Cobimetinib and trametinib inhibit platelet MEK but do not cause platelet dysfunction

Intracranial hemorrhage caused by dabrafenib and trametinib therapy for metastatic melanoma

Although generally well tolerated compared with chemotherapy, molecular targeted therapy used in metastatic melanoma may be associated with life-threatening toxicity. We report the case of a patient with metastatic melanoma treated by dabrafenib plus trametinib who developed intracranial hemorrhage. Physicians should be aware of this rare but life-threatening adverse event of B-rapidly accelerated fibrosarcoma (BRAF) and mitogen-activated protein kinase kinase (MEK) inhibitors. However, they should be also careful about the bleeding origin, which can prove to be a new onset of melanoma metastasis or anticoagulation overdose, or even an uncontrolled arterial hypertension.

Allosteric crosstalk in modular proteins: Function fine-tuning and drug design

Modular proteins are regulatory proteins that carry out more than one function. These proteins upregulate or downregulate a biochemical cascade to establish homeostasis in cells. To switch the function or alter the efficiency (based on cellular needs), these proteins require different facilitators that bind to a site different from the catalytic (active/orthosteric) site, aka 'allosteric site', and fine-tune their function. These facilitators (or effectors) are allosteric modulators. In this Review, we have discussed the allostery, characterized them based on their mechanisms, and discussed how allostery plays an important role in the activity modulation and function fine-tuning of proteins. Recently there is an emergence in the discovery of allosteric drugs. We have also emphasized the role, significance, and future of allostery in therapeutic applications.

MEK inhibition reduced vascular tumor growth and coagulopathy in a mouse model with hyperactive GNAQ

Activating non-inherited mutations in the guanine nucleotide-binding protein G(q) subunit alpha (GNAQ) gene family have been identified in childhood vascular tumors. Patients experience extensive disfigurement, chronic pain and severe complications including a potentially lethal coagulopathy termed Kasabach-Merritt phenomenon. Animal models for this class of vascular tumors do not exist. This has severely hindered the discovery of the molecular consequences of GNAQ mutations in the vasculature and, in turn, the preclinical development of effective targeted therapies. Here we report a mouse model expressing hyperactive mutant GNAQ in endothelial cells. Mutant mice develop vascular and coagulopathy phenotypes similar to those seen in patients. Mechanistically, by transcriptomic analysis we demonstrate increased mitogen activated protein kinase signaling in the mutant endothelial cells. Targeting of this pathway with Trametinib suppresses the tumor growth by reducing vascular cell proliferation and permeability. Trametinib also prevents the development of coagulopathy and improves mouse survival.

Characterization of the impact of immune checkpoint inhibitors on platelet activation and aggregation

Immune checkpoint inhibitors (ICIs) are effective oncological drugs which block cellular check-point receptors typically targeted by tumor immune evasion strategies. Despite their benefits, clinicians have reported treatment-associated thromboembolism during ICI therapy in recent years. Though several theories on this ICI-associated pathogenesis exist, the direct effects of ICIs on platelets remains unknown. We therefore investigated the potential direct and indirect effect of PD-1, PD-L1 and CTLA-4-targeting ICIs on platelet functionality in multifaceted in vitro experiments. Interestingly, we could not observe a clear effect of ICI on platelet aggregation and primary hemostasis in whole blood and platelet concentrate-based assays. Furthermore, the presence of ICIs in toll-like receptor stimulation had no significant impact on platelet surface marker expression. In a second approach, we investigated the indirect immunological impact of ICIs on platelet activation by exposing platelets to supernatants from ICI- and Staphylococcal enterotoxin B-exposed PBMCs. Whereas ICIs affected IL-2 levels in supernatants, we could not detect clear differences in the secretion of pro-thrombogenic factors and platelet responses. The obtained data suggest that the direct influence of ICIs on platelet activation or the influence of altered T cell function on platelet activation cannot be considered a major factor in the development of thrombotic events.

Outcomes of Patients with Metastatic Melanoma-A Single-Institution Retrospective Analysis

Background: This study assessed risk factors and the results of treatment with anti-PD-1 antibodies and BRAF/MEK inhibitors for advanced malignant melanoma. Methods: A retrospective analysis was performed on 52 patients treated with immunotherapy and BRAF/MEK inhibitors for disseminated malignant melanoma. Results: The median follow-up was 31 months (6−108 months). The median PFS1 was 6 months (1−44 months). Second-line systemic treatment was applied in 27 patients (52%). The median PFS2 was 2 months (0−27 months), and the median OS was 31 months (6−108 months). Among the analyzed risk factors, only the presence of the BRAF mutation was statistically significant for disease recurrence after surgery. In patients undergoing anti-BRAF/MEK therapy, the median PFS1 was 7 months, and in patients undergoing mono-immunotherapy, 4 months. The 12- and 24-month PFS1 rates in the group treated with BRAF inhibitors were 29 and 7%, respectively, and in patients treated with mono-immunotherapy 13 and 0%, respectively (Z = 1.998, p = 0.04). The type of treatment used had no effect on OS (Z = 0.237, p > 0.05). Conclusion: Patients with the V600 mutation should be closely monitored. In the event of disease recurrence, treatment with BRAF/MEK inhibitors should be considered. The type of treatment used has no effect on OS.

