FDA Approval Summary: Selumetinib for Plexiform Neurofibroma

Contemporary Approach to Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors

Most malignant peripheral nerve sheath tumors (MPNSTs) are clinically aggressive high-grade sarcomas, arising in individuals with neurofibromatosis type 1 (NF1) at a significantly elevated estimated lifetime frequency of 8%-13%. In the setting of NF1, MPNSTs arise from malignant transformation of benign plexiform neurofibroma and borderline atypical neurofibromas. Composed of neoplastic cells from the Schwannian lineage, these cancers recur in approximately 50% of individuals, and most patients die within five years of diagnosis, despite surgical resection, radiation, and chemotherapy. Treatment for metastatic disease is limited to cytotoxic chemotherapy and investigational clinical trials. In this article, we review the pathophysiology of this aggressive cancer and current approaches to surveillance and treatment.

Development and pilot validation of a novel disfigurement severity scale for plexiform neurofibromas in children with neurofibromatosis type 1

BACKGROUND/AIMS

We developed an observer disfigurement severity scale for neurofibroma-related plexiform neurofibromas to assess change in plexiform neurofibroma-related disfigurement and evaluated its feasibility, reliability, and validity.

METHODS

Twenty-eight raters, divided into four cohorts based on neurofibromatosis type 1 familiarity and clinical experience, were shown photographs of children in a clinical trial (NCT01362803) at baseline and 1 year on selumetinib treatment for plexiform neurofibromas (n = 20) and of untreated participants with plexiform neurofibromas (n = 4). Raters, blinded to treatment and timepoint, completed the 0-10 disfigurement severity score for plexiform neurofibroma on each image (0 = not at all disfigured, 10 = very disfigured). Raters evaluated the ease of completing the scale, and a subset repeated the procedure to assess intra-rater reliability.

RESULTS

Mean baseline disfigurement severity score for plexiform neurofibroma ratings were similar for the selumetinib group (6.23) and controls (6.38). Mean paired differences between pre- and on-treatment ratings was -1.01 (less disfigurement) in the selumetinib group and 0.09 in the control (p = 0.005). For the disfigurement severity score for plexiform neurofibroma ratings, there was moderate-to-substantial agreement within rater cohorts (weighted kappa range = 0.46-0.66) and agreement between scores of the same raters at repeat sessions (p > 0.05). In the selumetinib group, change in disfigurement severity score for plexiform neurofibroma ratings was moderately correlated with change in plexiform neurofibroma volume with treatment (r = 0.60).

CONCLUSION

This study demonstrates that our observer-rated disfigurement severity score for plexiform neurofibroma was feasible, reliable, and documented improvement in disfigurement in participants with plexiform neurofibroma shrinkage. Prospective studies in larger samples are needed to validate this scale further.

MEK Inhibition for RASopathy-Associated Hypertrophic Cardiomyopathy: Clinical Application of a Basic Concept

The term "RASopathies" designates a group of developmental syndromes that are caused by activating variants of the rat sarcoma virus protein (RAS)/mitogen-activated protein kinase (MAPK) cascade. The most prevalent clinical diagnosis is Noonan syndrome, and other, less prevalent conditions include Noonan syndrome with multiple lentigines, Costello syndrome, cardiofaciocutaneous syndrome, and others. Hypertrophic cardiomyopathy occurs in 10% of these patients and can be severe and life-threating. Recently, repurposing of medications inhibiting the RAS/MAPK on a compassionate use basis has emerged as a promising concept to improve the outcome of these patients. Herein, we specifically review the role of the RAS/MAPK pathway in RASopathy-associated cardiomyopathy, and discuss the role of small-molecule inhibition in the treatment of this condition. We describe how drug repurposing of trametinib (mitogen-activated protein/extracellular signal-regulated kinase inhibition) and sirolimus/everolimus (mammalian target of rapamycin inhibition) was performed, how genotype-specific therapies are chosen and followed, as well as initial outcomes from early case series. Finally, we lay out the challenges and opportunities for trials that aim to quantify the benefits of this approach.

Novel therapeutic perspectives in Noonan syndrome and RASopathies

Noonan syndrome belongs to the family of RASopathies, a group of multiple congenital anomaly disorders caused by pathogenic variants in genes encoding components or regulators of the RAS/mitogen-activated protein kinase (MAPK) signalling pathway. Collectively, all these pathogenic variants lead to increased RAS/MAPK activation. The better understanding of the molecular mechanisms underlying the different manifestations of NS and RASopathies has led to the identification of molecular targets for specific pharmacological interventions. Many specific agents (e.g. SHP2 and MEK inhibitors) have already been developed for the treatment of RAS/MAPK-driven malignancies. In addition, other molecules with the property of modulating RAS/MAPK activation are indicated in non-malignant diseases (e.g. C-type natriuretic peptide analogues in achondroplasia or statins in hypercholesterolemia).  Conclusion: Drug repositioning of these molecules represents a challenging approach to treat or prevent medical complications associated with RASopathies. What is Known: • Noonan syndrome and related disorders are caused by pathogenic variants in genes encoding components or regulators of the RAS/mitogen-activated protein kinase (MAPK) signalling pathway, resulting in increased activation of this pathway. • This group of disorders is now known as RASopathies and represents one of the largest groups of multiple congenital anomaly diseases known. What is New: • The identification of pathophysiological mechanisms provides new insights into the development of specific therapeutic strategies, in particular treatment aimed at reducing RAS/MAPK hyperactivation. • Drug repositioning of specific agents already developed for the treatment of malignant (e.g. SHP2 and MEK inhibitors) or non-malignant diseases (e.g. C-type natriuretic peptide analogues in achondroplasia or statins in hypercholesterolaemia) represents a challenging approach to the treatment of RASopathies.

