A Study of the c-Kit Specific Antibody-Drug Conjugate NN3201 for Advanced and/or Metastatic Solid Tumors Known to Express c-Kit

Key Inclusion Criteria: Subjects must meet the following criteria to be eligible for enrollment into the study: 1. Histologically or cytologically confirmed locally advanced, metastatic, and/or unresectable GIST, SCLC, ACC, uveal melanoma, NET ChRCC or ccRCC. 2. Subjects must have received the following treatment: Part A (Dose Escalation): i. Treatment with imatinib for GIST (at least one line of therapy with imatinib) or ii. Progressive/refractory, ineligible, or intolerant to available standard therapy (or subject declines standard therapy) for c-Kit-associated solid tumors (ACC, uveal melanoma, NET ChRCC or ccRCC) Part B (Dose Expansion): i. Treatment with imatinib for GIST (at least one line of therapy with imatinib) or ii. Progressive/refractory, ineligible, or intolerant to available standard therapy (or subject declines standard therapy) for Extensive stage SCLC or iii. Progressive/refractory, ineligible, or intolerant to available standard therapy (or subject declines standard therapy) for c-Kit-associated solid tumors (ACC, uveal melanoma, NET or ChRCC or ccRCC). 3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 4. Life expectancy ≥ 3 months before starting NN3201 in the opinion of the Investigator. 5. Age ≥ 18 years. 6. Laboratory values demonstrating adequately functioning kidney, liver and bone marrow (hematology). 7. Adequate heart function as measured by ECHO/MUGA scan. 8. Time between prior anticancer therapy including investigational agents and first dose of NN3201 as below: 1. Cytotoxic chemotherapy - At least 21 days 2. Non-cytotoxic chemotherapy (e.g., small molecule inhibitor) - At least 14 days 3. Nitrosoureas - At least 6 weeks 4. Monoclonal antibody(ies) - At least 28 days 5. Radiotherapy - At least 14 days from local site radiation therapy 9. Negative Serum/urine pregnancy test (for subjects of childbearing potential) 10. All subjects of childbearing potential must agree to use contraception throughout the study and for additional 120 days after the last dose of assigned treatment. Subjects must refrain from donating sperm during the same period or Subjects who do not have childbearing potential are confirmed post-menopausal or sterile. 11. Voluntary agreement to provide written informed consent and have willingness and ability to comply with all aspects of the protocol. Key Exclusion Criteria: 1. Has received prior therapy with a c-Kit agent (except GIST subjects). 2. Known brain metastases that are untreated, symptomatic, or require therapy to control symptoms. 3. A condition requiring systemic treatment with corticosteroids (\>10 mg daily prednisone equivalent) or other immunosuppressive medications within 14 days prior to administration of study drugs (inhaled corticosteroids are allowed). 4. Any prior treatment-related (i.e., chemotherapy, immunotherapy, radiotherapy) clinically significant toxicities that have not resolved to Grade ≤ 1 or prior treatment-related toxicities that are clinically unstable and clinically significant at Study Entry, Day -2 to Cycle 1 Day 1. 5. Major surgery within 30 days before the first dose of study drug treatment in Cycle 1 on Day 1 (port placement for venous access is not considered major surgery). 6. Significant cardiovascular impairment. 7. Significant screening electrocardiogram (ECG) abnormalities. 8. Known active and clinically significant bacterial, fungal, or viral infection. 9. Uncontrolled hypertension defined as systolic blood pressure ≥ 160mmHg and/or diastolic blood pressure ≥ 100mmHg, despite optimal medical management. 10. Venous thrombosis or pulmonary embolism within the last 3 months prior to the screening. 11. Ongoing or active infection requiring intravenous treatment with anti-infective therapy or systemic therapy and/or any identified active COVID-19 infection. 12. Any other major illness that, in the Investigator's judgment, will substantially increase the risk associated with the subject's participation in this study. 13. People who are pregnant or breastfeeding. Other inclusion and exclusion criteria must also be met to be eligible to participate in this study.