pyrimidinones and Neurofibromatosis-1

Topics: Glomus Tumor; Humans; Neurofibromatosis 1; Pain; Pyridones; Pyrimidinones

NCI-MATCH is a precision medicine trial using genomic testing to allocate patients with advanced malignancies to targeted treatment subprotocols. This report combines two subprotocols evaluating trametinib, a MEK1/2 inhibitor, in patients with. Eligible patients had tumors with deleterious inactivating. Fifty patients were eligible and started therapy: 46 with. Although these subprotocols did not meet the primary end point for ORR, significant responses or prolonged SD noted in some disease subtypes warrants further investigation.

Topics: GTP-Binding Protein alpha Subunits; GTP-Binding Protein alpha Subunits, Gq-G11; Humans; Melanoma; Neurofibromatosis 1; Pyridones; Pyrimidinones

Plexiform neurofibromas (PNF) in neurofibromatosis type 1 (NF1) are usually diagnosed in childhood and can grow rapidly during this period. In 10% of patients, PNF involve the orbital-periorbital area and may cause visual problems including glaucoma, visual loss from amblyopia (deprivational, strabismic, or refractive), optic nerve compression, or keratopathy. Ptosis, proptosis, and facial disfigurement lead to social problems and decreased self-esteem. Complete surgical removal involves significant risks and mutilation, and regrowth after debulking is not uncommon. Inhibitors of the RAS/MAPK pathway have recently been investigated for their activity in PNF. We administered the oral MEK inhibitor trametinib to five young children with NF1 and PNF of the orbital area, with visual compromise and progressive tumor growth; and followed them clinically and by volumetric MRI.. Treatment was initiated at a mean age of 26.8 months (SD ± 12.8) and continued for a median 28 months (range 16-51). Doses were 0.025 mg/kg/day for children aged > 6 years and 0.032 mg/kg/day for those aged < 6 years.. Volumetric MRI measurements showed a reduction of 2.9-33% at 1 year after treatment initiation, with maximal reductions of 44% and 49% in two patients, at 44 and 36 months, respectively. No change in visual function was recorded during treatment. One child reported decreased orbital pain after 2 weeks; and another, with involvement of the masseters, had increased ability to chew food. Toxicities were mostly to skin and nails, grades 1-2.. Trametinib can decrease tumor size in some young children with orbital PNF and may prevent progressive disfigurement.

Topics: Child; Child, Preschool; Humans; Neurofibroma, Plexiform; Neurofibromatosis 1; Pyridones; Pyrimidinones

To describe a series of children with extensive PNF or treatment refractory PLGG treated on a compassionate basis with trametinib.. We report on six patients with NF-1 treated with trametinib on a compassionate basis at British Columbia Children's Hospital since 2017. Data were collected retrospectively from the patient record. RAPNO and volumetric criteria were used to evaluate the response of intracranial and extracranial lesions, respectively.. Subjects were 21 months to 14 years old at the time of initiation of trametinib therapy and 3/6 subjects are male. Duration of therapy was 4-28 months at the time of this report. All patients had partial response or were stable on analysis. Two patients with life-threatening PNF had a partial radiographic response in tandem with significant clinical improvement and developmental catch up. One subject discontinued therapy after 6 months due to paronychia and inadequate response. The most common adverse effect (AE) was grade 1-2 paronychia or dermatitis in 5/6 patients. There were no grade 3 or 4 AEs. At the time of this report, five patients remain on therapy.. Trametinib is an effective therapy for advanced PNF and refractory PLGG in patients with NF-1 and is well tolerated in children. Further data and clinical trials are required to assess tolerance, efficacy and durability of response, and length of treatment required in such patients.

Topics: Adolescent; Antineoplastic Agents; Brain Neoplasms; British Columbia; Child; Child, Preschool; Compassionate Use Trials; Dermatitis, Atopic; Drug Resistance, Neoplasm; Female; Glioma; Humans; Infant; Male; Neurofibroma, Plexiform; Neurofibromatosis 1; Paronychia; Pyridones; Pyrimidinones; Retrospective Studies; Treatment Outcome

Topics: Administration, Oral; Antifungal Agents; Biopsy; Drug Eruptions; Fluconazole; Folliculitis; Follow-Up Studies; Humans; Malassezia; Neurofibroma, Plexiform; Neurofibromatosis 1; Pyridones; Pyrimidinones; Retrospective Studies; Skin; Treatment Outcome

Topics: Antineoplastic Agents; Astrocytoma; Drug Resistance, Neoplasm; Humans; Infant; Male; Neurofibromatosis 1; Prognosis; Pyridones; Pyrimidinones; Remission Induction; Salvage Therapy

