Background: Combination trabectidin (T) and nivolumab (N) has been shown to be a safe and effective therapy in soft tissue sarcoma (STS). Intratumoral injection of talimogene laherparepvec (TVEC) has a local oncolytic effect, and increases immune response via enhanced recruitment of antigen presenting cells, and thereby cytotoxic immune response. This study aims to determine if the addition of TVEC to combination trabectedin and nivolumab is effective and safe in advanced sarcoma. Methods: Eligible patients include patients ≥ 18 years of age with locally advanced unresectable or metastatic STS, measurable disease by RECIST v1.1, and at least one accessible tumor for TVEC intratumoral injection. N (3 mg/kg i.v. q 2 weeks), T (1.2 mg/m² i.v. q 3 weeks) and TVEC (1x10e⁸ PFU/ml q 2 weeks depending on tumor size) were administered. A test dose of TVEC (1x10e⁶ PFU/ml) was initially given, followed three weeks later by full dose TVEC. Primary endpoint: Progression-free survival (PFS); Secondary endpoints: (1) Best overall response during treatment period, (2) PFS rate at 6 and 9 months, (3) Overall survival (OS) rate at 6, 9, and 12 months, (4) Incidence of conversion from unresectable to resectable tumor, and (5) Incidence of treatment-related adverse events. Interim. Results: There were 36 evaluable subjects under the Modified Intention-to-Treat (MITT) population, having completed the first cycle of TNT and a CT or MRI scan at the 6-week follow-up period. The most common histological subtypes include leiomyosarcoma (9), liposarcoma (5), spindle cell sarcoma (3), pleomorphic sarcoma (2), Ewing’s sarcoma (2), and other (5). Median number of prior lines of therapy was 4 (range 1-8). Best Overall Response by RECIST v1.1 = 3 PR, 27 SD, 5 PD. One patient, with previously unresectable disease was taken for resection and was found to have 100% necrosis on surgical pathology. Disease control rate (CR+PR+SD) was 86.1%. The median PFS was 5.5 (range: 1-18) months; 6-month PFS rate: 62.1%. Median PFS on therapy immediately preceding this trial was 2.0 months (range = 1-14 months). There were 47 evaluable subjects for OS analysis under the Intention-to-Treat (ITT) population having received at least one dose of T and N. The median OS was 9.0 (range 0-20) months; 6-month OS rate: 73%. Safety analysis: There were 47 evaluable subjects under the ITT population. 28% of these patients experienced ³1 SAE. The most common grade 3/4 TRAEs include anemia (12), increased ALT (8), fatigue (4), thrombocytopenia (4), neutropenia (4). There were no grade 3/4 TVEC injection site reactions. 22% of patients in the MITT cohort remain on study. Conclusions: These results suggest that combination therapy with TNT appears to be as effective as standard therapy, with no new safety signals seen. Furthermore, median PFS exceeded that of the immediately preceding lines of therapy in this heavily pre-treated cohort. As data matures, further data will be reported. Clinical trial information: NCT03886311