A First-in-human, Phase 1/2, Multicenter, Open-label, Dose Escalation and Expansion Study to Evaluate the Safety, Pharmacokinetics, and Antitumor Activity of ADCE-D01, a Humanized Anti-human uPARAP Antibody Linked to a Topoisomerase I Inhibitor, in Patients With Metastatic and/or Unresectable Soft Tissue Sarcoma

Inclusion Criteria: 1. ≥ 18 years of age 2. Histologically confirmed STS with metastatic and/or unresectable disease (not amenable to treatment with curative intent). 3. Prior treatment with at least one but no more than two lines of cytotoxic systemic therapy for metastatic/unresectable disease. 4. Measurable disease as per RECIST v 1.1. 5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 6. Life expectancy of at least 3 months. 7. A male patient must agree to use barrier contraception during the treatment period and for at least 4 months after the last infusion of study treatment, and refrain from donating sperm during this period. Male patients with a pregnant partner must practice sexual abstinence or use a barrier method of contraception (e.g., condom) to prevent exposure of the fetus or neonate. 8. A female patient is eligible if not pregnant, not breast feeding, and not a woman of childbearing potential (WOCBP), or agrees to follow the contraceptive guidance during the treatment period and for at least 7 months after last infusion of study treatment. Exclusion Criteria: 1. Patients who have had systemic anticancer therapy, including any investigational agent within 4 weeks or 5 half-lives (whichever is shorter) prior to study treatment administration. 2. Primary brain malignancy or known, untreated central nervous system (CNS) or leptomeningeal metastases, or symptoms suggesting CNS involvement. 3. Clinically significant cardiovascular disease 4. Patients with acute infection with human immunodeficiency virus (HIV) 1 or HIV 2. 5. Current active liver disease due to hepatitis B 6. History of idiopathic pulmonary fibrosis, organizing pneumonia, drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis on a chest computed tomography (CT) scan at screening.