A pan-RAF inhibitor LY3009120 inhibits necroptosis by preventing phosphorylation of RIPK1 and alleviates dextran sulfate sodium-induced colitis.

A dramatic increase in the incidence of inflammatory bowel disease (IBD) has been observed in the past two decades, mainly in developed countries and also in developing regions. Necroptosis has been found to play an important role in the pathogenesis of IBD, suggesting its inhibitors are promising in clinic. However, clinical drugs targeting necroptosis are seriously lacking. Through screening a clinical compound library that contains 611 inhibitors, a pan-RAF inhibitor LY3009120 was found to be promising as a necroptosis inhibitor. LY3009120 inhibited necroptosis in vitro, and its inhibition against necroptosis was independent of its well-known activity to inhibit RAF. Surprisingly, LY3009120 prevented phosphorylation of receptor interacting serine/threonine kinase 1 (RIPK1) and subsequently phosphorylation of receptor interacting serine/threonine kinase 3 (RIPK3) and mixed lineage kinase domain like pseudokinase (MLKL) which happened during necroptosis. In vivo, LY3009120 significantly alleviated dextran sulfate sodium (DSS)-induced colitis as indicated by prevention of body weight loss, colon shortening, and decreased mortality. Furthermore, LY3009120 inhibited necroptosis of intestinal epithelial cells (IECs) and prevented intestinal barrier function loss. Consistently, LY3009120 decreased DSS-induced colonic inflammation, as indicated by decreased infiltration of macrophages and neutrophils, and decreased colonic TNF-α, IL-6, and IL-1ß level in DSS treated mice. These results indicate that an anti-cancer pan-RAF inhibitor LY3009120 is a necroptosis inhibitor and may serve as a potential therapeutic drug for colitis.

Targeting oncogenic Raf protein-serine/threonine kinases in human cancers.

The Ras-Raf-MEK-ERK signal transduction cascade is arguably the most important oncogenic pathway in human cancers. Ras-GTP promotes the formation of active homodimers or heterodimers of A-Raf, B-Raf, and C-Raf by an intricate process. These enzymes are protein-serine/threonine kinases that catalyze the phosphorylation and activation of MEK1 and MEK2 which, in turn, catalyze the phosphorylation and activation of ERK1 and ERK2. The latter catalyze the regulatory phosphorylation of dozens of cytosolic and nuclear proteins. The X-ray crystal structure of B-Raf-MEK1 depicts a face-to-face dimer with interacting activation segments; B-Raf is in an active conformation and MEK1 is in an inactive conformation. Besides the four traditional components in the Ras-Raf-MEK-ERK signaling module, scaffolding proteins such as Kinase Suppressor of Ras (KSR1/2) play an important role in this signaling cascade by functioning as a scaffold protein. RAS mutations occur in about 30% of all human cancers. Moreover, BRAFV600E mutations occur in about 8% of all cancers making this the most prevalent oncogenic protein kinase. Vemurafenib and dabrafenib are B-RafV600E inhibitors that were approved for the treatment of melanomas bearing the V600E mutation. Coupling MEK1/2 inhibitors with B-Raf inhibitors is more effective in treating such melanomas and dual therapy is now the standard of care. Vemurafenib and cobimetanib, dabrafenib and trametinib, and encorafenib plus binimetinib are the FDA-approved combinations for the treatment of BRAFV600E melanomas. Although such mutations occur in other neoplasms including thyroid, colorectal, and non-small cell lung cancers, these agents are not as effective in treating these non-melanoma neoplasms. Vemurafenib and dabrafenib produce the paradoxical activation of the MAP kinase pathway in wild type BRAF cells. The precise mechanism for this activation is unclear, but drug-induced Raf activating side-to-side dimerization appears to be an essential step. Although 63%-76% of all people with advanced melanoma with the BRAF V600E mutation derive clinical benefit from combination therapy, median progression-free survival lasts only about nine months and 90% of patients develop resistance within one year. The various secondary resistance mechanisms include NRAS or KRAS mutations (20%), BRAF splice variants (16%), BRAFV600E/K amplifications (13%), MEK1/2 mutations (7%), and non-MAP kinase pathway alterations (11%). Vemurafenib and dabrafenib bind to an inactive form of B-Raf (αC-helixout and DFG-Din) and are classified as type I½ inhibitors. LY3009120 and lifirafenib, which are in the early drug-development stage, bind to a different inactive form of B-Raf (DFG-Dout) and are classified as type II inhibitors. Besides targeting B-Raf and MEK protein kinases, immunotherapies that include ipilimumab, pembrolizumab, and nivolumab have been FDA-approved for the treatment of melanomas. Current clinical trials are underway to determine the optimal usage of targeted and immunotherapies.

Cross-Species Comparison of the Pan-RAF Inhibitor LY3009120's Anti-Tumor Effects in Equine, Canine, and Human Malignant Melanoma Cell Lines.