The NF1+/- Immune Microenvironment: Dueling Roles in Neurofibroma Development and Malignant Transformation

Neurofibromatosis type 1 (NF1) is a common genetic disorder resulting in the development of both benign and malignant tumors of the peripheral nervous system. NF1 is caused by germline pathogenic variants or deletions of the NF1 tumor suppressor gene, which encodes the protein neurofibromin that functions as negative regulator of p21 RAS. Loss of NF1 heterozygosity in Schwann cells (SCs), the cells of origin for these nerve sheath-derived tumors, leads to the formation of plexiform neurofibromas (PNF)-benign yet complex neoplasms involving multiple nerve fascicles and comprised of a myriad of infiltrating stromal and immune cells. PNF development and progression are shaped by dynamic interactions between SCs and immune cells, including mast cells, macrophages, and T cells. In this review, we explore the current state of the field and critical knowledge gaps regarding the role of NF1(Nf1) haploinsufficiency on immune cell function, as well as the putative impact of Schwann cell lineage states on immune cell recruitment and function within the tumor field. Furthermore, we review emerging evidence suggesting a dueling role of Nf1+/- immune cells along the neurofibroma to MPNST continuum, on one hand propitiating PNF initiation, while on the other, potentially impeding the malignant transformation of plexiform and atypical neurofibroma precursor lesions. Finally, we underscore the potential implications of these discoveries and advocate for further research directed at illuminating the contributions of various immune cells subsets in discrete stages of tumor initiation, progression, and malignant transformation to facilitate the discovery and translation of innovative diagnostic and therapeutic approaches to transform risk-adapted care.

Neurofibromatosis type 1: Clinical characteristics and mutation spectrum in a North Indian cohort

Background

Neurofibromatosis type 1 (NF1) is a unique, highly penetrant neuro-cutaneous disorder with a wide range of manifestations. Though the clinical diagnosis of NF1 is straight forward, there can be other disorders which mimic NF1, especially its cutaneous features. Here we describe the clinical and mutation spectrum of a series of individuals whose primary diagnosis was NF1 or NF1 related disorders.

Methods

We have screened 29 unrelated individuals who fulfilled the clinical criteria of NF1. Whole exome sequencing (WES) was done in all individuals except one with suspected microdeletion syndrome with NF1 in whom Cytogenetic microarray (CMA) was done.

Results

Out of 29 suspected patients, 25 had germline pathogenic/likely pathogenic variants involving NF1 gene. Five novel and 20 known variants in coding and non-coding regions were identified, among them 7 variants were deletions (28%), 7 nonsense (28%), 3 splice-site (12%), 4 missense (16%), 2 duplications (8%) and 2 (8%) were contiguous deletions. In those where NF1 variants were not detected, 3 had neurofibromatosis type 2 (NF2) and 1 rare autosomal recessive form of Elher Danlos syndrome.

Conclusion

We hereby present the wide range of manifestations in different age groups and the mutation spectrum ranging from small scale variants to contiguous gene deletion syndromes involving NF1 gene. We highlight the usefulness of molecular testing and its importance in tumor surveillance and genetic counseling in this disorder.

Targeting the RAS/RAF/MAPK pathway for cancer therapy: from mechanism to clinical studies

Metastatic dissemination of solid tumors, a leading cause of cancer-related mortality, underscores the urgent need for enhanced insights into the molecular and cellular mechanisms underlying metastasis, chemoresistance, and the mechanistic backgrounds of individuals whose cancers are prone to migration. The most prevalent signaling cascade governed by multi-kinase inhibitors is the mitogen-activated protein kinase (MAPK) pathway, encompassing the RAS-RAF-MAPK kinase (MEK)-extracellular signal-related kinase (ERK) pathway. RAF kinase is a primary mediator of the MAPK pathway, responsible for the sequential activation of downstream targets, such as MEK and the transcription factor ERK, which control numerous cellular and physiological processes, including organism development, cell cycle control, cell proliferation and differentiation, cell survival, and death. Defects in this signaling cascade are associated with diseases such as cancer. RAF inhibitors (RAFi) combined with MEK blockers represent an FDA-approved therapeutic strategy for numerous RAF-mutant cancers, including melanoma, non-small cell lung carcinoma, and thyroid cancer. However, the development of therapy resistance by cancer cells remains an important barrier. Autophagy, an intracellular lysosome-dependent catabolic recycling process, plays a critical role in the development of RAFi resistance in cancer. Thus, targeting RAF and autophagy could be novel treatment strategies for RAF-mutant cancers. In this review, we delve deeper into the mechanistic insights surrounding RAF kinase signaling in tumorigenesis and RAFi-resistance. Furthermore, we explore and discuss the ongoing development of next-generation RAF inhibitors with enhanced therapeutic profiles. Additionally, this review sheds light on the functional interplay between RAF-targeted therapies and autophagy in cancer.

