First-In-Human Study of STX-721 in Participants With Locally Advanced or Metastatic Non-Small Cell Lung Cancer Harboring EGFR Exon 20 Insertion Mutations

Key Inclusion Criteria: Has histologically- or cytologically confirmed diagnosis of NSCLC Stage IIIB/C or IV not eligible for curative intent surgery or chemoradiation. Tumor tissue EGFR exon 20 insertion mutations confirmed by qualified local laboratories. Has new or recent tumor biopsy (collected at screening, if feasible) or archival tumor specimen collected in the past 10 years available for genomic profiling (see lab manual for minimum tissue requirements). Is ≥18 years of age at the time of signing the ICF. Has Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1. Key Exclusion Criteria: Has a tumor that is known to harbor concurrent T790M and C797S resistance mutations. Has history (within ≤2 years before screening) of solid tumor or hematological malignancy that is histologically distinct from NSCLC. Has symptomatic brain or spinal metastases. Has toxicities from previous anticancer therapies that have not resolved to baseline levels or to CTCAE Grade ≤1, except for alopecia and peripheral neuropathy. Has any condition for which, in the opinion of the investigator, participation would not be in the best interest of the participant (e.g., could compromise the participant's well-being) or would prevent, limit, or confound the protocol-specified assessments.