Abstract
BACKGROUND: Paediatric High Grade Gliomas (HGG) have poor outcomes with conventional treatment. HGG in association with constitutional DNA mismatch repair deficiency (CMMRD) are hypermutated ...and have shown dramatic response to checkpoint inhibitors. Salvage following progression or failure to respond to check point inhibitors has rarely been reported. We describe a successful alternative therapeutic approach targeting the activated pathway (mTOR) in a hypermutated HGG. CASE SUMMARY: A 6-year-old girl presenting with seizures was diagnosed with left frontal lobe HGG with concurrent neck mass (Pilomatrixoma). Presence of synchronous tumours raised the possibility of cancer predisposition; the HGG was hypermutated with germline PMS2 mutation confirming diagnosis of CMMRD. Near total resection was undertaken followed by focal radiotherapy 54 Gy, with 1 cycle of concomitant CCNU. MRI post radiotherapy showed tumour progression. Anti-PDl inhibitor Nivolumab was commenced. CTLA-4 antibody, Ipilimumab was added after 4 cycles of Nivolumab due to poor response. Tumour response was seen, but dual therapy had to be discontinued due to toxicity. The tumour progressed following further single agent Nivolumab. In view of multiple mutations in the mTOR pathway (NF1, PIK3/PTEN, TSC1, TSC2), a mTOR inhibitor, Everolimus was commenced. There was 25% tumour reduction after 4 weeks treatment and further reduction after 6 months. Resection of residual tumour showed necrotic tissue only. There continues to be a sustained response to Everolimus for over 12 months. DISCUSSION: Approximately a third of CMMRD HGG respond to checkpoint inhibitors. For those that don’t, these hypermutated tumours offers the possibility of targeting specific molecular pathways. Response to Everolimus in HGG harbouring mTOR aberrations have been described. To our knowledge this is the first report of successful use of mTOR inhibitor in CMMRD HGG. CONCLUSION: Targeted molecular treatment for patients with CMMRD hypermutated brain tumours should be considered according to the mutated pathways.
Abstract
The survival of children with DIPG remains dismal, with new treatments desperately needed. In the era of precision medicine, targeted therapies represent an exciting treatment opportunity, ...yet resistance can rapidly emerge, playing an important role in treatment failure. In a prospective biopsy-stratified clinical trial (BIOMEDE), we combined detailed molecular profiling (methylation BeadArray, exome, RNAseq, phospho-proteomics) linked to drug screening in newly-established patient-derived models of DIPG in vitro and in vivo. We identified a high degree of in vitro sensitivity to the MEK inhibitor trametinib (GI50 16-50nM) in samples which harboured genetic alterations targeting the MAPK pathway, including the non-canonical BRAF_G469V mutation, and those affecting PIK3R1. Treatment of PDX models and the patient with trametinib at relapse, however, failed to elicit a significant response. We generated trametinib-resistant clones (62-188-fold, GI50 2.4–5.2µM) in the BRAF_G469V model through continuous drug exposure, and identified acquired mutations in MEK1/2 (MEK1_K57N, MEK1_I141S and MEK2_I115N) with sustained pathway up-regulation. These cells showed the hallmarks of mesenchymal transition, with overexpression of key proteins involved in invasion/migration, such as collagen-family proteins, integrins, MMPs and AHNAK2, amongst others. Resistant clones were conversely sensitive to the upstream receptor tyrosine kinase inhibitor dasatinib (GI50 36-93nM), and combinations of trametinib with dasatinib and the downstream ERK inhibitor ulixertinib showed synergistic effects in vitro. These data highlight the MAPK pathway as a therapeutic target in DIPG, and show the importance of parallel resistance modelling and rational combinatorial treatments likely to be required for meaningful clinical translation.
Abstract
INTRODUCTION
MAPK pathway activation is a druggable target and characteristic of paediatric low-grade(pLGG) and also found in high-grade glioma(pHGG), typically resulting from ...BRAFV600E/BRAF-fusion/NF1 mutations.
METHODS
A retrospective cohort study of 23 patients, who received BRAF inhibitor monotherapy (BRAFi)(11 BRAFV600E, one BRAFV600D mutation), MEKi monotherapy (MEKi) (6 BRAF fusion and 4 with NF1) or BRAFi and MEKi combination (Combi) therapy (2 BRAF V600 mutations).