Development of a MEK inhibitor, NFX-179, as a chemoprevention agent for squamous cell carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer. Although cSCC contributes to substantial morbidity and mortality in high-risk individuals, deployment of otherwise effective chemoprevention of cSCC is limited by toxicities. Our systematic computational drug repurposing screen predicted that selumetinib, a MAPK (mitogen-activated protein kinase) kinase inhibitor (MEKi), would reverse transcriptional signatures associated with cSCC development, consistent with our genomic analysis implicating MEK as a chemoprevention target. Although systemic MEKi suppresses the formation of cSCC in mice, systemic MEKi can cause severe adverse effects. Here, we report the development of a metabolically labile MEKi, NFX-179, designed to potently and selectively suppress the MAPK pathway in the skin before rapid metabolism in the systemic circulation. NFX-179 was identified on the basis of its biochemical and cellular potency, selectivity, and rapid metabolism upon systemic absorption. In our ultraviolet-induced cSCC mouse model, topical application of NFX-179 gel reduced the formation of new cSCCs by an average of 60% at doses of 0.1% and greater at 28 days. We further confirmed the localized nature of these effects in an additional split-mouse randomized controlled study where suppression of cSCC was observed only in drug-treated areas. No toxicities were observed. NFX-179 inhibits the growth of human SCC cell lines in a dose-dependent manner, and topical NFX-179 application penetrates human skin and inhibits MAPK signaling in human cSCC explants. Together, our data provide a compelling rationale for using topical MEK inhibition through the application of NFX-179 gel as an effective strategy for cSCC chemoprevention.

Shedding New Light: Novel Therapies for Common Disorders in Children with Neurofibromatosis Type I

Neurofibromatosis type I (NF1) is a common dominantly inherited disorder, and one of the most common of the RASopathies. Most individuals with NF1 develop plexiform neurofibromas and cutaneous neurofibromas, nerve tumors caused by NF1 loss of function in Schwann cells. Cell culture models and mouse models of NF1 are being used to test drug efficacy in preclinical trials, which led to Food and Drug Administration approval for use of MEK inhibitors to shrink most inoperable plexiform neurofibromas. This article details methods used for testing in preclinical models, and outlines newer models that may identify additional, curative, strategies.

Endoglin, a Novel Biomarker and Therapeutical Target to Prevent Malignant Peripheral Nerve Sheath Tumor Growth and Metastasis

PURPOSE

Malignant peripheral nerve sheath tumors (MPNST) are highly aggressive soft-tissue sarcomas that lack effective treatments, underscoring the urgent need to uncover novel mediators of MPNST pathogenesis that may serve as potential therapeutic targets. Tumor angiogenesis is considered a critical event in MPNST transformation and progression. Here, we have investigated whether endoglin (ENG), a TGFβ coreceptor with a crucial role in angiogenesis, could be a novel therapeutic target in MPNSTs.

EXPERIMENTAL DESIGN

ENG expression was evaluated in human peripheral nerve sheath tumor tissues and plasma samples. Effects of tumor cell-specific ENG expression on gene expression, signaling pathway activation and in vivo MPNST growth and metastasis, were investigated. The efficacy of ENG targeting in monotherapy or in combination with MEK inhibition was analyzed in xenograft models.

RESULTS

ENG expression was found to be upregulated in both human MPNST tumor tissues and plasma-circulating small extracellular vesicles. We demonstrated that ENG modulates Smad1/5 and MAPK/ERK pathway activation and pro-angiogenic and pro-metastatic gene expression in MPNST cells and plays an active role in tumor growth and metastasis in vivo. Targeting with ENG-neutralizing antibodies (TRC105/M1043) decreased MPNST growth and metastasis in xenograft models by reducing tumor cell proliferation and angiogenesis. Moreover, combination of anti-ENG therapy with MEK inhibition effectively reduced tumor cell growth and angiogenesis.

CONCLUSIONS

Our data unveil a tumor-promoting function of ENG in MPNSTs and support the use of this protein as a novel biomarker and a promising therapeutic target for this disease.

Combination of Genomic Landsscape and 3D Culture Functional Assays Bridges Sarcoma Phenotype to Target and Immunotherapy

Genomic-based precision medicine has not only improved tumour therapy but has also shown its weaknesses. Genomic profiling and mutation analysis have identified alterations that play a major role in sarcoma pathogenesis and evolution. However, they have not been sufficient in predicting tumour vulnerability and advancing treatment. The relative rarity of sarcomas and the genetic heterogeneity between subtypes also stand in the way of gaining statistically significant results from clinical trials. Personalized three-dimensional tumour models that reflect the specific histologic subtype are emerging as functional assays to test anticancer drugs, complementing genomic screening. Here, we provide an overview of current target therapy for sarcomas and discuss functional assays based on 3D models that, by recapitulating the molecular pathways and tumour microenvironment, may predict patient response to treatments. This approach opens new avenues to improve precision medicine when genomic and pathway alterations are not sufficient to guide the choice of the most promising treatment. Furthermore, we discuss the aspects of the 3D culture assays that need to be improved, such as the standardisation of growth conditions and the definition of in vitro responses that can be used as a cut-off for clinical implementation.

The Contribution of Oxidative Stress to NF1-Altered Tumors

The neurofibromatosis-1 gene (NF1) was initially characterized because its germline mutation is responsible for an inherited syndromic disease predisposing tumor development, in particular neurofibromas but also various malignancies. Recently, large-scale tumor sequencing efforts have demonstrated NF1 as one of the most frequently mutated genes in human cancer, being mutated in approximately 5-10% of all tumors, especially in malignant peripheral nerve sheath tumors and different skin tumors. NF1 acts as a tumor suppressor gene that encodes neurofibromin, a large protein that controls neoplastic transformation through several molecular mechanisms. On the other hand, neurofibromin loss due to NF1 biallelic inactivation induces tumorigenic hyperactivation of Ras and mTOR signaling pathways. Moreover, neurofibromin controls actin cytoskeleton structure and the metaphase-anaphase transition. Consequently, neurofibromin deficiency favors cell mobility and proliferation as well as chromosomal instability and aneuploidy, respectively. Growing evidence supports the role of oxidative stress in NF1-related tumorigenesis. Neurofibromin loss induces oxidative stress both directly and through Ras and mTOR signaling activation. Notably, innovative therapeutic approaches explore drug combinations that further increase reactive oxygen species to boost the oxidative unbalance of NF1-altered cancer cells. In our paper, we review NF1-related tumors and their pathogenesis, highlighting the twofold contribution of oxidative stress, both tumorigenic and therapeutic.

