PIK3CD and cancer: The promise of class I PI3Ks as a molecular target family for cancer therapy has led to the design and development of a number of small molecule drugs that have advanced into clinical development.7 At the time of writing, the p110δ-targeted inhibitor idelalisib (Zydelig) is the sole approved PI3K inhibitor, which is specifically used for the treatment of hematological malignancies, whereas the majority of PI3K-targeted agents currently in clinical development for solid tumor therapy are pan-p110 isoform inhibitors.