Clinical Activity of Single Dose Systemic Oncolytic VSV Virotherapy in Patients with Relapsed Refractory T-Cell Lymphoma

Clinical success with intravenous (IV) oncolytic virotherapy (OV) has to date been anecdotal. Here, we conducted a phase 1 clinical trial of systemic OV therapy and investigated the mechanisms of action in responding T-cell lymphoma (TCL) patients. A single IV dose of VSV-IFNβ-NIS was administered to patients with relapsed refractory hematologic malignancies to determine safety and efficacy across 4 dose levels (DL). Correlative studies were undertaken to evaluate viremia, virus shedding, virus replication and immune responses. Fifteen patients received VSV-IFNβ-NIS (7 multiple myeloma, 7 TCL, 1 acute myeloid leukemia); 3 patients were treated at each DL1 through DL3 (0.05, 0.17, and 0.5 x 1011 TCID50), and 6 at DL4 (1.7 x 1011 TCID50). There were no dose limiting toxicities. 3 of 7 patients with TCL had RECIST responses: a 3-month PR at DL2, a 6-month PR and a durable CR ongoing at 20 months at DL4. Viremia peaked at the end of infusion and no infectious virus shedding was detected. Plasma interferon-β levels, a biomarker of VSV-IFNβ-NIS replication, peaked between 4h and 48h post infusion. The patient with CR had robust viral replication with increased ell free DNA in her plasma, a very high peak IFNβ level of 18,213 pg/ml, a strong anti-VSV neutralizing antibody response, and increased numbers of tumor reactive T-cells. VSV-IFNβ-NIS as a single agent was effective in patients with TCL resulting in durable disease remissions in heavily pretreated patients. Correlative analyses suggest that responses may be due to a combination of direct oncolytic tumor destruction and immune-mediated tumor control. Further clinical testing is warranted. (This trial is registered at www.clinicaltrials.gov as NCT03017820).