Plexiform neurofibromas are congenital peripheral nerve sheath tumors characteristic of neurofibromatosis type 1 (NF1)-a frequent neurocutaneous disorder caused by mutations of the NF1 tumor suppressor gene. Since plexiform neurofibromas are a major cause of the burden of disease and may also progress to malignancy, many efforts have been undertaken to find a cure for these tumors. However, neither surgery nor medication has so far produced a breakthrough therapeutic success. Recently, a clinical phase I study reported significant shrinkage of plexiform neurofibromas following treatment with the MEK inhibitor selumetinib. Here, we report an 11-year-old NF1 patient with a large plexiform neurofibroma of the neck that had led to a sharp-angled kinking of the cervical spine and subsequent myelopathy. Although surgical stabilization of the cervical vertebral column was urgently recommended, the vertebral column was inaccessible due to extensive tumor growth. In this situation, treatment with the MEK inhibitor trametinib was initiated which resulted in a 22% reduction in tumor volume after 6 months of therapy and finally enabled surgery. These data show that MEK inhibitors may not lead to complete disappearance of NF1-associated plexiform neurofibromas but can be an essential step in a multimodal therapeutic approach for these tumors. The course of our patient suggests that MEK inhibitors are likely to play a significant role in providing a cure for one of the most devastating manifestations of NF1.

Topics: Antineoplastic Agents; Cervical Cord; Child; Female; Humans; Neurofibroma, Plexiform; Neurofibromatosis 1; Neurofibromin 1; Protein Kinase Inhibitors; Pyridones; Pyrimidinones; Treatment Outcome

Approximately 200 BRAF mutant alleles have been identified in human tumours. Activating BRAF mutants cause feedback inhibition of GTP-bound RAS, are RAS-independent and signal either as active monomers (class 1) or constitutively active dimers (class 2). Here we characterize a third class of BRAF mutants-those that have impaired kinase activity or are kinase-dead. These mutants are sensitive to ERK-mediated feedback and their activation of signalling is RAS-dependent. The mutants bind more tightly than wild-type BRAF to RAS-GTP, and their binding to and activation of wild-type CRAF is enhanced, leading to increased ERK signalling. The model suggests that dysregulation of signalling by these mutants in tumours requires coexistent mechanisms for maintaining RAS activation despite ERK-dependent feedback. Consistent with this hypothesis, melanomas with these class 3 BRAF mutations also harbour RAS mutations or NF1 deletions. By contrast, in lung and colorectal cancers with class 3 BRAF mutants, RAS is typically activated by receptor tyrosine kinase signalling. These tumours are sensitive to the inhibition of RAS activation by inhibitors of receptor tyrosine kinases. We have thus defined three distinct functional classes of BRAF mutants in human tumours. The mutants activate ERK signalling by different mechanisms that dictate their sensitivity to therapeutic inhibitors of the pathway.

Topics: Animals; Cell Line, Tumor; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Female; Humans; Indoles; MAP Kinase Signaling System; Melanoma; Mice; Mitogen-Activated Protein Kinase Kinases; Mutation; Neurofibromatosis 1; NIH 3T3 Cells; Oncogene Protein p21(ras); Protein Multimerization; Proto-Oncogene Proteins B-raf; Pyridones; Pyrimidinones; Sulfonamides; Vemurafenib; Xenograft Model Antitumor Assays

Neurofibromatosis type I (NF1) is an autosomal dominant disease with an incidence of 1/3000, caused by mutations in the NF1 gene, which encodes the RAS/GTPase-activating protein neurofibromin. Non-bone union after fracture (pseudarthrosis) in children with NF1 remains a challenging orthopedic condition to treat. Recent progress in understanding the biology of neurofibromin suggested that NF1 pseudarthrosis stems primarily from defects in the bone mesenchymal lineage and hypersensitivity of hematopoietic cells to TGFβ. However, clinically relevant pharmacological approaches to augment bone union in these patients remain limited. In this study, we report the generation of a novel conditional mutant mouse line used to model NF1 pseudoarthrosis, in which Nf1 can be ablated in an inducible fashion in osteoprogenitors of postnatal mice, thus circumventing the dwarfism associated with previous mouse models where Nf1 is ablated in embryonic mesenchymal cell lineages. An ex vivo-based cell culture approach based on the use of Nf1(flox/flox) bone marrow stromal cells showed that loss of Nf1 impairs osteoprogenitor cell differentiation in a cell-autonomous manner, independent of developmental growth plate-derived or paracrine/hormonal influences. In addition, in vitro gene expression and differentiation assays indicated that chronic ERK activation in Nf1-deficient osteoprogenitors blunts the pro-osteogenic property of BMP2, based on the observation that only combination treatment with BMP2 and MEK inhibition promoted the differentiation of Nf1-deficient osteoprogenitors. The in vivo preclinical relevance of these findings was confirmed by the improved bone healing and callus strength observed in Nf1osx (-/-) mice receiving Trametinib (a MEK inhibitor) and BMP2 released locally at the fracture site via a novel nanoparticle and polyglycidol-based delivery method. Collectively, these results provide novel evidence for a cell-autonomous role of neurofibromin in osteoprogenitor cells and insights about a novel targeted approach for the treatment of NF1 pseudoarthrosis.

Topics: Animals; Bone Morphogenetic Protein 2; Bone Regeneration; Cell Differentiation; Disease Models, Animal; Drug Delivery Systems; Humans; MAP Kinase Kinase Kinases; Mesenchymal Stem Cells; Mice; Mice, Knockout; Nanoparticles; Neurofibromatosis 1; Neurofibromin 1; Protein Kinase Inhibitors; Pseudarthrosis; Pyridones; Pyrimidinones