Consensus-Based Best Practice Guidelines for the Management of Spinal Deformity and Associated Tumors in Pediatric Neurofibromatosis Type 1: Screening and Surveillance, Surgical Intervention, and Medical Therapy

BACKGROUND

Spinal conditions, such as scoliosis and spinal tumors, are prevalent in neurofibromatosis type 1 (NF1). Despite the recognized importance of their early detection and treatment, there remain knowledge gaps in how to approach these manifestations. The purpose of this study was to utilize the experience of a multidisciplinary committee of experts to establish consensus-based best practice guidelines (BPGs) for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric patients with NF1.

METHODS

Using the results of a prior systematic review, 10 key questions that required further assessment were first identified. A committee of 20 experts across medical specialties was then chosen based on their clinical experience with spinal deformity and tumors in NF1. These were 9 orthopaedic surgeons, 4 neuro-oncologists/oncologists, 3 neurosurgeons, 2 neurologists, 1 pulmonologist, and 1 clinical geneticist. An initial online survey on current practices and opinions was conducted, followed by 2 additional surveys via a formal consensus-based modified Delphi method. The final survey involved voting on agreement or disagreement with 35 recommendations. Items reaching consensus (≥70% agreement or disagreement) were included in the final BPGs.

RESULTS

Consensus was reached for 30 total recommendations on the management of spinal deformity and tumors in NF1. These were 11 recommendations on screening and surveillance, 16 on surgical intervention, and 3 on medical therapy. Five recommendations did not achieve consensus and were excluded from the BPGs.

CONCLUSION

We present a set of consensus-based BPGs comprised of 30 recommendations for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric NF1.

Treatment decisions and the use of MEK inhibitors for children with neurofibromatosis type 1-related plexiform neurofibromas

Neurofibromatosis type 1 (NF1), the most common tumor predisposition syndrome, occurs when NF1 gene variants result in loss of neurofibromin, a negative regulator of RAS activity. Plexiform neurofibromas (PN) are peripheral nerve sheath tumors that develop in patients with NF1 and are associated with substantial morbidity and for which, until recently, the only treatment was surgical resection. However, surgery carries several risks and a proportion of PN are considered inoperable. Understanding the genetic underpinnings of PN led to the investigation of targeted therapies as medical treatment options, and the MEK1/2 inhibitor selumetinib has shown promising efficacy in pediatric patients with NF1 and symptomatic, inoperable PN. In a phase I/II trial, most children (approximately 70%) achieved reduction in tumor volume accompanied by improvements in patient-reported outcomes (decreased tumor-related pain and improvements in quality of life, strength, and range of motion). Selumetinib is currently the only licensed medical therapy indicated for use in pediatric patients with symptomatic, inoperable NF1-PN, with approval based on the results of this pivotal clinical study. Several other MEK inhibitors (binimetinib, mirdametinib, trametinib) and the tyrosine kinase inhibitor cabozantinib are also being investigated as medical therapies for NF1-PN. Careful consideration of multiple aspects of both disease and treatments is vital to reduce morbidity and improve outcomes in patients with this complex and heterogeneous disease, and clinicians should be fully aware of the risks and benefits of available treatments. There is no single treatment pathway for patients with NF1-PN; surgery, watchful waiting, and/or medical treatment are options. Treatment should be individualized based on recommendations from a multidisciplinary team, considering the size and location of PN, effects on adjacent tissues, and patient and family preferences. This review outlines the treatment strategies currently available for patients with NF1-PN and the evidence supporting the use of MEK inhibitors, and discusses key considerations in clinical decision-making.

Advancements in therapeutic approaches for malignant peripheral nerve sheath tumor

Tweetable abstract Emerging targeted therapies offer hope for malignant peripheral nerve sheath tumor. Innovative drug delivery enhances potential treatments. #MPNST #TargetedTherapies #TherapeuticDelivery.

The genetic landscape and possible therapeutics of neurofibromatosis type 2

Neurofibromatosis type 2 (NF2) is a genetic condition marked by the development of multiple benign tumors in the nervous system. The most common tumors associated with NF2 are bilateral vestibular schwannoma, meningioma, and ependymoma. The clinical manifestations of NF2 depend on the site of involvement. Vestibular schwannoma can present with hearing loss, dizziness, and tinnitus, while spinal tumor leads to debilitating pain, muscle weakness, or paresthesias. Clinical diagnosis of NF2 is based on the Manchester criteria, which have been updated in the last decade. NF2 is caused by loss-of-function mutations in the NF2 gene on chromosome 22, leading the merlin protein to malfunction. Over half of NF2 patients have de novo mutations, and half of this group are mosaic. NF2 can be managed by surgery, stereotactic radiosurgery, monoclonal antibody bevacizumab, and close observation. However, the nature of multiple tumors and the necessity of multiple surgeries over the lifetime, inoperable tumors like meningiomatosis with infiltration of the sinus or in the area of the lower cranial nerves, the complications caused by the operation, the malignancies induced by radiotherapy, and inefficiency of cytotoxic chemotherapy due to the benign nature of NF-related tumors have led a march toward exploring targeted therapies. Recent advances in genetics and molecular biology have allowed identifying and targeting of underlying pathways in the pathogenesis of NF2. In this review, we explain the clinicopathological characteristics of NF2, its genetic and molecular background, and the current knowledge and challenges of implementing genetics to develop efficient therapies.

