Mirdametinib in symptomatic neurofibromatosis type 1 plexiform neurofibromas

Paediatric Strategy Forum for medicinal product development in mitogen-activated protein kinase pathway inhibitors: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

IntroductionKi-ras2 (KRAS) mutation is a common driver of lung cancer, and KRAS-mutated tumors are relatively resistant to radiotherapy. Previously, we demonstrated that mitogen-activated protein kinase (MEK) inhibitors (MEKi) enhanced treatment efficacy by increasing the anti-tumor immune response after radiotherapy in KRAS-mutant tumors. In this study, we explored the potential mechanism underlying the MEKi-mediated increase in anti-tumor immune response.Methods and resultRNA sequencing revealed that the MEKi+radiotherapy combination significantly activated the chemokine signaling pathway. Blocking the C-X-C motif chemokine ligand 10 (CXCL10) receptor reduced T-cell infiltration in vivo. The MEKi+radiotherapy combination increased CXCL10 expression and activated the cyclic GMP–AMP synthase-stimulator of interferon genes (cGAS-STING) pathway in KRAS-mutant lung cell lines. Using a STING inhibitor and cGAS-knockout LLC cells, we showed that CXCL10 production was mediated by the cGAS-STING pathway via nuclear factor kappa B activation. This combination also increased DNA damage and apoptosis in KRAS-mutant lung cancer cell lines, triggering the cGAS-STING pathway. Western blot analysis revealed that MEKi reduced checkpoint kinase 2 phosphorylation after radiotherapy, hindering DNA repair and increasing DNA damage. Flow cytometry revealed that MEKi combined with radiotherapy boosted tumor-infiltrating CD4+ and CD8+ T cells in vivo, enhancing their cytotoxic and secretory functions. In an LLC-bearing mouse model, combining MEKi with varying radiotherapy doses and extending drug holidays revealed that low-dose radiotherapy with MEKi effectively controlled tumor growth.ConclusionOur findings suggest that MEKi activates the cGAS-STING-TANK-binding kinase 1-nuclear factor kappa B-CXCL10 axis post-radiotherapy in KRAS-mutant lung cancer, increasing T-cell infiltration and function, activating anti-tumor immunity, and inhibiting tumor growth. These results indicate the potential for clinical translation.

To the editor, Neurofibromas are relatively common benign tumors that are composed of neuromesenchymal cells, including Schwann cells, perineurial cells, fibroblast and mast cells. Multiple neurofibromas are found as part of neurofibromatosis type I (von Recklinghausen's disease) and neurofibromas are evenly distributed over the body surface. However, as a solitary lesion, a neurofibroma is not associated with neurofibromatosis type I and is common in young adults without a gender preference. Neurofibromas have been known to exhibit a predilection for the trunk and head compared to other body surfaces1. However, in 1949 Herzog2 first reported a plantar neurofibroma in a case of von Recklinghausen's disease. It has been thought that neurofibroma rarely occurs on the palm or sole of the hands or feet. Yamamoto et al.3 reported a plantar neurofibroma as a rare case that was not associated with neurofibromatosis type I. There has been a report of a solitary palmar neurofibroma as a rare case4. Other solitary neurofibromas in uncommon sites have been reported on the male breast5 and the subungual area6-10. In order to investigate the commonly affected sites of solitary neurofibromas, we reviewed the medical records of patients diagnosed with solitary neurofibroma between January 2005 and June 2010. There were 8 patients with solitary neurofibroma and these patients were otherwise healthy. The mean age of the patients was 54-years and the disease duration of solitary neurofibromas ranged from several months to several decades (Table 1). None of the patients had a personal or familial history of neurofibromatosis type I or cafe-au-lait patches. The histopathologic examinations, including S100 stains, were done in all cases for making the differential diagnosis. The histopathologic examination showed unencapsulated tumors in the dermis and the tumors were composed of a fine fibrillary lattice of haphazardly arranged slender spindle cells that showed S100 positivity. As was previously known, there was no gender difference. Interestingly, tumors on the palm and sole, which are considered to be uncommon sites of solitary neurofibroma, were observed in each case (Fig. 1A, B). There was also a case of solitary neurofibroma on the lower lip (Fig. 1C). We believe that these results necessitate the investigation of predilection sites of neurofibromas. Fig. 1 (A) A solitary, dome-shaped papule on the right sole in case No. 4. (B) A 0.5×0.5 cm sized, soft, dome-shaped papule on the left palm in case No. 7. (C) An obliquely arranged, 1×3 cm sized, rubbery nodule on the lower lip in case No. 8. ... Table 1 Gender, age, disease duration and locations of solitary neurofibromas (2005~2010) A previous report evaluated the electron microscopic findings of a solitary subungual neurofibroma, and the electron microscopic findings of a solitary neurofibroma on an exceptional location were in no way inconsistent with those of a neurofibroma on the commonly involved sites6. The histologic findings of our patients were also typical for neurofibroma regardless of the body locations of the tumors. Although several cases of solitary neurofibromas on uncommon sites have been reported, we concluded that neither a predilection site of neurofibroma nor an uncommon site exists for solitary neurofibromas. In our study, the mean age of patients with a solitary neurofibroma (54-years-old) was older than the previously reported age of young adults1. The pathogenesis of isolated solitary neurofibromas is still unclear and further studies on solitary neurofibroma with a larger number of cases are needed.