Severe Epistaxis Secondary to Dabrafenib and Trametinib Toxicity in Non-small Cell Lung Carcinoma With Small Bowel Metastasis

BRAF mutations are estimated to be present in 2-4% of non-small cell lung carcinoma (NSCLC) cases. BRAF inhibitor (dabrafenib) and MEK inhibitor (trametinib) are currently approved to treat NSCLC harboring the BRAF V600E mutation. However, the use of this new combined targeted therapy can be associated with severe and life-threatening toxicities.

Here, we describe the case of a 77-year-old male with a history of BRAF-positive lung adenocarcinoma with metastasis to the brain, adrenals, and small bowel (jejunum), currently on dual therapy with dabrafenib and trametinib, who presented with refractory epistaxis. The dual therapy regimen was started one month prior to his presentation. After initial stabilization with anterior nasal packing, intravenous and nebulized tranexamic acid (TXA) in the emergency department (ED), he suddenly developed respiratory decompensation. He needed emergent intubation for acute hypoxic respiratory failure and airway protection secondary to profuse bleeding. He was extubated 24 hours later as the epistaxis was manageable, and the nasal packing was removed. Shortly after extubating, he started coughing copious amounts of blood and developed respiratory distress with stridor requiring re-intubation. A large blood clot was noted to be partially occluding the vocal cords on laryngoscopy and was removed during intubation. An emergent flexible fiberoptic bronchoscopy was performed with the retrieval of a large blood clot extending from the oropharynx down into the distal trachea. There was no evidence of acute bleeding within the lung after the clot was removed. Workup to explore the cause of his bleeding included a coagulation profile, which was unrevealing. His bleeding was most likely consistent with a side effect of his treatment with dabrafenib and trametinib.

Life-threatening bleeding has been reported as a side effect of the combination therapy with dabrafenib and trametinib in metastatic melanoma. Also, in the phase 2 clinical trial (BRF113928) of dabrafenib plus trametinib in patients with previously untreated BRAF V600E-mutant metastatic NSCLC, 3.2% of subjects developed a grade III or IV hemorrhage. Our case aims to raise physicians' awareness of one of the significant side effects of this combination therapy especially since this combination is being used more frequently and now also in lung cancer.

Benzophenone Compounds, from a Marine-Derived Strain of the Fungus Pestalotiopsis neglecta, Inhibit Proliferation of Pancreatic Cancer Cells by Targeting the MEK/ERK Pathway

Pancreatic cancer, which has an extremely poor prognosis, is one of the most fatal human cancers. Chemotherapy is the main palliative treatment for advanced cancer patients and also plays an indispensable role in postoperative treatments for surgical patients. Therefore, there is an urgent need to develop more innovative anticancer drugs to fight against this fatal disease. Here, we investigate the potential of benzophenone derivatives, obtained from a marine-derived strain of the fungus Pestalotiopsis neglecta, as antiproliferative lead compounds for the treatment of pancreatic cancer. The compounds, seven new (1-7) and two known (8 and 9) halogenated benzophenone derivatives, were obtained by bioactivity-guided fractionation from the cultures of Pestalotiopsis neglecta. The structures were defined by spectroscopic methods including X-ray crystallographic analysis. Using the commonly used pancreatic cancer cell line PANC-1, 2 and 4 were found to suppress cell proliferation and induce apoptosis in the low micromolar range of 7.6 and 7.2 μM, respectively. Mechanistically, benzophenone derivatives not only inhibit MEK activity in the cytoplasm but also suppress ERK activity in the cytoplasm and nucleus. An in silico study suggests that benzophenone derivatives could potentially inhibit MEK activity by binding to the allosteric pocket in MEK. Benzophenones could serve as new lead compounds for the treatment of pancreatic cancer.

Rationale for a Combination Therapy Consisting of MCL1- and MEK-Inhibitors in Acute Myeloid Leukemia

Amplification and overexpression of the myeloid cell leukemia differentiation protein MCL1 and the murine double minute protein MDM2 have been reported in various human tumors as well as hematological malignancies including acute myeloid leukemia (AML). While MCL1 is an anti-apoptotic member of the BCL-2 family proteins, MDM2 is an important cellular inhibitor of the p53 tumor suppressor. The key oncogene in AML is the FLT3 growth factor receptor gene. FLT3 signaling pathways including the MAPK cascade (RAS-RAF-MEK-ERK) are highly active in AML cells, leading to induced protein translation and cell proliferation as well as reduced apoptosis. Consequently, combined administration of MCL1-, MDM2-, and MEK-inhibitors may present a promising anti-leukemic treatment strategy. Here, we assessed the MCL1-antagonist S63845, the MDM2-inhibitor HDM201, and the MEK1/2-inhibitor trametinib as single agents and in combination in a variety of AML cell lines and mononuclear cells isolated from patients with hematological malignancies centered on myeloid leukemia, some lymphatic leukemia, as well as some lymphomas, for their ability to induce apoptosis and cell death. We observed a considerably varying anti-leukemic efficacy of the MCL1-inhibitor S63845 and the MEK1/2-inhibitor trametinib. Hematological cells with susceptibility to the single compounds as well as to the combined treatment were defined by elevated MCL1- and MEK-protein levels, independent of the mutational status of FLT3 and TP53. Our data indicate that hematological cells with elevated MCL1- and MEK-protein levels are most sensitive to the combined treatment with S63845 and trametinib. MCL1- and MEK1/2-protein expression may be valid biomarkers for treatment response to S63845 and trametinib, respectively.