ELVN-002 With Trastuzumab +/- Chemotherapy in HER2+ Solid Tumors, Colorectal and Breast Cancer

Inclusion Criteria: * Pathologically or histologically documented solid tumor. * Locally advanced or relapsed/refractory disease or unresectable metastatic disease. * HER2-positive disease based on the following local testing: * Colorectal cancer: IHC3+, IHC2+/ISH+, NGS amplification by tissue (no RAS or BRAF mutation allowed) * Breast cancer: IHC3+ or IHC2+/ISH+ by tissue * Gastric cancer: IHC3+ or IHC2+/ISH+ by tissue * Other cancers: IHC3+, IHC2+/ISH+, NGS amplification by tissue or ctDNA * Prior therapies for Part 1 (Dose Escalation ELVN-002 + trastuzumab): * Colorectal cancer: treated with prior fluoropyrimidine, oxaliplatin, irinotecan-based regimens, anti-epidermal growth factor receptor (EGFR) treatment (if clinically indicated), anti-vascular endothelial growth factor (VEGF) treatment (if clinically indicated), and an anti-programmed death ligand 1 (PD-(L)-1) treatment (if the tumor is microsatellite instability (MSI)-high/deficient mismatch repair (dMMR) * Breast cancer: treated with prior taxane, pertuzumab, trastuzumab, and fam-trastuzumab deruxtecan (T-DXd) if available and appropriate based on local standard of care and investigator's assessment * Gastric cancer: treated with trastuzumab/platinum fluorouracil containing regimen and T-DXd. * Other cancers: progressed during or after ≥ 1 prior line of systemic therapy for locally advanced unresectable or metastatic disease * Prior HER2 targeted therapy is allowed * Prior therapies for Part 2 (…