AKT1 and central nervous system neoplasm: In 2015, Kilburn et al. [154] published a study evaluating the MTD and toxicity of enzastaurin, a potent oral serine/threonine kinase inhibitor targeting protein kinase Cβ (PKCβ) and the phosphoinositide 3-kinase (PI3K)/ Akt pathways [155,156], in 33 patients under 22 years of age with histologically confirmed recurrent, progressive, or refractory primary CNS tumors.