In this study, we used NMR spectroscopy to search for potential non-invasive biomarkers for the effects of the dual pan-Class I PI3K/mTOR inhibitor PI-103 [14]–[16] and the pan–Class I PI3K inhibitor GDC-0941 lacking significant mTOR activity [14]–[16] in two pediatric glioblastoma cell lines, SF188 and KNS42, in vitro. Here, PIK3CA is linked to glioblastoma.