A Study of Mipasetamab Uzoptirine (ADCT-601) in Participants With Solid Tumors

Inclusion Criteria:

1. Male or female participant aged 18 years or older.

2. Pathologic diagnosis of solid tumor malignancy that is locally advanced ormetastatic at time of screening: Part 1:

3. Combination therapy arms: Selected sarcoma indications from the following 2separate categories.

• Soft tissue sarcoma: leiomyosarcoma, liposarcoma, undifferentiatedpleomorphic sarcoma (UPS; covering malignant fibrous histiocytoma) andsynovial sarcoma.
• Bone sarcoma: Ewing's sarcoma (including extraskeletal), osteosarcoma, andchondrosarcoma.

2. Monotherapy arms:

• Sarcoma indications (including those listed for combination therapy arms)regardless of AXL gene amplification status.
• NSCLC regardless of AXL gene amplification status.
• Solid tumors (lymphomas participants are excluded) with known AXL geneamplification. Part 2:

1. Combination therapy arms: Sarcoma indications and PAAD.

2. Monotherapy arms: PAAD, NSCLC and solid tumors with AXL expression.

3. Participants who are refractory to or intolerant to available standard therapy(ies)known to provide clinical benefit for their condition per Investigator judgment.

4. Participants with measurable disease as determined by Response Evaluation Criteriain Solid Tumors (RECIST) v1.1.

5. Eastern Cooperative Oncology Group (ECOG) performance status 0 - 1.

6. PAAD only: Royal Marsden Hospital Prognostic Score 0 - 1.

Exclusion Criteria:

1. History of recent infection requiring intravenous (IV) antibiotics, IV antiviral, orIV antifungal treatment within 4 weeks of Cycle 1 Day 1 (C1D1).

2. Symptomatic central nervous system (CNS) metastases or evidence of leptomeningealdisease (brain magnetic resonance imaging [MRI] or previously documentedcerebrospinal fluid [CSF] cytology). Previously treated asymptomatic CNS metastasesare permitted provided that the last treatment (systemic anticancer therapy and/orlocal radiotherapy) was completed ≥4 weeks prior to Day 1 except usage of low doseof steroids on a taper (i.e., up to 10 mg prednisone or equivalent on Day 1 andconsecutive days is permissible if being tapered down). Participants with discretedural metastases are eligible.

3. Clinically significant third space fluid accumulation (i.e., ascites requiringdrainage or any serosal effusion that is either requiring drainage or associatedwith shortness of breath).

4. Active diarrhea Common Terminology Criteria for Adverse Events (CTCAE) Grade 2 or amedical condition associated with chronic diarrhea (such as irritable bowelsyndrome, inflammatory bowel disease).

5. Use of any other experimental medication within 14 days prior to start of study drug (C1D1).