Background: INT230-6 is a novel intratumoral (IT) agent with a dual anti-cancer mechanism (tumor cytoreduction while stimulating antigen presentation and recruitment of T-cells). The drug is comprised of cisplatin (CIS) and vinblastine (VIN) co-formulated with an amphiphilic molecule that enables drug dispersion throughout tumors and passive diffusion into cancer cells following IT delivery. In the neoadjuvant setting, a single injection can cause necrosis in > 95% of the tumor and recruit TILs. Combining with anti-CTLA-4 improved responses in preclinical models. Methods: INT230-6 dose is set by the tumor’s longest diameter and is proportional to the injected disease volume. INT230-6 is administered IT Q2W for 5 treatment sessions followed by maintenance every 9 weeks as monotherapy or with IPI 3mg/kg IV Q3W for 4 doses. Biopsies from injected tumors are obtained pretreatment and Day 28 for immunoprofiling. Results: 22 subjects with various advanced STS histologies with a median age of 64 and a median of 3 prior systemic therapies were enrolled (11 INT230-6 alone, 11 IPI combination). There were 178 image-guided IT INT230-6 injections (107 to deep tumors) at INT230-6 doses ranging from 5 to 242 mL (121mg CIS, 24.2mg VIN, doses which vastly exceed the usual IV doses of these drugs). PK analysis showed that > 95% of drug agents remain in the tumor. The most common (> 25%) all-grade related adverse events (AEs) in evaluable monotherapy subjects (n = 10) were pain (80%), decreased appetite (40%), nausea (40%), anemia (30%), fatigue (30%) and vomiting (30%). Tolerability was similar for the combination with IPI. Most events were low grade. The incidence of grade 3 AEs for the INT230-6 arm was 30% and for the IPI combination was 10%. There were no related grade 4 or 5 AEs in either cohort. RECIST metrics may not accurately reflect clinical benefit with this treatment given large volumes of INT230-6 is repeatedly injected into a tumor and local inflammation may occur. Paired biopsies showed reduction in proliferating tumor cells and an increase in T-cell infiltrates. The disease control rate at the first imaging timepoint for evaluable INT230-6 subjects (n = 9) was 56% and for evaluable IPI combination (n = 5) was 80%. Abscopal effects were seen in 2 monotherapy subjects, though most uninjected tumors were not tracked. The estimated 1-year overall survival was 88% for the IPI combo and 60% for the monotherapy cohort. Conclusions: IT INT230-6 is well tolerated as monotherapy and combined with IPI. STS, which is typically not sensitive to immunotherapy, may be amenable to INT230-6 or IPI combo to create antigens and promote a systemic immune response. Preliminary efficacy using INT230-6 alone is encouraging and will be evaluated in a global phase 3 trial. Further evaluation is needed to determine whether the addition of IPI may improve patient outcomes. Clinical trial information: NCT03058289.