Dermatologic Manifestations of Neurofibromatosis Type 1 and Emerging Treatments

Neurofibromatosis type 1 (NF1) is an autosomal dominant tumor predisposition syndrome that increases one's risk for both benign and malignant tumors. NF1 affects every organ in the body, but the most distinctive symptoms that are often the most bothersome to patients are the cutaneous manifestations, which can be unsightly, cause pain or pruritus, and have limited therapeutic options. In an effort to increase awareness of lesser-known dermatologic associations and to promote multidisciplinary care, we conducted a narrative review to shed light on dermatologic associations of NF1 as well as emerging treatment options. Topics covered include cutaneous neurofibromas, plexiform neurofibromas, diffuse neurofibromas, distinct nodular lesions, malignant peripheral nerve sheath tumors, glomus tumors, juvenile xanthogranulomas, skin cancer, and cutaneous T-cell lymphoma.

Bioinformatics and cheminformatics approaches to identify pathways, molecular mechanisms and drug substances related to genetic basis of cervical cancer

Cervical cancer (CC) is a global threat to women and our knowledge is frighteningly little about its underlying genomic contributors. Our research aimed to understand the underlying molecular and genetic mechanisms of CC by integrating bioinformatics and network-based study. Transcriptomic analyses of three microarray datasets identified 218 common differentially expressed genes (DEGs) within control samples and CC specimens. KEGG pathway analysis revealed pathways in cell cycle, drug metabolism, DNA replication and the significant GO terms were cornification, proteolysis, cell division and DNA replication. Protein-protein interaction (PPI) network analysis identified 20 hub genes and survival analyses validated CDC45, MCM2, PCNA and TOP2A as CC biomarkers. Subsequently, 10 transcriptional factors (TFs) and 10 post-transcriptional regulators were detected through TFs-DEGs and miRNAs-DEGs regulatory network assessment. Finally, the CC biomarkers were subjected to a drug-gene relationship analysis to find the best target inhibitors. Standard cheminformatics method including in silico ADMET and molecular docking study substantiated PD0325901 and Selumetinib as the most potent candidate-drug for CC treatment. Overall, this meticulous study holds promises for further in vitro and in vivo research on CC diagnosis, prognosis and therapies. Communicated by Ramaswamy H. Sarma.

FDA regulatory considerations for the review of drugs intended to treat pediatric cancers and rare tumors

PURPOSE OF REVIEW

We describe select recent FDA approvals in pediatric cancers and rare tumors, and the unique regulatory considerations raised by each application.

RECENT FINDINGS

The approvals of naxitamab, selumetinib, selpercatinib, and crizotinib for pediatric and adolescent patients between April 2020 and January 2021 all represented first FDA approvals in their respective pediatric or adolescent populations. In addition, all represent approvals of targeted therapies administered in select patient populations, and were based on overall response rate (ORR) and duration of response (DOR) data in single-arm trials.

SUMMARY

Recent approvals for the pediatric oncology indications have often, but not always, relied in part upon investigator-sponsored clinical trials. Early engagement with regulatory agencies to discuss drug development in rare populations is critical to obtain early agreement on trial design and streamline development. Although reliance on ORR and DOR data may be feasible to support an approval, the ability to rely on response rate depends on many factors, including the disease context, reliability of radiographic assessment, and the results of the trial. In some cases, a time-to-event endpoint may be most appropriate to assess clinical benefit; early consideration should be given to the feasibility of conducting of a randomized trial.

Transcriptional Antagonism by CDK8 Inhibition Improves Therapeutic Efficacy of MEK Inhibitors

Aberrant RAS/MAPK signaling is a common driver of oncogenesis that can be therapeutically targeted with clinically approved MEK inhibitors. Disease progression on single-agent MEK inhibitors is common, however, and combination therapies are typically required to achieve significant clinical benefit in advanced cancers. Here we focused on identifying MEK inhibitor-based combination therapies in neuroblastoma with mutations that activate the RAS/MAPK signaling pathway, which are rare at diagnosis but frequent in relapsed neuroblastoma. A genome-scale CRISPR-Cas9 functional genomic screen was deployed to identify genes that when knocked out sensitize RAS-mutant neuroblastoma to MEK inhibition. Loss of either CCNC or CDK8, two members of the mediator kinase module, sensitized neuroblastoma to MEK inhibition. Furthermore, small-molecule kinase inhibitors of CDK8 improved response to MEK inhibitors in vitro and in vivo in RAS-mutant neuroblastoma and other adult solid tumors. Transcriptional profiling revealed that loss of CDK8 or CCNC antagonized the transcriptional signature induced by MEK inhibition. When combined, loss of CDK8 or CCNC prevented the compensatory upregulation of progrowth gene expression induced by MEK inhibition. These findings propose a new therapeutic combination for RAS-mutant neuroblastoma and may have clinical relevance for other RAS-driven malignancies.

SIGNIFICANCE

Transcriptional adaptation to MEK inhibition is mediated by CDK8 and can be blocked by the addition of CDK8 inhibitors to improve response to MEK inhibitors in RAS-mutant neuroblastoma, a clinically challenging disease.

