INFORM2 Study Uses Nivolumab and Entinostat in Children and Adolescents With High-risk Refractory Malignancies

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Compared to adult cancers, most pediatric cancers carry a relatively low mutational burden. However, a small fraction of pediatric tumors in the INFORM registry cohort display a higher mutational burden. Truly hypermutated tumors, e.g. in the context of rare cancer predisposition syndromes, are repo...

Compared to adult cancers, most pediatric cancers carry a relatively low mutational burden. However, a small fraction of pediatric tumors in the INFORM registry cohort display a higher mutational burden. Truly hypermutated tumors, e.g. in the context of rare cancer predisposition syndromes, are reported to respond well to immune checkpoint inhibition. In addition to hypermutation, increased PD-L1 expression is associated with clinical responses to checkpoint inhibition. Increased PD-L1 mRNA expression is observed in a small fraction of pediatric patients in the INFORM registry cohort independent from mutational load. We hypothesize that pediatric tumors with a high mutational burden and/or high PD-L1 expression will respond to checkpoint inhibition. HDAC inhibition (HDACi) modifies T-cell regulation and can augment response to checkpoint inhibition by reducing the number of myeloid-derived suppressor cells and creating an immunogenic tumor microenvironment including induction of MHCI and neo-antigens. In vitro and in vivo models showed enhanced anti-tumor activity of the combination of checkpoint inhibition and HDACi compared to either agent alone. This provides a strong rationale to combine these drug classes. Furthermore, MYC- or NMYC-driven (referred to as MYC(N)) malignancies like very high-risk medulloblastomas or very high-risk neuroblastomas still have a dismal outcome. MYC is not only reported to upregulate PD-L1 and thereby a possible biomarker for checkpoint inhibition but also very compelling recent preclinical data strongly suggests that HDAC inhibitors are active against MYC amplified medulloblastoma in vitro and in vivo. In NMYC amplified neuroblastoma cell lines similar observations were made in vitro. Taken together, our results suggest that MYC(N)-driven tumors depend on HDAC and we hypothesize that MYC(N) status can serve as a biomarker for response prediction to a combinatorial treatment of checkpoint inhibition and HDAC inhibition. Pediatric patients aged 6-21 years with refractory/relapsed/progressive high-risk malignancies with a high mutational load (group A), with high PD-L1 mRNA expression (group B), with MYC(N) amplification (group C) and with a low mutational load, low PD-L1 mRNA expression and no MYC(N) amplification (Biomarker low group D) are eligible for this trial. Phase I determines the recommended phase 2 dose (RP2D) for the combination of the HDACi entinostat and the checkpoint inhibitor nivolumab for the age groups 6-11 and 12-21 years, respectively. Phase II investigates activity in 4 groups A, B, C, D. The duration of treatment is 12 cycles (1 cycle = 28 days), preceded by 1 priming week. In addition, a comprehensive accompanying research program investigates PD biomarkers for immune checkpoint and HDAC inhibition. Clinical trials investigating the combination of nivolumab and entinostat in children have not been reported so far.

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