Inclusion Criteria:

          -  Male or female, age ≥ 18 years at the time of signing first informed consent;

          -  Patient with a histologically-confirmed, locally advanced or metastatic tumour who has
             progressed on standard therapy or for whom no standard therapy exists, with the
             following restriction:

               -  Part 1: solid tumours of any origin;

               -  Part 2: breast cancer, ovarian cancer or endometrial carcinoma/carcinosarcoma;

          -  HER2 tumor status at least 1+ as assessed by immunohistochemistry (IHC) as determined
             by the local laboratory;

          -  Presence of a tumor lesion accessible for biopsy and patient should be willing to
             undergo a fresh biopsy for central HER2 testing and genetic testing, unless adequate
             (biopsy) tumour material is available obtained < 6 months prior to signing the main
             informed consent;

          -  At least one measurable cancer lesion as defined by the Response Evaluation Criteria
             for Solid Tumours (RECIST version 1.1);

          -  Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1;

          -  Adequate organ function.

        Exclusion Criteria:

          -  Having been treated with:

               1. DUBA-containing ADCs at any time;

               2. Anthracycline treatment within 8 weeks prior to start of study treatment;

               3. Other anticancer therapy including chemotherapy, immunotherapy, or
                  investigational agents within 4 weeks prior to start of study treatment or 5
                  times the half-life of the therapy, whichever is shorter;

               4. Radiotherapy within 4 weeks prior to start of study treatment or within 1 week
                  for palliative care (as long as the lungs were not exposed);

               5. Hormone therapy within 1 week prior to start of study treatment. The patient must
                  have sufficiently recovered from any treatment-related toxicities to NCI CTCAE
                  Grade ≤ 1 (except for toxicities not considered a safety risk for the patient at
                  the investigator's discretion);

          -  History or presence of keratitis;

          -  Left ventricular ejection fraction (LVEF) < 50% as assessed by either echocardiography
             or multigated acquisition (MUGA) scan at screening, or a history of clinically
             significant decrease in LVEF during previous trastuzumab containing treatment leading
             to permanent discontinuation of treatment;

          -  History (within 6 months prior to start of study treatment) or presence of clinically
             significant cardiovascular disease such as unstable angina, congestive heart failure,
             myocardial infarction, uncontrolled hypertension, or cardiac arrhythmia requiring
             medication;

          -  History or presence of idiopathic pulmonary fibrosis, organizing pneumonia (e.g.
             bronchiolitis obliterans), drug-induced pneumonitis, or idiopathic pneumonitis, or
             evidence of active pneumonitis on screening chest CT scan;

          -  Severe, uncontrolled systemic disease (e.g. clinically significant cardiovascular,
             pulmonary, or metabolic disease) at screening;

          -  Symptomatic brain metastases, brain metastasis requiring steroids to manage symptoms
             or treatment for brain metastases within 8 weeks prior to start of study treatment.