The next generation of evidence-based medicine

Recently, advances in wearable technologies, data science and machine learning have begun to transform evidence-based medicine, offering a tantalizing glimpse into a future of next-generation 'deep' medicine. Despite stunning advances in basic science and technology, clinical translations in major areas of medicine are lagging. While the COVID-19 pandemic exposed inherent systemic limitations of the clinical trial landscape, it also spurred some positive changes, including new trial designs and a shift toward a more patient-centric and intuitive evidence-generation system. In this Perspective, I share my heuristic vision of the future of clinical trials and evidence-based medicine.

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

As the mitogen-activated protein kinase (MAPK) signalling pathway is activated in many paediatric cancers, it is an important therapeutic target. Currently, a range of targeted MAPK pathway inhibitors are being developed in adults. However, MAPK signals through many cascades and feedback loops and perturbing the MAPK pathway may have substantial influence on other pathways as well as normal development. In view of these issues, the ninth Paediatric Strategy Forum focused on MAPK inhibitors. Development of MAPK pathway inhibitors to date has been predominantly driven by adult indications such as malignant melanoma. However, these inhibitors may also target unmet needs in paediatric low-grade gliomas, high-grade gliomas, Langerhans cell histiocytosis, juvenile myelomonocytic leukaemia and several other paediatric conditions. Although MAPK inhibitors have demonstrated activity in paediatric cancer, the response rates and duration of responses needs improvement and better documentation. The rapid development and evaluation of combination approaches, based on a deep understanding of biology, is required to optimise responses and to avoid paradoxical tumour growth and other unintended consequences including severe toxicity. Better inhibitors with higher central nervous systempenetration for primary brain tumours and cancers with a propensity for central nervous system metastases need to be studied to determine if they are more effective than agents currently being used, and the optimum duration of therapy with MAPK inhibition needs to be determined. Systematic and coordinated clinical investigations to inform future treatment strategies with MAPK inhibitors, rather than use outside of clinical trials, are needed to fully assess the risks and benefits of these single agents and combination strategies in both front-line and in the refractory/relapse settings. Platform trials could address the investigation of multiple similar products and combinations. Accelerating the introduction of MAPK inhibitors into front-line paediatric studies is a priority, as is ensuring that these studies generate data appropriate for scientific and regulatory purposes. Early discussions with regulators are crucial, particularly if external controls are considered as randomised control trials in small patient populations can be challenging. Functional end-points specific to the populations in which they are studied, such as visual acuity, motor and neuro psychological function are important, as these outcomes are often more reflective of benefit for lower grade tumours (such as paediatric low-grade glioma and plexiform neurofibroma) and should be included in initial study designs for paediatric low-grade glioma. Early prospective discussions and agreements with regulators are necessary. Long-term follow-up of patients receiving MAPK inhibitors is crucial in view of their prolonged administration and the important involvement of this pathway in normal development. Further rational development, with a detailed understanding of biology of this class of products, is crucial to ensure they provide optimal benefit while minimising toxicity to children and adolescents with cancer.

New prospectives on treatment opportunities in RASopathies

The RASopathies are a group of clinically defined developmental syndromes caused by germline variants of the RAS/mitogen-activated protein (MAPK) cascade. The prototypic RASopathy is Noonan syndrome, which has phenotypic overlap with related disorders such as cardiofaciocutaneous syndrome, Costello syndrome, Noonan syndrome with multiple lentigines, and others. In this state-of-the-art review, we summarize current knowledge on unmet therapeutic needs in these diseases and novel treatment approaches informed by insights from RAS/MAPK-associated cancer therapies, in particular through inhibition of MEK1/2 and mTOR in patients with severe disease manifestations. We explore the possibilities of integrating a larger arsenal of molecules currently under development into future care plans. Lastly, we describe both medical and ethical challenges and opportunities for future clinical trials in the field.

Identification of the Major Degradation Pathways of Selumetinib

Selumetinib is administered orally in capsule form and is indicated for the treatment of neurofibromatosis. To facilitate dosage adjustments, liquid preparations, such as solutions or suspensions, are to be developed. This led, first, to determine the stability profile of soluble or dispersed selumetinib and, secondly, to look for ways to stabilize the active substance. The degradation kinetics of selumetinib as a function of stress conditions were determined and compared. The degradation products were detected and identified by LC-HRMSⁿ. In solution, selumetinib is sensitive to oxidation and degrades by photooxidation. In both cases, the side chain represented by the oxoamide group is concerned, leading to the formation of an amide derivative for the first case and an ester derivative for the second. The identification of such degradation mechanisms allowed us to study, in a targeted way, processes aiming at stabilizing the active molecule.

A Systematic Review of Recent and Ongoing Clinical Trials in Patients With the Neurofibromatoses

INTRODUCTION

The neurofibromatoses comprise three different genetic conditions causing considerable morbidity and mortality: neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis (SWN). This review summarizes recent and ongoing clinical trials involving patients with neurofibromatoses to better understand the current state of clinical trial research centered around these conditions and inform areas of need.

METHODS

A search was conducted using the Cochrane Central Register of Controlled Trials and clinicaltrials.gov databases. Inclusion and exclusion criteria were designed to identify clinical trials focused on patients with NF1, NF2, or SWN completed in or after 2010 and in process as of December 31, 2021. Information was collected using standardized guidelines.

