Sleep and pulmonary outcomes for clinical trials of airway plexiform neurofibromas in NF1

Polysomnographic study in pediatric neurofibromatosis type 1

Background

Neurofibromatosis type 1 (NF1) is a genetic disease that alters neurodevelopment. We aimed to analyze the sleep macrostructure of a sample of children affected by NF1 without neurocognitive co-morbidities and MRI reports of unidentified bright objects (UBOs).

Methods

A 100 pre-pubertal children participated in the cross-sectional study: 50 subjects were children diagnosed with NF1 and 50 subjects were typically developing healthy children (TDC). All participants underwent polysomnographic evaluation through which conventional sleep parameters were collected: Total sleep time (TST), Sleep latency (SOL), first REM latency (FRL), number of stage shifts/h (SS/h), number of awakenings/h (AWN/h), wake after sleep onset (WASO%), sleep efficiency percentage (SE%), percentage of sleep time spent in sleep stages 1 (N1%) and 2 (N2%), slow-wave sleep (N3%), and REM sleep (REM%). Additionally, nocturnal respiratory events such as apnea/hypopnea index (AHI), oxygen desaturation index (ODI), and periodic limb movement index (PLMI) were recorded.

Results

Neurofibromatosis type 1 children showed a reduction in sleep duration parameters (TST; p < 0.001), sleep efficiency (SE%; p < 0.001), and stage N2% (p < 0.001). Moreover, the number of awakenings per hour (AWN/h), wake after sleep onset (WASO%), and respiratory events such as AHI, ODI, and PLMI resulted higher in NF1 vs. TDC children.

Conclusion

The data showed that the sleep macrostructure differs between NF1 and TDC children. These findings suggest that the evaluation of sleep may provide useful support in corroborating the diagnosis and offers additional therapeutic management perspectives in NF1 and genetic neurodevelopmental disorders in general.

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.

Vinblastine/Methotrexate for Debilitating and Progressive Plexiform Neurofibroma in Children and Young Adults with Neurofibromatosis Type 1: A Phase 2 Study

Limited therapies exist for neurofibromatosis type 1 (NF1)-associated plexiform neurofibroma (PN). For this reason, the activity of vinblastine (VBL) and methotrexate (MTX) was evaluated in children and young adults with NF1 and PN. Patients ≤ 25 years of age with progressive and/or inoperable NF1-PN received VBL 6 mg/m² and MTX 30 mg/m² weekly for 26 weeks, followed by every 2 weeks for 26 weeks. Objective response rate was the primary endpoint. Of 25 participants enrolled, 23 were evaluable. The median age of participants was 6.6 years (range 0.3-20.7). The most frequent toxicities were neutropenia and elevation of transaminases. On two-dimensional (2D) imaging, 20 participants (87%) had stable tumor, with a median time to progression of 41.5 months (95% confidence interval 16.9, 64.9). Two of eight participants (25%) with airway involvement demonstrated functional improvements including decreased positive pressure requirements and apnea-hypopnea index. A post hoc three-dimensional (3D) analysis of PN volumes was completed on 15 participants with amenable imaging; 7 participants (46%) had progressive disease on or by the end of therapy. VBL/MTX was well-tolerated but did not result in objective volumetric response. Furthermore, 3D volumetric analysis highlighted the lack of sensitivity of 2D imaging for PN response evaluation.

Management of neurofibromatosis type 1-associated plexiform neurofibromas

Plexiform Neurofibromas (PN) are a common manifestation of the genetic disorder neurofibromatosis type 1 (NF1). These benign nerve sheath tumors often cause significant morbidity, with treatment options limited historically to surgery. There have been tremendous advances over the past two decades in our understanding of PN, and the recent regulatory approvals of the MEK inhibitor selumetinib are reshaping the landscape for PN management. At present, there is no agreed upon PN definition, diagnostic evaluation, surveillance strategy, or clear indications for when to initiate treatment and selection of treatment modality. In this review, we address these questions via consensus recommendations from a panel of multidisciplinary NF1 experts.

Sleep-disordered breathing in pediatric neurofibromatosis type 1

The relationship between neurofibromatosis type 1 (NF1) and sleep-disordered breathing (SDB) has not been widely studied. The aim of the study was to analyze SDB in children with NF1 of the respiratory system. All children with NF1 followed between September 2008 and July 2020 who had a respiratory polygraphy (RP) were included. The clinical charts, cerebral and cervical magnetic resonance imaging (MRI), and RP were analyzed. Twenty-two patients (11 girls, median age at RP 8.3 [0.2-18.2] years) were included in the study. Nine patients (41%) had a NF1 involvement of the upper airways, 13 (59%) patients of the central nervous system (CNS), the cranial nerves (CN) and/or medulla, and 17 (77%) patients had a hypertrophy of the adenoids and/or tonsils. Five patients were treated with Continuous positive airway pressure (CPAP) or noninvasive ventilation (NIV) before their first evaluation because of severe obstructive sleep apnea (OSA). Accordingly, 10 (45%) patients had no OSA, one (5%) mild OSA, 2 (9%) moderate OSA, and nine (41%) severe OSA. None of the patients had central sleep apnea. Despite upper airway surgery, three patients required CPAP, two could be weaned and one died after a switch to tracheostomy. None of the patients treated with CPAP/NIV could be weaned, one patient required tracheostomy. Neither the clinical nor the MRI findings were able to predict OSA on a RP. The prevalence of OSA in NF1 is high, regardless of the nature of airway obstruction and the clinical and MRI findings, underlining the value of a systematic RP. CPAP may reduce the need of tracheostomy.

