Study of ADCT-502 in Patients With Advanced Solid Tumors Withhuman Epidermal Growth Factor Receptor-2 (HER2) Expression

Main Inclusion Criteria:

   - Male or female age 18 years or older

   - Refractory to or intolerant of existing therapy(ies) known to provide clinical benefit
   for their condition.

   - Eastern Cooperative Oncology Group (ECOG) performance status: Part 1: 0-2, Part 2: 0-1

   - Availability of formalin-fixed paraffin-embedded (FFPE) tumor tissue block or
   unstained slides to demonstrate HER2 expression.

   - Pathologic diagnosis of solid tumor malignancy that is locally advanced or metastatic
   at time of Screening with documented HER2 expression.

   - Part 2/Dose Expansion Only: Measurable disease as defined by Response Evaluation
   Criteria in Solid Tumors (RECIST) version 1.1

   - Absolute neutrophil count (ANC) ≥ 1500/mm3 (≥1.5× 109/L).

   - Platelet count ≥100,000 //mm3 (≥100 × 109/L).

   - Hemoglobin ≥ 9 g/L (≥5.6 mmol/L).

   - Aspartate transaminase (AST) and alanine aminotransferase (ALT) ≤ 2.5 x upper limit of
   normal (ULN); or ≤ 5.0 × ULN if liver metastases are present.

   - Total bilirubin ≤ 1.5× ULN (or ≤ 3× ULN, with direct bilirubin ≤1.5 × ULN, in
   participants with known Gilbert syndrome).

   - Creatinine ≤ 1.5× ULN; or, if serum creatinine > 1.5 × ULN, a measured creatinine
   clearance must be >60mL/min/1.73m2 as calculated by the Cockcroft and Gault equation
   for participants to be eligible.

   - Women of childbearing potential must agree to use a highly effective method of
   contraception from the time of giving informed consent until at least 16 weeks after
   the last dose of ADCT-502. Men with female partners who are of childbearing potential
   must agree that they or their partners will use a highly effective method of
   contraception from the time of giving informed consent until at least 16 weeks after
   the participant receives his last dose of ADCT-502.

Main Exclusion Criteria:

   - Known history of ≥ Grade 3 hypersensitivity to a therapeutic antibody.

   - Known history of positive serum human anti-drug antibody (ADA) to trastuzumab.

   - Major surgical procedure or significant traumatic injury, radiotherapy, chemotherapy,
   targeted therapy, hormone therapy, or other anticancer therapy.

   - Failure to recover to Grade 0 or Grade 1 from acute non-hematologic toxicity due to
   previous therapy, prior to screening (with the exception of alopecia).

   - Central Nervous System (CNS) disease only.

   - Symptomatic CNS metastases or evidence of leptomeningeal disease.

   - Active cardiovascular disease or significant history thereof.

   - Other active disease including but not limited to ulceration of the upper
   gastrointestinal tract, autoimmune disease, HIV infection, active Hepatitis B virus
   (HBV) and hepatitis C virus (HCV) infection.

   - Breastfeeding or pregnant.

   - Other concurrent severe and/or uncontrolled medical conditions.