RESULTS

A total of 134 clinical trials were included, with 75 (56%) completed and 59 (44%) in process. For completed trials, 74% (n = 56) involved patients with NF1, and of those based on specific tumors (n = 26, 46%), the majority focused on plexiform neurofibromas (PNs) (n = 12, 46%). For ongoing trials, 79% (n = 47) involve patients with NF1, and of those based on specific tumors (n = 29, 61%), the majority are focused on PNs (n = 13, 45%).

CONCLUSION

Both recent and ongoing clinical trials have primarily focused on patients with NF1 and the treatment of PNs. This research has led to the first FDA-approved drug for NF1-PN and has changed management of these tumors, allowing for systemic therapy rather than reliance on only a surgical modality. Trials evaluating comorbid psychiatric conditions and quality of life among patients with any of the neurofibromatoses appear less common. These areas may warrant focus in future studies to improve clinical management.

The protein kinase CK1: Inhibition, activation, and possible allosteric modulation

Protein kinases play a vital role in biology and deregulation of kinases is implicated in numerous diseases ranging from cancer to neurodegenerative diseases, making them a major target class for the pharmaceutical industry. However, the high degree of conservation that exists between ATP-binding sites among kinases makes it difficult for current inhibitors to be highly specific. In the context of neurodegeneration, several groups including ours, have linked different kinases such as CK1 and Alzheimer’s disease for example. Strictly CK1-isoform specific regulators do not exist and known CK1 inhibitors are inhibiting the enzymatic activity, targeting the ATP-binding site. Here we review compounds known to target CK1, as well as other inhibitory types that could benefit CK1. We introduce the DNA-encoded library (DEL) technology that might represent an interesting approach to uncover allosteric modulators instead of ATP competitors. Such a strategy, taking into account known allosteric inhibitors and mechanisms, might help designing modulators that are more specific towards a specific kinase, and in the case of CK1, toward specific isoforms.

Mechanistic insights from animal models of neurofibromatosis type 1 cognitive impairment

Neurofibromatosis type 1 (NF1) is an autosomal-dominant neurogenetic disorder caused by mutations in the gene neurofibromin 1 (NF1). NF1 predisposes individuals to a variety of symptoms, including peripheral nerve tumors, brain tumors and cognitive dysfunction. Cognitive deficits can negatively impact patient quality of life, especially the social and academic development of children. The neurofibromin protein influences neural circuits via diverse cellular signaling pathways, including through RAS, cAMP and dopamine signaling. Although animal models have been useful in identifying cellular and molecular mechanisms that regulate NF1-dependent behaviors, translating these discoveries into effective treatments has proven difficult. Clinical trials measuring cognitive outcomes in patients with NF1 have mainly targeted RAS signaling but, unfortunately, resulted in limited success. In this Review, we provide an overview of the structure and function of neurofibromin, and evaluate several cellular and molecular mechanisms underlying neurofibromin-dependent cognitive function, which have recently been delineated in animal models. A better understanding of neurofibromin roles in the development and function of the nervous system will be crucial for identifying new therapeutic targets for the various cognitive domains affected by NF1.

Summary: Neurofibromin influences neural circuits through RAS, cAMP and dopamine signaling. Exploring the mechanisms underlying neurofibromin-dependent behaviors in animal models might enable future treatment of the various cognitive deficits that are associated with neurofibromatosis type 1.

Epidemiological profile and clinical characteristics of 491 Brazilian patients with neurofibromatosis type 1

BACKGROUND

Neurofibromatosis type 1 (NF1) is a chronic and progressive autosomal dominant genetic and sporadic disease characterized by cutaneous and neurological abnormalities. Plexiform neurofibroma (PN), a significant cause of clinical complications in NF-1, is a benign tumor of the peripheral nerve sheath that involves multiple nerve fascicles. Although there is an important number of patients who are affected by NF1 in Brazil, there is little data on the behavior of the disease in the national literature as well as in other low- and middle-income countries.

METHODS

We performed a retrospective analysis of 491 patients with NF1 followed at two reference centers in Brazil.

RESULTS

Approximately 38% of patients had PNs, resulting in reduced life quality. The median patient age with PNs was 30 years (range: 6 to 83 years). Head and neck, and extremity were the main affected locations with 35.8 and 30.6%, respectively. PNs were classified as asymptomatic in 25.1% of patients, while 52.5% presented symptomatic and inoperable tumors. The most common manifestations related to PNs were disfigurement and orthopedic involvement. Twenty patients developed neoplasms and ten (50%) presented with malignant peripheral nerve sheath tumors (MPNST). The prevalence of MPNST in our study was 2.9%.

CONCLUSIONS

Patients with NF1 experience clinically significant morbidity, especially when it is associated with PN. Though there are many patients affected by NF1 in Brazil and other low- and middle-income countries, there is little data available in the corresponding literature. Our results are comparable to the previous results reported from higher-income countries and international registries.

Clinical Trials Targeting Neurofibromatoses-associated Tumors: A Systematic Review

Background

There is a paucity of literature that comprehensively analyzes previous and current clinical trials targeting neurofibromatoses-related tumors. This article aims to provide readers with drug development efforts targeting these tumors by analyzing translational and clinical findings.

Methods

This systematic review was written according to the PRISMA guidelines. Inclusion criteria were clinical trials involving patients with neurofibromatosis type 1, type 2, or schwannomatosis that were treated with therapies targeting neurofibromatoses-associated tumors and that were registered on clinicaltrials.gov. In addition, a search was performed in PubMed, Web of Science, Google Scholar, and Embase European for articles fully describing these clinical trials.

