Adult Soft Tissue Sarcoma Clinical Trials

• Histopathologic documented diagnosis of R/R osteosarcoma

• Must have disease characterized by at least one of the following (Participants meeting only (b.), only (c.), or only (b. and c.) must be discussed with and receive written approval from the Sponsor to qualify).

∙ Measurable as defined in RECIST 1.1

‣ Evaluable non-measurable disease as per RECIST 1.1

‣ Bone only without a soft tissue component: must be 18F-FDG-PET avid and evaluable by serial 18F-FDG-PET imaging studies.

• Age: a. First Cohort in Phase 1: ≥ 18 years-of-age at the time of signature of the main study ICF. b. Second and subsequent cohorts, in Phase 1 and all participants in Phase 2: ≥12years-of-age at the time of signature of the main ICF.

• Performance Status:

∙ Eastern Cooperative Oncology Group (ECOG) Performance Score (PS): 0 - 2

‣ Lansky PS ≥ 50.

• Body weight: ≥ 30 kg.

• Tumor biopsies; Fresh or Archival

• Progression following at least one course of chemotherapy, which includes neoadjuvant / perioperative systemic therapy.

• All adverse events (AEs) related to prior therapies (chemotherapy / systemic therapies, radiation, surgery) must have resolved to Grade 1 or baseline

• Organ Function

⁃ Pregnancy Women of Child-Bearing Potential (WOCBP) must have a negative serum pregnancy test result at screening

⁃ Contraception- Male participants with a WOCBP partner must use 2 forms of acceptable contraception

⁃ Written informed consent and/or assent must be obtained according to local guidelines and signed and dated by the participant, parent, and/or legal guardian prior to the performance of any study-specific procedures, sampling, or analyses