WNK4 inhibits Ca2 +-activated big-conductance potassium channels (BK) via mitogen-activated protein kinase-dependent pathway

Transforming growth factor (TGF)-beta1 has a biphasic effect on rat intestinal epithelial (RIE) cells. By itself, TGF-beta1 functions as a tumor suppressor by inhibiting the growth, migration and invasion of RIE cells. We show in this study that in conjunction with epidermal growth factor (EGF), TGF-beta1 helped to augment migration, invasion and anchorage-independent growth (AIG) compared to that by EGF alone. EGF plus TGF-beta1 induced a dramatic morphological change characteristic of epithelial-mesenchymal transition (EMT). The mechanism for this enhanced effect of TGF-beta1 and EGF on oncogenic properties was explored by analysis of EGF- and TGF-beta1-mediated signaling pathways and complementary DNA arrays. TGF-beta1 augmented EGF-mediated signaling of mitogen-activated protein kinase (MAPK) and AKT by enhancing and prolonging the activation of the former and prolonging the activation of the latter. Inhibition of MAPK, but not phosphoinositide-3 kinase (PI3K), abolished TGF-beta1 plus EGF-induced EMT and downregulation of E-cadherin at mRNA and protein levels. By contrast, cell migration and invasion were sensitive to inhibition of either MAPK or PI3 kinase. TGF-beta1 plus EGF-induced AIG was significantly more resistant to inhibition of PI3K and MAPK compared to that induced by EGF alone. EGF and TGF-beta1 synergistically induced the expression of a series of proteases including matrix metalloproteinase (MMP) 1 (collagenase), MMP3, MMP9, MMP10, MMP14 and cathepsin. Among them, the expression of MMP1, MMP3, MMP9 and MMP10 was MAPK dependent. Inhibition of the MMPs or cathepsin significantly blocked EGF plus TGF-beta1-induced invasion, but had no effect on colony formation. Phospholipase C (PLC) and Cox2 induced by EGF plus TGF-beta1 also played a significant role in invasion, whereas PLC was also important for colony formation. Our study reveals specific signaling functions and induction of genes differentially required for enhanced effect of EGF- and TGF-beta1-induced oncogenic properties, and helps to explain the tumor-promoting effect of TGF-beta1 in human cancer with elevated expression or activation of TGF-beta1 and receptor protein tyrosine kinases.

