Small molecules bind human mTOR protein and inhibit mTORC1 specifically
Inhibition ofmTORactivity (mechanistic target of rapamycin) is an anti-cancer therapeutic strategy. mTOR participates in two functional complexes, mTORC1 and mTORC2. Since mTORC1 is specifically activated in multiple tumors, novel molecules that inhibit mTORC1 could be therapeutically important. To identify potentially novel modulators of mTOR pathways, we screened 1600 small molecule human drugs for mTOR protein binding, using novel biolayer interferometry technology. We identified several small molecules that bound to mTOR protein in a dose-dependent manner, on multiple chemical scaffolds. As mTOR participates in two major complexes, mTORC1 and mTORC2, the functional specificities of the binders were measured by S6Kinase and Akt phosphorylation assays. Three novel ‘mTOR general’ binders were identified,carvedilol,testosterone propionate, andhydroxyprogesterone, which inhibited both mTORC1 and mTORC2. By contrast, thepiperazinedrugcinnarizinedose-dependently inhibited mTORC1 but not mTORC2, suggesting it as a novel mTORC1-specific inhibitor. Some of cinnarizine’s chemical analogs also inhibited mTORC1 specifically, whereas others did not. Thus we report the existence of a novel target for some relatedpiperazinesincluding cinnarizine andhydroxyzine, i.e. specific inhibition of mTORC1 activity. Since mTOR inhibition is a general anti-cancer strategy, and mTORC1 is specifically activated in some tumors, we suggest the piperazine scaffold, including cinnarizine and hydroxyzine, could be proposed for rational therapy in tumors in which mTORC1 is specifically activated. Related piperazines have shown toxicity to cancer cells in vitro as single agents and in combination chemotherapy. Thus piperazine-based mTOR inhibitors could become a novel chemotherapeutic strategy.
Glioblastoma (GBM) is an aggressive tumor of the brain, with an average post-diagnosis survival of 15 months. GBM stem cells (GBMSC) resist the standard-of-care therapy, temozolomide, and are considered a major contributor to tumor resistance. Mammalian target of rapamycin Complex 1 (mTORC1) regulates cell proliferation and has been shown by others to have reduced activity in GBMSC. We recently identified a novel chemical series of human-safe piperazine-based brain-penetrant mTORC1-specific inhibitors. We assayed the piperazine-mTOR binding strength by two biophysical measurements, biolayer interferometry and field-effect biosensing, and these confirmed each other and demonstrated a structure–activity relationship. As mTORC1 is altered in human GBMSC, and as mTORC1 inhibitors have been tested in previous GBM clinical trials, we tested the killing potency of the tightest-binding piperazines and observed that these were potent GBMSC killers. GBMSCs are resistant to the standard-of-care temozolomide therapy, but temozolomide supplemented with tight-binding piperazine meclizine and flunarizine greatly enhanced GBMSC death over temozolomide alone. Lastly, we investigated IDH1-mutated GBMSC mutations that are known to affect mitochondrial and mTORC1 metabolism, and the tight-binding meclizine provoked ‘synthetic lethality’ in IDH1-mutant GBMSCs. In other words, IDH1-mutated GBMSC showed greater sensitivity to the coadministration of temozolomide and meclizine. These data tend to support a novel clinical strategy for GBM, i.e., the co-administration of meclizine or flunarizine as adjuvant therapy in the treatment of GBM and IDH1-mutant GBM.
A tyrosine kinase inhibitor used to treat a number of leukemias, myelodysplastic/myeloproliferative disease, systemic mastocytosis, hypereosinophilic syndrome, dermatofibrosarcoma protuberans, and gastrointestinal stromal tumors.
An antifungal agent used for the treatment of various fungal infections in immunocompromised and non-immunocompromised patients, such as pulmonary and extrapulmonary blastomycosis, histoplasmosis, and onychomycosis.
An atypical antipsychotic used in the treatment of a wide variety of mood and psychotic disorders, such as schizophrenia, bipolar I, major depressive disorder, irritability associated with autism, and Tourette's syndrome.
A P2Y12 platelet inhibitor used to reduce risk of thrombotic cardiovascular events in unstable angina or non-ST-elevation myocardial infarction (NSTEMI), and in patients with STEMI when managed with either primary or delayed PCI.
NNZ-2591 (cyclo-L-glycyl-L-2-allylproline) is an investigational synthetic analog of cyclic glycine-proline (cGP), a breakdown product of human insulin-like growth factor 1 (IGF-1), that has been chemically modified to increase its half-life,...