A novel pan-RAS inhibitor for malignant peripheral nerve sheath tumors.

Abstract

e23531 Background: Malignant Peripheral Nerve Sheath Tumors (MPNST) are a rare but deadly form of sarcoma originating from the Schwann cell compartment. They are usually driven by loss of function of the NF1 tumor suppressor. This can happen spontaneously but is also the cause of disease in the inheritable syndrome of Neurofibromatosis. Neurofibromatosis is a member of the family of genetic diseases known as “Rasopathies” and is one of the most common inherited neurological disorders. NF1 serves as an important negative regulator or GAP for the RAS oncoprotein. Loss of function of NF1 thus results in the upregulation of non-mutant RAS activity and this appears to be a driving event in the disease. Therapeutic options remain poor. An obvious approach to effective treatment would be targeted therapy directed at non-mutant Ras proteins. There are currently no approved pan-RAS inhibitors. We have developed a small molecule pan-RAS inhibitor which binds directly to all forms of RAS. It acts to block the ability of RAS and to bind and signal through its effectors. It is active in vitro and in vivo against multiple models of MPNST. Methods: In silico screening of a virtual compound library was performed to identify an initial candidate inhibitor. Iterative rounds of Medicinal Chemistry informed by structural modeling and bioassay in 3D vs 2D growth assays were performed to identify an enhanced activity derivative. Target binding was confirmed by Microscale Thermophoresis and NMR. RAS/RAF complex status was measured by co-immunoprecipitation of the endogenous proteins. Ras signaling was assayed by Western analysis of Phospho-ERK and RAL-GTP pull down assays. In vitro activity was measured using 3D soft agar assays. In vivo activity was measured by ip or po administration against MPNST pdx systems. Results: The current lead, designated RAS-F binds all three main isoforms of RAS at low uM kd and modulates the RAS effector domain in NMR studies. It suppresses RAS signaling pathways in transient assays and suppresses MPNST tumor cell growth in soft agar with IC50s ̃ 250nM. It suppresses MPNST pdx growth. Conclusions: We have developed a pre-clinical pan-RAS inhibitor that is active in vitro and in vivo against MPNST cancer models. The agent also has potential uses against non-tumor manifestations of Neurofibromatosis such as Plexiform and Cutaneous neurofibromas. Funding: NIH 5U01HL127518-03, Kentucky Lung Cancer Research Program CDMRP NF180094 (GJC). Qualigen Therapeutics LLC (GJC, JOT).