The purpose of this study is to facilitate access to trabectedin for eligible previously treated patients with soft tissue sarcoma (STS), who cannot be expected to benefit from currently available therapeutic options but who may benefit from treatment with trabectedin. The safety profile of trabectedin will be evaluated to further assess the potential risks of trabectedin treatment.

This is a multicenter, open-label (all people know the identity of the intervention), single-arm study. It will consist of 2 Phases: a Screening Phase (up to 21 days before the first dose administration), and Treatment Phase (for patients meeting the continuation criteria). During the Treatment Phase, patients will receive a dose of 1.5 mg/m2 trabectedin intravenous formulation administered as a 24-hour infusion on Day 1 of each suggested 21-day treatment cycle. All patients will receive 20 mg dexamethasone (or corticosteroid equivalent to dexamethasone). Number of cycles is not specified for this study. Patients may continue to receive treatment as long as they obtain an overall clinical benefit, ie, until there is clear evidence of disease progression or unacceptable toxicity, as judged by the investigator. Trabectedin is the first of a new class of antitumor agents. Previous studies with trabectedin in patients who had been previously treated for soft tissue sarcoma have suggested that treatment with trabectedin resulted in tumor shrinkage, disease stabilization, and improved survival rates. However, hematologic toxicity, hepatic toxicity, and renal impairment were also observed in these patients. The safety profile of trabectedin will be evaluated to further assess the potential risks of trabectedin treatment in patients previously treated for soft tissue sarcoma who are not expected to benefit from currently available therapeutic options for treatment of soft tissue sarcoma. Safety will be monitored throughout the study.

Inclusion Criteria:

• Unresectable advanced or metastatic histologically proven soft tissue sarcoma (STS). Eligibility will include adult participants with desmoplastic small round cell tumor
• Must have relapsed or had progressive disease following standard of care treatment with chemotherapy prior to enrollment or intolerant to prior standard of care treatment with chemotherapy due to safety issues
• Recovery from toxic effects of prior therapies to Grade 1 or better according to National Cancer Institute-Common Terminology Criteria of Adverse Events (criteria used to grade the severity of toxic effects on a scale from 0 to 5 - Grade 1 = mild in severity, Grade 0 = no severity)
• Clinical test results within acceptable limits (ie, hematologic, clinical chemistry and hepatic function test results)
• Female participants must be postmenopausal, surgically sterile, abstinent, or if sexually active, be practicing 2 effective methods of birth control (eg, prescription hormonal contraceptive, intrauterine device, double-barrier method [eg, condoms, occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam, cream, gel, film, or suppository]), before entry, and must agree to continue to use these same methods of contraception throughout the study and for 3 months thereafter. Male participants must agree to use an adequate contraception method as deemed appropriate by the investigator (eg, vasectomy, double-barrier, partner using effective contraception) and to not donate sperm for a minimum of 5 months after treatment discontinuation

Exclusion Criteria:

• Diagnosis of Ewing's sarcoma or osteosarcoma, less than 3 weeks from last dose of radiation, systemic cytotoxic therapy (or 4 half lives, whichever is longer)
• Active symptomatic viral hepatitis or chronic liver disease
• Significant uncontrolled cardiac condition, including New York Heart Association Class II or greater heart failure, uncontrolled angina pectoris, myocardial infarction within 6 months before enrollment, significant pericardial disease, or uncontrolled or arrhythmias
• Active infection
• Female participant who is pregnant or breastfeeding