OUP accepted manuscript

BACKGROUND

Selumetinib was recently approved for the treatment of inoperable symptomatic plexiform neurofibromas (PNs) in children with neurofibromatosis type 1 (NF1). This parallel phase II study determined the response rate to selumetinib in children with NF1 PN without clinically significant morbidity.

METHODS

Children with NF1 and inoperable PNs, which were not yet causing clinically significant morbidity but had the potential to cause symptoms, received selumetinib at 25 mg/m2 orally twice daily (1 cycle = 28 days). Volumetric magnetic resonance imaging analysis and outcome assessments, including patient-reported (PRO), observer-reported, and functional outcome measures were performed every 4 cycles for 2 years, with changes assessed over time. A confirmed partial response (cPR) was defined as PN volume decrease of ≥20% on at least 2 consecutive scans ≥3 months apart.

RESULTS

72% of subjects experienced a cPR on selumetinib. Participants received selumetinib for a median of 41 cycles (min 2, max 67) at data cutoff. Approximately half of the children rated having some target tumor pain at baseline, which significantly decreased by pre-cycle 13. Most objectively measured baseline functions, including visual, motor, bowel/bladder, or airway function were within normal limits and did not clinically or statistically worsen during treatment.

CONCLUSIONS

Selumetinib resulted in PN shrinkage in most subjects with NF1 PN without clinically significant morbidity. No new PN-related symptoms developed while on selumetinib, and PRO measures indicated declines in tumor-related pain intensity. This supports that selumetinib treatment may prevent the development of PN-related morbidities, though future prospective studies are needed to confirm these results.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT01362803.

A Systematic Review and Meta-Analysis of Enzyme Replacement Therapy in Late-Onset Pompe Disease

Pompe disease (PD) is a glycogen storage disorder caused by deficient activity of acid alpha-glucosidase (GAA). We sought to review the latest available evidence on the safety and efficacy of recombinant human GAA enzyme replacement therapy (ERT) for late-onset PD (LOPD).

METHODS

We systematically searched the MEDLINE (via PubMed), Embase, and Cochrane databases for prospective clinical studies evaluating ERT for LOPD on pre-specified outcomes. A meta-analysis was also performed.

RESULTS

Of 1601 articles identified, 22 were included. Studies were heterogeneous and with very low certainty of evidence for most outcomes. The following outcomes showed improvements associated with GAA ERT, over a mean follow-up of 32.5 months: distance walked in the 6-min walking test (6MWT) (mean change 35.7 m (95% confidence interval [CI] 7.78, 63.75)), physical domain of the SF-36 quality of life (QOL) questionnaire (mean change 1.96 (95% CI 0.33, 3.59)), and time on ventilation (TOV) (mean change -2.64 h (95% CI -5.28, 0.00)). There were no differences between the pre- and post-ERT period for functional vital capacity (FVC), Walton and Gardner-Medwin Scale score, upper-limb strength, or total SF-36 QOL score. Adverse events (AEs) after ERT were mild in most cases.

CONCLUSION

Considering the limitations imposed by the rarity of PD, our data suggest that GAA ERT improves 6MWT, physical QOL, and TOV in LOPD patients. ERT was safe in the studied population. PROSPERO register: 135102.

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.

Reliability of Handheld Dynamometry to Measure Focal Muscle Weakness in Neurofibromatosis Types 1 and 2

OBJECTIVE

To determine a suitable outcome measure for assessing muscle strength in neurofibromatosis (NF) type 1 and NF2 clinical trials, we evaluated the intraobserver reliability of handheld dynamometry (HHD) and developed consensus recommendations for its use in NF clinical trials.

METHODS

Patients ≥5 years of age with weakness in at least 1 muscle group by manual muscle testing (MMT) were eligible. Maximal isometric muscle strength of a weak muscle group and the biceps of the dominant arm was measured by HHD. An average of 3 repetitions per session was used as an observation, and 3 sessions with rest period between each were performed on the same day by a single observer. Intrasession and intersession intraclass correlation coefficients (ICCs) and coefficients of variation (CVs) were calculated to assess reliability and measurement error.

RESULTS

Twenty patients with NF1 and 13 with NF2 were enrolled; median age was 12 years (interquartile range [IQR] 9-17 years) and 29 years (IQR 22-38 years), respectively. By MMT, weak muscle strength ranged from 2-/5 to 4+/5. Biceps strength was 5/5 in all patients. Intersession ICCs for the weak muscles were 0.98 and 0.99 in the NF1 and NF2 cohorts, respectively, and for biceps were 0.97 and 0.97, respectively. The median CVs for average session strength were 5.4% (IQR 2.6%-7.3%) and 2.9% (IQR 2.0%-6.2%) for weak muscles and biceps, respectively.

