This first-in-human (FIH) study, multi-center, open-label, dose escalation and dose expansion Phase I study to evaluate the safety, tolerability, pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and preliminary anti-tumor activity of D3L-001 in subjects with HER2-positive advanced solid tumors.

Inclusion Criteria:

• Subject must have documented HER2 positivity (determined by immunohistochemistry [IHC], in situ hybridization [ISH], Next Generation Sequencing [NGS] or other analysis techniques as appropriate).
• Subject must have Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Subject must have left ventricular ejection fraction (LVEF) ≥50% by either echocardiography (ECHO) or multiple-gated acquisition (MUGA) within the screening period.
• Subject must have adequate organ and marrow function within the screening period.

Exclusion Criteria:

• Subject has any prior treatment with anti-CD47 or SIRPα agent.
• Subject has any prior treatment without adequate washout periods as defined in the protocol.
• Subject has immunosuppressive medication that is not completed 14 days before the first dose of study medication.
• Subject has uncontrolled intercurrent illness that would limit compliance with study requirements, substantially increase risk of incurring AEs, or compromise the ability of the subject to give written informed consent.
• Subject has unresolved treatment-related toxicities from previous anticancer therapy of NCI CTCAE Grade ≥2 (with exception of vitiligo or alopecia).
• Judgment by the Investigator that the subject should not participate in the study if the subject is unlikely to comply with study procedures, restrictions, and requirements.