In addition to pharmacological inhibition of XBP1, we confirmed a similar effect of BEZ235 upon genetic loss of Xbp1, suggesting that an interplay between PI3K/mTOR signalling and IRE1α‐XBP1 promotes survival of pre‐B NRASG12D ALL cells and that these cells in the absence of active XBP1 are particularly vulnerable to BEZ235 treatment. This evidence concerns the gene MTOR and acute lymphoblastic leukemia.