Oncolytic virotherapy is one of the cancer treatments that kills cancer cells but leaves normal cells. Furthermore, mitogen-activated protein kinase (MEK) inhibitors boost chimeric antigen receptor expression and increase oncolytic virus entry into tumor cells, and TNF- <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mi mathvariant="normal">α</m:mi> </m:math> {\rm{\alpha }} inhibitors improve the effectiveness of oncolytic virotherapy. We propose a mathematical model of tumor involving oncolytic virotherapy, MEK inhibitors, and TNF- <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mi mathvariant="normal">α</m:mi> </m:math> {\rm{\alpha }} inhibitors. All model properties are performed. Three equilibrium points are computed, and their stabilities are analyzed. Additionally, optimal control is applied to the model to investigate the optimal strategy to reduce the load of tumor cells by using MEK inhibitors, TNF- <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mi mathvariant="normal">α</m:mi> </m:math> {\rm{\alpha }} inhibitors, and oncolytic virotherapy. Numerical results demonstrate that a combination of all three treatments leads to a significant increase in infected tumor cells and macrophages, resulting in more infections of tumor cells and stronger immune response. Both low and high levels of MEK inhibitors are applied in three-treatment combination to explore a role of MEK inhibitors, and a better result in high level of MEK inhibitors case is obtained. Hence, our results confirm that MEK inhibitors could lead to not only more oncolytic virus infection of tumor cells and more immune of macrophages but also limit the virus replication.

Mitogen-activated protein kinase (MEK) inhibitors show promise in treating KRAS-mutated cancers, including colorectal cancer (CRC). However, acquired resistance to MEK inhibitors often results in failure of effective treatment in patients with KRAS-mutated CRC. Here, we demonstrated that basroparib overcomes MEK inhibitor resistance in KRAS-G12V- or -G12D-mutated CRC. This basroparib-mediated sensitization was dependent on the KRAS mutation status and was enhanced specifically in KRAS-G12V- or -G12D-mutated cells. Additionally, when combined with MEK inhibitors, basroparib significantly reduced tumor growth in KRAS-G12V-mutated CRC xenograft models, but not in KRAS-G13D-mutated and -wild-type models. Furthermore, basroparib sensitized KRAS-G12V-mutated CRC cells with acquired resistance to MEK inhibitors. Notably, when combined with MEK inhibitors, basroparib not only suppressed tumor regrowth but also prolonged the survival of tumor models with acquired resistance to MEK inhibitors. Mechanistically, basroparib suppressed Wnt-mediated cancer stemness, a bypass mechanism for acquired resistance to MEK inhibitors in KRAS-mutated CRC. This study provides the first preclinical evidence of the relevance of basroparib in treating CRC with acquired resistance to MEK inhibitors due to APC and KRAS mutations, possibly by reducing the Wnt-mediated cancer stemness.

PURPOSE: Plexiform neurofibromas (PNF) are peripheral nerve sheath tumors that cause significant morbidity in persons with neurofibromatosis type 1 (NF1), yet treatment options remain limited. To identify novel therapeutic targets for PNF, we applied an integrated multi-omic approach to quantitatively profile kinome enrichment in a mouse model that has predicted therapeutic responses in clinical trials for NF1-associated PNF with high fidelity. EXPERIMENTAL DESIGN: Utilizing RNA sequencing combined with chemical proteomic profiling of the functionally enriched kinome using multiplexed inhibitor beads coupled with mass spectrometry, we identified molecular signatures predictive of response to CDK4/6 and RAS/MAPK pathway inhibition in PNF. Informed by these results, we evaluated the efficacy of the CDK4/6 inhibitor, abemaciclib, and the ERK1/2 inhibitor, LY3214996, alone and in combination in reducing PNF tumor burden in Nf1flox/flox;PostnCre mice. RESULTS: Converging signatures of CDK4/6 and RAS/MAPK pathway activation were identified within the transcriptome and kinome that were conserved in both murine and human PNF. We observed robust additivity of the CDK4/6 inhibitor, abemaciclib, in combination with the ERK1/2 inhibitor, LY3214996, in murine and human NF1(Nf1) mutant Schwann cells. Consistent with these findings, the combination of abemaciclib (CDK4/6i) and LY3214996 (ERK1/2i) synergized to suppress molecular signatures of MAPK activation and exhibited enhanced antitumor activity in Nf1flox/flox;PostnCre mice in vivo. CONCLUSIONS: These findings provide rationale for the clinical translation of CDK4/6 inhibitors alone and in combination with therapies targeting the RAS/MAPK pathway for the treatment of PNF and other peripheral nerve sheath tumors in persons with NF1.