Malignant melanomas (MMs) are the abnormal proliferation of melanocytes and are one of the lethal skin cancers in humans, equines, and canines. Accordingly, MMs in companion animals can serve as naturally occurring animal models, completing conventional cancer models. The common constitutive activation of the MAPK and PI3K pathways in MMs has been described in all three species. Targeting the related pathways is considered a potential option in comparative oncologic approaches. Herein, we present a cross-species comparative analysis exposing a set of ten melanoma cell lines (one human, three equine, and six canine) derived from primary tumors or metastasis to a pan-RAF and RAF dimer inhibitor (LY3009120). Cellular response (proliferation, biomass, metabolism, early and late apoptosis/necrosis, and morphology) and the presence of pathogenic single-nucleotide variants (SNVs) within the mutational hotspot genes BRAF exon 11 and 15, NRAS exon 2 and 3, KRAS exon 2, and KIT exon 11 were analyzed. This study showed that equine malignant melanoma (EMM) cells (MelDuWi) harbor the KRAS p.Q61H mutation, while canine malignant melanoma (CMM) cells (cRGO1 and cRGO1.2) carry NRAS p.G13R. Except for EMM metastasis cells eRGO6 (wild type of the above-mentioned hotspot genes), all melanoma cell lines exhibited a decrease in dose dependence after 48 and 72 h of exposure to LY3009120, independent of the mutation hotspot landscape. Furthermore, LY3009120 caused significant early apoptosis and late apoptosis/necrosis in all melanoma cell lines except for eRGO6. The anti-tumor effects of LY3009120 were observed in nine melanoma cell lines, indicating the potential feasibility of experimental trials with LY3009120. The present study reveals that the irradiation-resistant canine metastasis cells (cRGO1.2) harboring the NRAS p.G13R mutation are significantly LY3009120-sensitive, while the equine metastases-derived eRGO6 cells show significant resistance to LY3009120, which make them both valuable tools for studying resistance mechanisms in comparative oncology.

Evaluation of Pan-RAF Inhibitor LY3009120 on Human Uveal Melanoma Cell Line 92-1.

BACKGROUND/AIM: Uveal melanoma (UM) represents a prevailing primary intraocular malignancy, with a limited median overall survival among metastatic patients, and most tumors lack RAF/RAS mutations. The pan-RAF inhibitor LY3009120 has demonstrated valuable anti-tumor effects in a wide range of RAF/RASmut and wild-type (WT) tumor models. This study aimed to evaluate the antitumor effect of LY3009120 on 92-1 UM cell line. MATERIALS AND METHODS: The effect of the pan-RAF inhibitor LY3009120 on cell proliferation, metabolic activity, biomass, early and late apoptosis/necrosis, and morphology was characterized in vitro (0.1-5 µM for 48 h/72 h). Furthermore, targeted panel sequencing was used to characterize the mutational landscape of the human 92-1 UM cell line. RESULTS: LY3009120 showed a significant concentration-dependent anti-proliferative effect on 92-1 cells. Cell proliferation and viability were significantly reduced at the lowest effective concentration of 0.5 µM (at 48 and 72 h, p<0.001). Furthermore, LY3009120 caused significant early apoptosis and late apoptosis/necrosis in 92-1 cells at 5 µM. Except for TP53, NGS showed that all 49 additional analysed genes (Oncomine myeloid panel) of 92-1 were wild-type, including BRAF, NRAS, and KRAS. CONCLUSION: The pan-RAF inhibitor LY3009120 demonstrated a significant anti-tumor effect on human UM cell line 92-1 independent of the molecular BRAF and RAS mutational status.

Antitumor Effects of Pan-RAF Inhibitor LY3009120 Against Lung Cancer Cells Harboring Oncogenic BRAF Mutation.

BACKGROUND/AIM: The therapeutic strategy for patients with non-small-cell lung cancer (NSCLC) harboring the BRAF non-V600E mutation has not been established. LY3009120, a newly discovered pan-RAF inhibitor, has shown strong antitumor effects in cancers with various BRAF genotypes. This study investigated the antitumor effects of LY3009120 in NSCLC cells harboring the BRAF non-V600E mutation. MATERIALS AND METHODS: We examined the antitumor effects of LY3009120 by MTS assay and flow cytometry. We analyzed the expression status of proteins by western blot. The mouse xenograft models were used for the in vivo experiments. RESULTS: LY3009120 suppressed BRAF-related downstream pathway molecules and induced cleavage of poly ADP-ribose polymerase in all examined NSCLC cell lines. LY3009120 also inhibited in vivo tumor growth in NSCLC cells harboring the BRAF non-V600E mutation. CONCLUSION: LY3009120 is a potent therapeutic agent for patients with BRAF non-V600E mutant NSCLC.

Obatoclax and LY3009120 Efficiently Overcome Vemurafenib Resistance in Differentiated Thyroid Cancer.

Although the prognosis of differentiated thyroid cancer (DTC) is relatively good, 30-40% of patients with distant metastases develop resistance to radioactive iodine therapy due to tumor dedifferentiation. For DTC patients harboring BRAFV600E mutation, Vemurafenib, a BRAF kinase inhibitor, has dramatically changed the therapeutic landscape, but side effects and drug resistance often lead to termination of the single agent treatment. In the present study, we showed that either LY3009120 or Obatoclax (GX15-070) efficiently inhibited cell cycle progression and induced massive death of DTC cells. We established that BRAF/CRAF dimerization was an underlying mechanism for Vemurafenib resistance. LY3009120, the newly discovered pan-RAF inhibitor, successfully overcame Vemurafenib resistance and suppressed the growth of DTC cells in vitro and in vivo. We also observed that expression of anti-apoptotic Bcl-2 increased substantially following BRAF inhibitor treatment in Vemurafenib-resistant K1 cells, and both Obatoclax and LY3009120 efficiently induced apoptosis of these resistant cells. Specifically, Obatoclax exerted its anti-cancer activity by inducing loss of mitochondrial membrane potential (ΔΨm), dysfunction of mitochondrial respiration, reduction of cellular glycolysis, autophagy, neutralization of lysosomes, and caspase-related apoptosis. Furthermore, the cancer killing effects of LY3009120 and Obatoclax extended to two more Vemurafenib-resistant DTC cell lines, KTC-1 and BCPAP. Taken together, our results highlighted the potential value of LY3009120 for both Vemurafenib-sensitive and -resistant DTC and provided evidence for the combination therapy using Vemurafenib and Obatoclax for radioiodine-refractory DTC.