In our work, we hypothesize that NRP1 inhibition with this new peptidomimetic compound could improve radiotherapy treatment by targeting medulloblastoma stem-like cells, and we evaluated the effect of NRP1 inhibition with MR438 concomitant with RT in 3 subgroup MB models (DAOY, D283-Med and D341-Med) by in vitro experiments on stem-like cells, as well as on in vivo heterotopic and orthotopic xenografts. This evidence concerns the gene NRP1 and medulloblastoma.