Although SB202190 and SB203580 are described as specific p38 MAP kinase inhibitors, several reports have indicated that other enzymes are also sensitive to SB203580. Using a pharmacological approach, we report for the first time that compounds SB202190 and SB203580 were able to directly and selectively interact with a G-protein-coupled receptor, namely the cholecystokinin receptor subtype CCK1, but not with the CCK2 receptor. We demonstrated that these compounds were non-competitive antagonists of the CCK1 receptor at concentrations typically used to inhibit protein kinases. By chimeric construction of the CCK2 receptor, we determined the involvement of two CCK1 receptor intracellular loops in the binding of SB202190 and SB203580. We also showed that two CCK antagonists, L364,718 and L365,260, were able to regulate p38 mitogen-activated protein (MAP) kinase activity. Using a reporter gene strategy and immunoblotting experiments, we demonstrated that both CCK antagonists inhibited selectively the enzymatic activity of p38 MAP kinase. Kinase assays suggested that this inhibition resulted from a direct interaction with both CCK antagonists. Molecular modeling simulations suggested that this interaction occurs in the ATP binding pocket of p38 MAP kinase. These results suggest that SB202190 and SB203580 bind to the CCK1 receptor and, as such, these compounds should be used with caution in models that express this receptor. We also found that L364,718 and L365,260, two CCK receptor antagonists, directly interacted with p38 MAP kinase and inhibited its activity. These findings suggest that the CCK1 receptor shares structural analogies with the p38 MAP kinase ATP binding site. They open the way to potential design of either a new family of MAP kinase inhibitors from CCK1 receptor ligand structures or new CCK1 receptor ligands based on p38 MAP kinase inhibitor structures.

The close association of neurofibromatosis type 1 (NF1) with gliomas raises the question of whether the NF1 gene may be involved in the pathogenesis of sporadic astrocytic brain tumors. However, no frequent mutations within NF1 have been described in these tumors. Recent data on a limited series of gliomas indicate that NF1 expression may even be increased, thereby questioning the role of NF1 as a tumor suppressor in astrocytomas. In the present study, we examined the expression of NF1 in a series of 96 tumors including astrocytomas, meningiomas and plexiform neurofibromas. NF1 RNA transcription levels were compared to those of the reference genes B2M, ACTB and GAPD. The expression of OMGP, which is interposed in the NF1 gene, served as an additional control. NF1 expression did not significantly diverge among different malignancy stages of astrocytomas. As expected, the plexiform neurofibromas showed only very low NF1 expression. A striking finding was the highly variable expression of those genes selected to serve as references. While B2M and ACTB exhibited comparable levels of expression within different grades of astrocytomas and meningiomas, GAPD showed an inverse pattern in these tumors. In conclusion, NF1 expression is strongly reduced in NF1-associated plexiform neurofibromas but not in astrocytic tumors. The significant differences between B2M, ACTB and GAPD transcript levels brings into question the common practice of defining gene expression as a ratio between the transcripts of interest and those of these reference genes.

Neurofibromatosis type 1 (NF1) is an autosomal dominant cancer predisposition syndrome caused by a germline mutation in the NF1 gene. The loss of the second copy of NF1 within Schwann cell precursors (SCPs) contributes to the formation of plexiform neurofibromas (PNs) found in 30-50% of NF1 patients. PNs can progress into malignant peripheral sheath tumors (MPNSTs), an aggressive form of cancer and a leading cause of mortality in NF1 patients. Our lab previously demonstrated frequent chromosome 8 (Chr8) gain in NF1-MPNST patient-derived xenografts (PDX) and patient tumors. To investigate Chr8 gain’s role, we created isogenic NF1-/- iPSC cell lines with and without Chr8 gain. Trisomy 8 fibroblasts were obtained and single-cell cloned to establish wildtype (WT) and Chr8 gain populations. Washington University’s Genome Engineering &amp; Stem Cell Center (GESC@MGI) reprogrammed these cells into human induced pluripotent stem cells (hiPSCs). Using synthetic gRNA and CRISPR/Cas9, NF1 knockout lines were generated. Four iPSC cell lines were differentiated into SCPs, and cell survival and proliferation were assessed using Incucyte cell survival and CellTiter-Glo® Assay. Fluorescence in situ hybridization (FISH) and karyotyping validated the human iPSCs. qPCR revealed high expression of iPSC markers OCT3/4 and SOX2 in all iPSC lines. After differentiation, SCP markers (GAP43 and ITGA4) were upregulated in WT, NF1-/-, and Chr8 gain;NF1-/- SCP lines, demonstrating successful differentiation. Furthermore, Chr8 gain; NF1-/- SCPs displayed enhanced proliferation and increased cell survival compared to WT and NF1-/- SCPs, suggesting improved characteristics in the presence of Chr8 gain. In summary, our research provides insights into Chr8 gain and NF1 loss effects on SCP differentiation, proliferation, and survival. Understanding these molecular mechanisms may contribute to developing targeted therapies for NF1.