RESULTS
12 patients were treated with BRAFi, with a median of 51.5 weeks treatment, (5 pHGG, 7 pLGG). 10 patients with pLGG were treated with MEKi (median of 30 weeks treatment). Toxicity of BRAFi included development of new melanocytic naevi (73%), erythema nodosum (60%), pyrexia (42%), xerosis (40%), hair changes (27%) and raised creatinine (17%). Toxicity of MEKi included acneform/papulopustular rash (65%), paronychia (59%), hair changes (57%), xerosis (47%) and mouth ulcers (20%). No patient stopped treatment due to toxicity. Response evaluations are available for 11 BRAFi patients, of whom 3 have PR (2 pLGG, 1pHGG), 2 have MR (pLGG), 3 have SD (pLGG) and 2 patients had PD (pHGG). 1 further patient with pHGG, had an initial prolonged SD (102 weeks on BRAFi), developed a new lesion, which subsequently responded to addition of MEKi therapy. Response evaluations are available for 9 MEKi patients (all with LGG) of whom 2 had PR, 4 had SD and 3 patients had PD. 1 patient with pLGG treated with Combi had MR.
CONCLUSION
Both BRAFi and MEKi therapy were well tolerated and provided significant and durable responses in paediatric glioma.
Abstract
The survival of children with diffuse intrinsic pontine glioma (DIPG) remains dismal, with new treatments desperately needed. In the era of precision medicine, targeted therapies represent ...an exciting treatment opportunity, yet resistance can rapidly emerge, playing an important role in treatment failure. In a prospective biopsy-stratified clinical trial, we combined detailed molecular profiling (methylation BeadArray, exome, RNAseq, phospho-proteomics) linked to drug screening in newly-established patient-derived models of DIPG in vitro and in vivo. We identified a high degree of in vitro sensitivity to the MEK inhibitor trametinib (GI50 16-50nM) in samples, which harboured genetic alterations targeting the MAPK pathway, including the non-canonical BRAF_G469V mutation, and those affecting PIK3R1 and NF1. However, treatment of PDX models and of a patient with trametinib at relapse failed to elicit a significant response. We generated trametinib-resistant clones (62-188-fold, GI50 2.4–5.2µM) in the BRAF_G469V model through continuous drug exposure, and identified acquired mutations in MEK1/2 (MEK1_K57N, MEK1_I141S and MEK2_I115N) with sustained pathway up-regulation. These cells showed the hallmarks of mesenchymal transition, and expression signatures overlapping with inherently trametinib-insensitive primary patient-derived cells that predicted an observed sensitivity to dasatinib. Combinations of trametinib with dasatinib and the downstream ERK inhibitor ulixertinib showed highly synergistic effects in vitro. These data highlight the MAPK pathway as a therapeutic target in DIPG, and show the importance of parallel resistance modelling and rational combinatorial treatments likely to be required for meaningful clinical translation.
The survival of children with diffuse intrinsic pontine glioma (DIPG) remains dismal, with new treatments desperately needed. In a prospective biopsy-stratified clinical trial, we combined detailed ...molecular profiling and drug screening in newly established patient-derived models in vitro and in vivo. We identified in vitro sensitivity to MEK inhibitors in DIPGs harboring MAPK pathway alterations, but treatment of patient-derived xenograft models and a patient at relapse failed to elicit a significant response. We generated trametinib-resistant clones in a BRAFG469V model through continuous drug exposure and identified acquired mutations in MEK1/2 with sustained pathway upregulation. These cells showed hallmarks of mesenchymal transition and expression signatures overlapping with inherently trametinib-insensitive patient-derived cells, predicting sensitivity to dasatinib. Combined trametinib and dasatinib showed highly synergistic effects in vitro and on ex vivo brain slices. We highlight the MAPK pathway as a therapeutic target in DIPG and show the importance of parallel resistance modeling and combinatorial treatments for meaningful clinical translation.
We report alterations in the MAPK pathway in DIPGs to confer initial sensitivity to targeted MEK inhibition. We further identify for the first time the mechanism of resistance to single-agent targeted therapy in these tumors and suggest a novel combinatorial treatment strategy to overcome it in the clinic. This article is highlighted in the In This Issue feature, p. 587.
Background
Kaposi sarcoma (KS) is the most common paediatric cancer in human immunodeficiency virus (HIV) endemic countries of sub‐Saharan Africa, but there is little research on management and ...outcomes.
