• Voluntary signed and dated written informed consent of the participants obtained before any study-specific procedure.

• Age ≥ 18 years.

• Histologically confirmed diagnosis of metastatic LMS, in participants not candidates for curative resection.

• Radiologically measurable disease according to the Response Evaluation Criteria in Solid Tumors (RECIST) v.1.1.

• No previous systemic therapy for metastatic disease (i.e., first-line setting) and no previous anthracyclines. Note: prior chemotherapy (without anthracycline) in the context of adjuvant or neoadjuvant therapy is allowed. Prior line/s of hormone therapy in the adjuvant/metastatic setting are also allowed.

• Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤ 1.

• Adequate hematological, renal, metabolic and hepatic function:

‣ Hemoglobin ≥ 9.0 g/dL (participants may have received prior red blood cell \[Red Blood Cell\] transfusion); absolute neutrophil count (ANC) ≥ 2.0 x 10\^9/L, and platelet count

‣ ≥ 100 x 10\^9/L.

⁃ Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3.0 x upper limit of normal (ULN).

⁃ Total bilirubin ≤ 1.5 x ULN or direct bilirubin ≤ ULN if total bilirubin is \> ULN.

⁃ Albumin ≥ 3.0 g/dL.

⁃ Calculated creatinine clearance (CrCL) ≥ 30 mL/min (using Cockcroft and Gault's formula).

⁃ Left ventricular ejection fraction (LVEF) \> 50% assessed by multiple-gated acquisition scan (MUGA) or echocardiography (ECHO) or cardiac magnetic resonance imaging (MRI).

• Wash-out periods:

‣ At least three weeks since last prior systemic treatment.

⁃ At least three weeks since last prior major surgery and one week since last prior minor surgery (port placement is excluded from this wash-out period).

⁃ At least two weeks since last prior radiotherapy.

• Evidence of non-childbearing status for women of childbearing potential (WOCBP). WOCBP must agree to use a highly effective contraceptive measure up to seven months after treatment discontinuation. Fertile male participants with WOCBP partners should use condoms during treatment and for four months following the last investigational medicinal product (IMP) dose.