3096 Background: Neurofibromatosis type 1(NF1) is an autosomal dominant tumor predisposition syndrome characterized by NF1 gene variants, resulting in over-activation of the RAS pathway. Plexiform neurofibroma (PN) is benign tumors that arise from nerve tissue and are a hallmark feature of NF1. They typically grow along nerves and cause disfigurement, pain, and other complications depending on their location and size. FCN-159, a highly potent and selective inhibitor of MEK1/2 by targeting inhibition of the RAS pathway, holds promise as a therapeutic agent for treating NF1-related PN. Methods: A multi-center, open-label phase 1/2 clinical trial was conducted to assess the safety and efficacy in pediatric patients(pts) with NF1-related PN. Here, we reported the safety and efficacy outcomes observed during phase 2 in pediatric pts, who received FCN-159 at the 5 mg/m2 dose once daily on a continuous basis in a 28-day cycle. Preliminary findings from the phase 1/2 trial were previously disclosed at ASCO 2023. Results: As of November 24, 2023,46 pts enrolled. The median age is 8.0 years (range 2-17). The most frequent PN related complications were disfigurement (69.6%) and pain (63.0%). Median volume of target neurofibroma were 37.7 cm³ (range 2.2-1144.1). Efficacy outcomes are reported for 43 pts (modified intent-to-treat population). With the median follow-up of 15.1 months (range 14.1-16.4), the investigator and Blinded Independent Review Committee (BIRC) assessed ORR were 48.8% and 30.2%, respectively. The mDoR and median mPFS were not reached. Preliminary efficacy data are presented in the table. Among the 16 pediatric subjects with tumor pain at baseline (overall tumor pain NRS≥1) and at least one post-baseline assessment, pain scores decreased by at least 2 points in 81.3% (13/16) pts, and pain scores reduced to 0 points (indicating no pain sensation) in 81.3% (13/16) pts, signifying clinically meaningful improvement. 43 pts (93.5%) experienced TRAEs with grade ≥3 TRAEs occurred in 8 pts (17.4%), including dermatitis acneiform (4.3%), folliculitis (4.3%), pneumonia (2.2%), upper respiratory tract infection (2.2%), ejection fraction decreased (2.2%), and blood creatine phosphokinase increased (2.2%). 2 pts (4.3%) reported treatment-related serious adverse events (one case of dermatitis acneiform and pneumonia each). No TRAEs resulting in dose reduction, discontinuation or death. Conclusions: FCN-159 demonstrated good tolerability and exhibited notable anti-tumor activity in pediatric pts with NF1-related PN. Clinical trial information: NCT04954001 . [Table: see text]

Lung cancer (LC) remains the leading cause of cancer mortality worldwide, and non-small cell LC (NSCLC) represents 80% of all LC. Oxidative stress and inflammation, autophagy, ubiquitin-proteasome system, nuclear factor (NF)-κB, and mitogen activated protein kinases (MAPK) participate in LC pathophysiology. Currently available treatment for LC is limited and in vivo models are lacking. We hypothesized that antioxidants and NF- κB, MAPK, and proteasome inhibitors may exert an antitumoral response through attenuation of several key biological mechanisms that promote tumorigenesis and cancer cell growth. Body and tumor weights, oxidative stress, antioxidants, inflammation, NF-κB p65 expression, fibulins, apoptosis, autophagy, tumor and stroma histology were evaluated in the subcutaneous tumor of LC (LP07 adenocarcinoma) BALB/c mice, with and without concomitant treatment with NF-κB (sulfasalazine), MEK (U0126), and proteasome (bortezomib) inhibitors, and N-acetyl cysteine (NAC). Compared to LC control mice, in subcutanous tumors, the four pharmacological agents reduced oxidative stress markers and tumor proliferation (ki-67). Inflammation and NF-κB p65 expression were attenuated by NF-κB and MAPK inhibitors, and the latter also enhanced apoptotic markers. Catalase was induced by the three inhibitors, while bortezomib also promoted superoxide dismutase expression. NF-κB and MEK inhibitors significantly reduced tumor burden through several biological mechanisms that favored tumor degradation and attenuated tumor proliferation. These two pharmacological agents may enhance the anti-tumor activity of selectively targeted therapeutic strategies for LC. Proteasomal inhibition using bortezomib rather promotes tumor degradation, while treatment with antioxidants cannot be recommended. This experimental model supports the use of adjuvant drugs for the improvement of LC treatment.