CONCLUSION

HHD performed by a trained examiner with a well-defined protocol is a reliable technique to measure muscle strength in NF1 and NF2. Recommendations for strength testing in NF1 and NF2 trials are provided.

Clinical trial design in neurofibromatosis type 1 as a model for other tumor predisposition syndromes

Up to 10% of all pediatric cancer patients may have an underlying germline mutation which predisposed them to develop a malignancy. With more patients being tested for and diagnosed with genetic tumor predisposition syndromes, there has been improved characterization of their many nonmalignant manifestations. However, designing and implementing clinical trials to treat the nonmalignant tumor and non-tumor manifestations of these syndromes poses many unique challenges. Unlike trials for malignancies where tumor response and survival can be used as straightforward trial endpoints, the nonmalignant manifestations are often chronic, evolve more slowly over time, and may not be immediately life-threatening. Therefore, they will likely require a different approach to both testing and treatment with a focus on more functional and patient-reported outcome trial endpoints. The recent success of treatment trials for the benign tumors plexiform neurofibromas in the tumor predisposition syndrome neurofibromatosis type 1 (NF1) can be used as a model for the development of clinical trials in other tumor predisposition syndromes. In this article, we review the unique challenges associated with targeting the nonmalignant aspects of these conditions as well as some of the lessons learned from the NF1 experience which may be applied to other syndromes in the future.

Selumetinib in Children with Inoperable Plexiform Neurofibromas

BACKGROUND

No approved therapies exist for inoperable plexiform neurofibromas in patients with neurofibromatosis type 1.

METHODS

We conducted an open-label, phase 2 trial of selumetinib to determine the objective response rate among patients with plexiform neurofibromas and to assess clinical benefit. Children with neurofibromatosis type 1 and symptomatic inoperable plexiform neurofibromas received oral selumetinib twice daily at a dose of 25 mg per square meter of body-surface area on a continuous dosing schedule (28-day cycles). Volumetric magnetic resonance imaging and clinical outcome assessments (pain, quality of life, disfigurement, and function) were performed at least every four cycles. Children rated tumor pain intensity on a scale from 0 (no pain) to 10 (worst pain imaginable).

RESULTS

A total of 50 children (median age, 10.2 years; range, 3.5 to 17.4) were enrolled from August 2015 through August 2016. The most frequent neurofibroma-related symptoms were disfigurement (44 patients), motor dysfunction (33), and pain (26). A total of 35 patients (70%) had a confirmed partial response as of March 29, 2019, and 28 of these patients had a durable response (lasting ≥1 year). After 1 year of treatment, the mean decrease in child-reported tumor pain-intensity scores was 2 points, considered a clinically meaningful improvement. In addition, clinically meaningful improvements were seen in child-reported and parent-reported interference of pain in daily functioning (38% and 50%, respectively) and overall health-related quality of life (48% and 58%, respectively) as well as in functional outcomes of strength (56% of patients) and range of motion (38% of patients). Five patients discontinued treatment because of toxic effects possibly related to selumetinib, and 6 patients had disease progression. The most frequent toxic effects were nausea, vomiting, or diarrhea; an asymptomatic increase in the creatine phosphokinase level; acneiform rash; and paronychia.

CONCLUSIONS

In this phase 2 trial, most children with neurofibromatosis type 1 and inoperable plexiform neurofibromas had durable tumor shrinkage and clinical benefit from selumetinib. (Funded by the Intramural Research Program of the National Institutes of Health and others; ClinicalTrials.gov number, NCT01362803.).

After Nf1 loss in Schwann cells, inflammation drives neurofibroma formation

Plexiform neurofibromas (PNF) are peripheral nerve tumors caused by bi-allelic loss of NF1 in the Schwann cell (SC) lineage. PNF are common in individuals with Neurofibromatosis type I (NF1) and can cause significant patient morbidity, spurring research into potential therapies. Immune cells are rare in peripheral nerve, whereas in PNF 30% of the cells are monocytes/macrophages. Mast cells, T cells, and dendritic cells (DCs) are also present. NF1 mutant neurofibroma SCs with elevated Ras-GTP signaling resemble injury-induced repair SCs, in producing growth factors and cytokines not normally present in SCs. This provides a cytokine-rich environment facilitating PNF immune cell recruitment and fibrosis. We propose a model based on genetic and pharmacologic evidence in which, after loss of Nf1 in the SC lineage, a lag occurs. Then, mast cells and macrophages are recruited to nerve. Later, T cell/DC recruitment through CXCL10/CXCR3 drives neurofibroma initiation and sustains PNF macrophages and tumor growth. Stat3 signaling is an additional critical mediator of neurofibroma initiation, cytokine production, and PNF growth. At each stage of PNF development therapeutic benefit should be achievable through pharmacologic modulation of leukocyte recruitment and function.