Pilaralisib (XL147, SAR245408) is a potent and highly selective inhibitor of class I phosphatidylinositol 3-kinase (PI3K) (α, β, γ, and δ). In cellular assays, XL147 inhibits the formation of PIP3 in the membrane, and inhibits phosphorylation of AKT, p70S6K, and S6 in multiple tumor cell lines with diverse genetic alterations affecting the PI3K pathway. In a panel of tumor cell lines, XL147 inhibits proliferation with a wide range of potencies, with evidence of an impact of genotype on sensitivity. Repeat-dose administration of XL147 results in significant tumor growth inhibition in multiple human xenograft models in nude mice. Pilaralisib, was being developed by Exelixis and its licensee, Sanofi (formerly sanofi-aventis), for the treatment of solid tumours. However, the product was not listed on Sanofi's early stage pipeline as of end of July 2015 and there have been no recent reports on development identified.