Neurofibromatosis type 1 (NF1) plexiform neurofibromas (PNs) are progressive, multicellular neoplasms that cause morbidity and may transform to sarcoma. Treatment of Nf1fl/fl;Postn-Cre mice with cabozantinib, an inhibitor of multiple tyrosine kinases, caused a reduction in PN size and number and differential modulation of kinases in cell lineages that drive PN growth. Based on these findings, the Neurofibromatosis Clinical Trials Consortium conducted a phase II, open-label, nonrandomized Simon two-stage study to assess the safety, efficacy and biologic activity of cabozantinib in patients ≥16 years of age with NF1 and progressive or symptomatic, inoperable PN ( NCT02101736 ). The trial met its primary outcome, defined as ≥25% of patients achieving a partial response (PR, defined as ≥20% reduction in target lesion volume as assessed by magnetic resonance imaging (MRI)) after 12 cycles of therapy. Secondary outcomes included adverse events (AEs), patient-reported outcomes (PROs) assessing pain and quality of life (QOL), pharmacokinetics (PK) and the levels of circulating endothelial cells and cytokines. Eight of 19 evaluable (42%) trial participants achieved a PR. The median change in tumor volume was 15.2% (range, +2.2% to -36.9%), and no patients had disease progression while on treatment. Nine patients required dose reduction or discontinuation of therapy due to AEs; common AEs included gastrointestinal toxicity, hypothyroidism, fatigue and palmar plantar erythrodysesthesia. A total of 11 grade 3 AEs occurred in eight patients. Patients with PR had a significant reduction in tumor pain intensity and pain interference in daily life but no change in global QOL scores. These data indicate that cabozantinib is active in NF1-associated PN, resulting in tumor volume reduction and pain improvement.

Increased cyclooxygenase‐2 (COX‐2) expression in the paraventricular nucleus of hypothalamus (PVN), with synthesis of prostaglandin E2, contributes to augmented sympathetic nerve activity in heart failure (HF) rats. Increasing evidence has linked the expression of COX‐2 to activation of intracellular mitogen‐activated protein kinase (MAPK) pathways. We hypothesized that activation of central MAPK pathways mediates COX‐2 expression in the PVN in HF. Sprague‐Dawley rats underwent coronary ligation to induce HF or sham surgery (SHAM). HF rats were treated for 4 weeks with intracerebroventricular MAPK inhibitors or vehicle. Compared with SHAM, vehicle treated HF rats had increased (*p&lt;0.05) phosphorylated (normalized to total) p44/42 MAPK (0.22±0.02* vs 0.09±0.01; 0.24±0.02* vs 0.11±0.02), p38 MAPK (0.24±0.03* vs 0.12±0.02) and JNK (0.29±0.03* vs 0.15±0.02), increased COX‐2 mRNA (0.10±0.02* vs 0.04±0.01, normalized to GAPDH) in PVN, and increased PVN neuronal excitation (67±5* vs 25±4). A p38 MAPK inhibitor reduced COX‐2 mRNA in the PVN by 43% (p&lt;0.05, vs vehicle), but p44/42 MAPK and JNK inhibitors had no effect. All three inhibitors significantly decreased excitation of PVN neurons. These data indicate that p38 MAPK plays a critical role in HF‐induced COX‐2 expression in PVN, and so may contribute to augmented sympathetic nerve activity in HF. Supported by a VA Merit Review award.