Testing the Anti-Cancer Drug, Brenetafusp (IMCF106C), in Rare Cancers

Inclusion Criteria: * Patients must have metastatic or unresectable synovial sarcoma or myxoid/round cell liposarcoma confirmed by molecular testing (fluorescence in situ hybridization \[FISH\], immunohistochemistry \[IHC\] for fusion protein, or next-generation sequencing \[NGS\]) * Patients must be HLA-A\*02:01 positive. If HLA-A\*02:01 status is already known (from standard of care testing in a Clinical Laboratory Improvement Act \[CLIA\]-certified laboratory, e.g., in synovial sarcoma), then results from the patient record should be submitted. For patients with unknown HLA-A\*02:01 status, pre-enrollment blood should be submitted for testing through the American National Red Cross Histocompatibility Laboratory Services - Philadelphia for testing * Patients must have measurable disease, defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded for non-nodal lesions and short axis for nodal lesions) as ≥ 20 mm (≥ 2 cm) by chest x-ray or as ≥ 10 mm (≥ 1 cm) with CT scan, MRI, or calipers by clinical exam * Patients must have received at least one line of systemic therapy (neo/adjuvant chemotherapy counts as a line of therapy). The number of prior lines for metastatic or unresectable disease is limited to three (3) * Age ≥ 18 years. Because no dosing or adverse event data are currently available on the use of brenetafusp (IMC-F106C) in patients \< 18 years of age, children are excluded from this study * Eastern …