PDCT-18 (LTBK-03). PHASE I CLINICAL TRIAL WITH ONCOLYTIC VIRUS DNX-2401 FOR DIPGS

Abstract

Delta-24-RGD (DNX-2401 in the clinic) has been tested for adult glioblastoma presenting a safe profile and promising efficacy. Our group has showed that the virus is safe and effective in preclinical models of pHGG and DIPG. Moreover, we showed that the virus is able to trigger an antitumor immune response. These results allowed us to propel a phase I clinical trial for newly diagnosed DIPGs (NCT03178032) where the patients received an intratumoral injection of DNX-2401 (N=12). Tumor biopsy is performed through the cerebellar peduncle, followed by virus injection using a cannula that prevents the reflux. The trial is uncontrolled, unicentric with a 3 + 3 design. The objective of this trial is to determine the safety, tolerability, and toxicity of DNX-2401 in subjects with DIPG. Secondary endpoints are overall survival at 12 months (OS12), percentage of responses and induced immune response against tumor. To date 9 patients have been treated within the trial. Three patients were treated with the D1=1x1010vp and because the lack of toxicity we escalated to the D2= 5x1010vp. The procedure was well tolerated and safe. Patients were home 3–4 days after the injection. All the patients displayed a reduced tumor volume after combined treatment. We performed molecular studies in 8 out of the 9 patients (RNAseq and a thermofisher pediatric panel). Subsequently we evaluated the immune cell composition in the tumor using multiplexed quantitative immunofluorescence on the biopsies pre-virus injection. T cells were hardly noticeable in these tumors while macrophages were abundant. Using a multiplexed TCR-sequencing mRNA-based assay to analyze 18 available paired pre- and post-treatment samples from the trial, we detected increased clonal T cell diversity following treatment with virus. In addition, we are assessing the existence of pre and post treatment neutralizing antibodies and its relationship with survival. Finally, we have performed functional studies using 2 cell lines isolated from patients included in this trials and confronting them with T-cells isolated from peripheral blood of the same patients before and after the treatment with the virus. Information acquired within this clinical study would aid to understand the response of DIPGs to viral therapies and therefore to better tailor this strategy to improve the survival of pediatric brain tumors.