Results

A total of 265 clinical trials were registered and screened for eligibility. Ninety-two were included in this systematic review involving approximately 4636 participants. The number of therapies analyzed was more than 50. Drugs under investigation mainly act on the MAPK/ERK and PI3K/AKT/mTOR pathways, tumor microenvironment, or aberrantly over-expressed cell surface receptors. Selumetinib was the most effective medication for treating a neurofibromatosis type 1-associated tumor with approximately 68%–71% partial response for inoperable or progressive plexiform neurofibromas in children 2 years of age and older and bevacizumab for a neurofibromatosis type 2-related tumor with approximately 36%–41% partial response for vestibular schwannomas in patients 12 years of age and older.

Conclusions

This systematic review presents the results of previous clinical investigations and those under development for neurofibromatoses-associated tumors. Clinicians may use this information to strategize patients to appropriate clinical trials.

Plexiform neurofibroma: shedding light on the investigational agents in clinical trials

INTRODUCTION

Neurofibromatosis Type 1 (NF1) is an autosomal dominant genetic condition, which predisposes individuals to the development of plexiform neurofibromas (PN), benign nerve sheath tumors seen in 30-50% of patients with NF1. These tumors may cause significant pain and disfigurement or may compromise organ function. Given the morbidity associated with these tumors, therapeutic options for patients with NF1-related PN are necessary.

AREAS COVERED

We searched the www.clinicaltrials.gov database for 'plexiform neurofibroma.' This article summarizes completed and ongoing trials involving systemic therapies for PN.

EXPERT OPINION

Surgery is the mainstay treatment; however, complete resection is not possible in many cases. Numerous systemic therapies have been evaluated in patients with NF1, with MEK inhibitors (MEKi) showing the greatest efficacy for volumetric reduction and improvement in functional and patient-reported outcomes. The MEKi selumetinib is now FDA approved for the treatment of inoperable, symptomatic PN in pediatric NF1 patients. Questions remain regarding the use of this drug class in terms of when to initiate therapy, overall duration, reduced dosing schedules, and side effect management. Future studies are needed to fully understand the clinical application of MEKi and to evaluate other potential therapies through appropriate trial designs for this potentially devastating, manifestation in NF1.

A Review of Selumetinib in the Treatment of Neurofibromatosis Type 1-Related Plexiform Neurofibromas

OBJECTIVE

To evaluate the safety and efficacy of selumetinib, a novel MEK inhibitor, for the treatment of plexiform neurofibromas (PN) in patients with neurofibromatosis type 1 (NF1).

DATA SOURCES

An English-based literature search of PubMed, EMBASE, and ClinicalTrials.gov was conducted using the terms selumetinib AND neurofibromatosis from inception to August 1, 2021.

STUDY SELECTION AND DATA EXTRACTION

Relevant prescribing information, abstracts, and articles identified through the search were considered for inclusion in this review.

DATA SYNTHESIS

The open-label, multicenter, single-arm, phase II SPRINT trial demonstrated clinically significant improvements in PN-related complications. Of 50 symptomatic patients, 68% experienced a partial response, with a median change in tumor volume of -27.9% from baseline. Estimated progression-free survival at 3 years was 84%. Additionally, clinically meaningful improvements were seen on patient- and parent-reported assessments evaluating pain, range of motion, disfigurement, and quality of life. Overall, the adverse effect profile for selumetinib appears mild and manageable.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Selumetinib is the first FDA-approved treatment for inoperable PN in patients with NF1, demonstrating that MEK inhibition is a promising therapeutic strategy. Studies are ongoing to assess the effect of selumetinib on other NF1-associated tumor types and to determine the optimal dosing schedule and treatment duration. Cost and treatment burden must be considered when selecting selumetinib therapy.

CONCLUSION

Selumetinib exhibits impressive antitumor activity and sustained clinical benefit in patients lacking other viable treatment options. Further studies are warranted to determine the optimal age of initiation, treatment duration, and overall cost-effectiveness of selumetinib.

Integrative pan-cancer analysis of MEK1 aberrations and the potential clinical implications

Alterations of mitogen-activated protein kinase kinase 1 (MEK1) are commonly associated with tumorigenesis, and MEK1 is thought to be a suitable targeted therapy for various cancers. However, abnormal MEK1 alterations and their relevant clinical implications are unknown. Our research comprehensively analyzed the MEK1 alteration spectrum and provided novel insight for targeted therapies. There were 7694 samples covering 32 types of cancer from The Cancer Genome Atlas (TCGA) database. They were used to conduct an integrative analysis of MEK1 expression, alterations, functional impacts and clinical significance. There was a dramatic difference in the alteration frequency and distribution and clinical implications in 32 types of cancer from the TCGA. Skin cutaneous melanoma (SKCM) has the most alterations and has therapeutic targets located in the protein kinase domain, and the growing expression of SKCM is positively related to patient prognosis. MEK1 expression in lung adenocarcinoma (LUAD), kidney renal papillary cell carcinoma (KIRP), esophageal carcinoma (ESCA) and liver hepatocellular carcinoma (LIHC) is decreased, which is associated with better prognosis, while MEK1 expression in thymoma (THYM), stomach adenocarcinoma (STAD), kidney renal clear cell carcinoma (KIRC), testicular germ cell tumors (TGCTs) and head and neck squamous cell carcinoma (HNSC) is increased, which is associated with better prognosis. Mesothelioma (MESO) has the second highest alterations but has no therapy targets. This study provided a great and detailed interpretation of MEK1 expression, alterations and clinical implications in 32 types of cancer and reminded us to fill the gap in MEK1 research from a new perspective.