Methods
Children with KS at Queen Elizabeth Central Hospital, Blantyre, Malawi treated between August 2012 and March 2015 with six courses of vincristine, bleomycin and etoposide combination chemotherapy, including antiretroviral therapy (ART) if HIV infected, were studied and outcomes compared with previously reported results.
Findings
Fifty‐six children were included; 38 (68%) were male; and 48 (86%) were HIV positive, of whom 36 (77%) were on ART at diagnosis. Median age at diagnosis was 8 years (interquartile range IQR 3–12) and median follow‐up was 16.9 months (IQR 3.4–36.4). Quality of life improved in 45 (80%) children; the median Lansky Score increased from 80% pre‐treatment to 100% post‐treatment. Eighteen (32%) children had complete response to treatment. At 12 months, overall survival was 71% (95% confidence interval CI 56–82) and event‐free survival (event = death, loss to follow‐up or relapse) was 50% (95% CI 36–63). At 1 year, the risk of loss to follow‐up was 13.4%. In a previous, same‐site, randomized controlled study of vincristine monotherapy, vincristine and bleomycin, or oral etoposide, oral etoposide monotherapy had the best outcome with survival at 12 month of 66% (95% CI 46–80) and event‐free survival of 52% (95% CI 33–68); however, loss to follow‐up was not reported.
Conclusion
Overall survival, event‐free survival and quality of life appear to have improved with this three‐agent combination chemotherapy; however larger, randomized studies are needed to determine optimal management.
Abstract Introduction Kaposi’s sarcoma (KS) is a common childhood cancer in places where HIV is endemic and access to antiretroviral therapy (ART) is delayed. Despite this there are no randomised ...trials to compare and assess chemotherapeutic regimens. Method An open label, randomised trial comparing intravenous vincristine alone, vincristine and bleomycin and oral etoposide, was carried out in children with Kaposi’s sarcoma in the Queen Elizabeth Central Hospital, Blantyre, Malawi. HIV infected children were given ART after 2–3 courses of chemotherapy if they were not already on treatment. Neither HIV nor widespread KS are curable and treatment is aimed at disease reduction and improved quality of life. Tumour reduction was assessed by measuring the size of sentinel KS nodules and quality of life (QoL) by using the Lansky score. Follow up was until death or for one year. Findings 92 children were enrolled of whom 46% were naïve to ART; 10 (11%) were HIV negative. Survival was not influenced by age or gender but was better in the oral etoposide and the vincristine and bleomycin groups. P = 0.0045. The group receiving oral etoposide had a better quality of life. Toxicity was not significant, and any drop in haemoglobin or white cell count could have been causally related to HIV infection rather than cytotoxic therapy. Conclusion Oral etoposide is a safe, effective treatment to contain KS and improve QoL which can be achieved without many visits to the hospital and intravenous injections.
Abstract
The survival of children with DIPG remains dismal, and new treatments are desperately needed. The development of patient-specific in vitro and in vivo models represents one such opportunity, ...however the time taken to establish such models and the rapid disease progression has been thought to limit the utility of such an approach. We sought to explore a co-clinical trial model for DIPG patients enrolled in an ongoing biopsy-stratified study in order to identify rational therapeutic options with individualised preclinical evidence as to their efficacy. To date we have established novel patient-derived in vitro cultures from biopsy specimens of 11 patients, in both 2D (laminin matrix) and 3D (neurosphere) conditions, as well as orthotopic xenografts in vivo, with a high concordance in their molecular profile compared to the original tumour specimen (methylation BeadArray, exome, RNA sequencing). Cells were screened against a series of common and bespoke FDA-approved drugs based upon previous evidence in DIPG and/or the specific molecular alterations found in the patient sample. We identified a high degree of in vitro sensitivity to the MEK inhibitor trametinib (GI50 23-312nM) in samples which harboured genetic alterations targeting the MAPK pathway, specifically the non-canonical BRAF_G469V mutation and those affecting PIK3R1(N564D, H450E_VF_ins), with assessment of tumour volume in vivo by MRI. Allelic imbalance of PIK3R1_N564D by stochastic selection was observed in two independent cultures from the same patient showing a greater response to trametinib (6.4-fold) as well as a decreased sensitivity to dasatinib in the mutant-enriched culture (38-fold). RNAseq of the cultures revealed differential gene expression associated with hypoxia and interferon signalling linked to drug sensitivity. These data show the feasibility in generating patient-specific, testable hypotheses that may be clinically translated in a subset of patients, and we are currently exploring parallel resistance modelling to further inform novel treatment strategies at tumour progression.
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