIV) infection. * Receipt of a live vaccine within 4 weeks before the first dose of study treatment. * Use of strong or moderate cytochrome P450 (CYP) 3A inhibitors or inducers, certain herbal supplements, or other prohibited medications within the protocol-defined washout period. * Major surgery within 4 weeks before the first dose of study treatment or incomplete recovery from major surgery. * Receipt of prior anticancer therapy within the protocol-defined washout period, including systemic therapy, immunotherapy, or radiotherapy. * Symptomatic or uncontrolled central nervous system (CNS) metastases or spinal cord compression requiring increasing doses of corticosteroids. Participants with treated and stable CNS metastases or asymptomatic CNS disease may be eligible. * Requirement for systemic corticosteroid therapy exceeding the protocol-defined limit. * Clinically significant cardiovascular disease, including prolonged QT interval, clinically significant arrhythmias, recent myocardial infarction, unstable angina, congestive heart failure, uncontrolled hypertension, reduced left ventricular ejection fraction, or use of medications known to prolong the QT interval. * History of interstitial lung disease, noninfectious pneumonitis requiring steroid treatment, or current interstitial lung disease or pneumonitis. * Inability to swallow oral capsules or gastrointestinal disorders that may interfere with absorption of study treatment. * Known allergy or hypersensitivity to VRN110755 or any of its components. * Alcohol or drug abuse within the previous 2 years or any medical, psychological, or social condition that, in the opinion of the investigator, would interfere with study participation or interpretation of study results. * Use of proton pump inhibitors, histamine-2 receptor antagonists, or locally acting antacids within the protocol-defined washout period or inability to comply with protocol requirements for acid-reducing medications. * For Phase 1b and Phase 2 only: Presence of another targetable oncogenic driver alteration with an approved targeted therapy, including MET or HER2 amplification; ALK, ROS1, NTRK, or RET fusion; or BRAF V600E or KRAS G12X mutation.