The purpose of this study is to determine if the radiotracer, [68Ga]Ga-ABY-025, used for PET imaging can help us better identify and visualize lesions or tumors, in patients who are receiving standard of care therapy HER2+ cancers.

This study will assess a dose of ABY-025 followed by a tracer dose of [68Ga]Ga-ABY-025 in subjects with HER2+ solid cancers, or HER2+ or low breast cancer undergoing or planning to undergo treatment with standard-of-care HER2-targeted therapy for an FDA-approved indication. The study drug will be administered and [68Ga]Ga-ABY-025 PET/CT scan will be obtained the same day after injection of study drug. Patients will have a follow visit 2-7 days post injection of the study drug. Additionally, subjects will undergo standard of care evaluation of their advanced disease per the discretion of their treating physician.

Inclusion Criteria:

1. Age ≥ 18 years.
2. Patients with unresectable locally advanced or metastatic cancer who are eligible for standard of care treatment with HER2-targeted therapy per the discretion of their treating physician for an FDA-approved indication. Patients who are planning to start HER2-targeted therapy at the time of study enrollment. Patients who have recently begun HER2 treatment and have received no more than 6 cycles will be eligible for enrollment.
3. Must have a previous biopsy demonstrating HER2 expression in at least one lesion (HER2+ solid cancer, or breast cancer patients who are HER2+ or HER2-low) as defined by IHC and FISH studies or with HER2 amplification as defined by a liquid biopsy that was done as standard of care testing for the patient's cancer type.
4. Measurable disease on CT, FDG-PET, or MRI imaging for RECIST evaluation; patient must have measurable disease outside the liver.
5. Life expectancy of at least 6 months. Patients with brain metastases are permitted to enroll in this study.

Exclusion Criteria:

1. Measurable sites of disease only in the liver.
2. Inability to comply with study procedures.
3. Hypersensitivity or allergy to any component of [68Ga]Ga-ABY-025.
4. Pregnant or breastfeeding.
5. HER2-negative cancers that have no FDA approved indication for treatment with HER2-directed therapy.
6. Inability to lie flat for 30 minutes during an imaging session.
7. Medical or psychiatric co-morbidities that, in the opinion of the treating physician, would prevent the patient from successfully participating in the study.

It is unknown if and/or how we will plan IPD with outside researchers.