A Phase 1/1b Study of IAM1363 in HER2 Cancers

Key Inclusion Criteria: * Age ≥ 18 years * Have relapsed/refractory HER2-altered malignancy; for selected cohorts, prospective confirmation of HER2 alteration by central testing is required * Have progression of disease after the last systemic therapy, or be intolerant of last systemic therapy * Have radiographically measurable disease by RECIST v1.1 and/or RANO-BM * Eastern Cooperative Oncology Group (ECOG) performance score 0-1 * Have adequate baseline hematologic, liver and renal function * Have left ventricular ejection fraction (LVEF) ≥ 50% * Able to swallow oral medication Key Exclusion Criteria: * Clinically significant cardiac disease * Infection with human immunodeficiency virus (HIV)-1 or HIV-2. Exception: Participants with well-controlled HIV (e.g., CD4 \>350/mm3 and undetectable viral load) are eligible * Current active liver disease including hepatitis A, hepatitis B , or hepatitis C * Refractory nausea and vomiting, malabsorption, external biliary shunt, or significant small bowel resection that would preclude adequate absorption * Uncontrolled diabetes * History of solid organ transplantation * History of Grade ≥2 CNS hemorrhage, or any CNS hemorrhage within 28 days before C1D1 * Prior history of non-infectious interstitial lung disease (ILD). (Exceptions: participants with prior grade 1 ILD that has completely resolved are eligible) * Participants requiring immediate local therapy for brain metastases