ON-123300 is a potent and multi-targeted kinase inhibitor with potential application for brain tumor chemotherapy. ON123300 strongly inhibits Ark5 and CDK4, as well as growth factor receptor tyrosine kinases such as β-type platelet-derived growth factor receptor (PDGFRβ). ON123300 inhibited U87 glioma cell proliferation and reduced phosphorylation of Akt, yet it also unexpectedly induced Erk activation, both in a dose- and time-dependent manner that subsequently was attributed to relieving Akt-mediated C-Raf S259 inactivation and activating a p70S6K-initiated PI3K-negative feedback loop. ON123300 demonstrated high brain and brain tumor accumulation and favorable pharmacokinetic characteristics.

TAK-243 (MLN7243) is a small molecule inhibitor of ubiquitin-activating enzyme (UAE), with potential antineoplastic activity, which was developed by Takeda Oncology, Millennium. MLN7243 binds to and inhibits UAE, which prevents both protein ubiquitination and subsequent protein degradation by the proteasome. This inhibits tumor cell proliferation and survival. UAE, also called ubiquitin E1 enzyme (UBA1; E1), is more active in cancer cells than in normal, healthy cells. Currently, TAK-243 is in phase I clinical trial evaluating safety, tolerability, pharmacokinetics, pharmacodynamics against advanced malignant solid tumors phase.