Menin inhibitors in pediatric acute leukemia: a comprehensive review and recommendations to accelerate progress in collaboration with adult leukemia and the international community.

Aberrant expression of HOX and MEIS1 family genes, as seen in KMT2A-rearranged, NUP98-rearranged, or NPM1-mutated leukemias leads to arrested differentiation and leukemia development. HOX family genes are essential gatekeepers of physiologic hematopoiesis, and their expression is regulated by the interaction between KMT2A and menin. Menin inhibitors block this interaction, downregulate the abnormal expression of MEIS1 and other transcription factors and thereby release the differentiation block. Menin inhibitors show significant clinical efficacy against KMT2A-rearranged and NPM1-mutated acute leukemias, with promising potential to address unmet needs in various pediatric leukemia subtypes. In this collaborative initiative, pediatric and adult hematologists/oncologists, and stem cell transplant physicians have united their expertise to explore the potential of menin inhibitors in pediatric leukemia treatment internationally. Our efforts aim to provide a comprehensive clinical overview of menin inhibitors, integrating preclinical evidence and insights from ongoing global clinical trials. Additionally, we propose future international, inclusive, and efficient clinical trial designs, integrating pediatric populations in adult trials, to ensure broad access to this promising therapy for all children and adolescents with menin-dependent leukemias.

Mezigdomide is effective alone and in combination with menin inhibition in preclinical models of KMT2A-r and NPM1c AML.

ABSTRACT: Small molecules that target the menin-KMT2A protein-protein interaction (menin inhibitors) have recently entered clinical trials in lysine methyltransferase 2A (KMT2A or MLL1)-rearranged (KMT2A-r) and nucleophosmin-mutant (NPM1c) acute myeloid leukemia (AML) and are demonstrating encouraging results. However, rationally chosen combination therapy is needed to improve responses and prevent resistance. We have previously identified IKZF1/IKAROS as a target in KMT2A-r AML and shown in preclinical models that IKAROS protein degradation with lenalidomide or iberdomide has modest single-agent activity yet can synergize with menin inhibitors. Recently, the novel IKAROS degrader mezigdomide was developed with greatly enhanced IKAROS protein degradation. In this study, we show that mezigdomide has increased preclinical activity in vitro as a single-agent in KMT2A-r and NPM1c AML cell lines, including sensitivity in cell lines resistant to lenalidomide and iberdomide. Further, we demonstrate that mezigdomide has the greatest capacity to synergize with and induce apoptosis in combination with menin inhibitors, including in MEN1 mutant models. We show that the superior activity of mezigdomide compared with lenalidomide or iberdomide is due to its increased depth, rate, and duration of IKAROS protein degradation. Single-agent mezigdomide was efficacious in 5 patient-derived xenograft models of KMT2A-r and 1 NPM1c AML. The combination of mezigdomide with the menin inhibitor VTP-50469 increased survival and prevented and overcame MEN1 mutations that mediate resistance in patients receiving menin inhibitor monotherapy. These results support prioritization of mezigdomide for early phase clinical trials in KMT2A-r and NPM1c AML, either as a single agent or in combination with menin inhibitors.

IKAROS and MENIN coordinate therapeutically actionable leukemogenic gene expression in MLL-r acute myeloid leukemia.

Acute myeloid leukemia (AML) remains difficult to treat and requires new therapeutic approaches. Potent inhibitors of the chromatin-associated protein MENIN have recently entered human clinical trials, opening new therapeutic opportunities for some genetic subtypes of this disease. Using genome-scale functional genetic screens, we identified IKAROS (encoded by IKZF1) as an essential transcription factor in KMT2A (MLL1)-rearranged (MLL-r) AML that maintains leukemogenic gene expression while also repressing pathways for tumor suppression, immune regulation and cellular differentiation. Furthermore, IKAROS displays an unexpected functional cooperativity and extensive chromatin co-occupancy with mixed lineage leukemia (MLL)1-MENIN and the regulator MEIS1 and an extensive hematopoietic transcriptional complex involving homeobox (HOX)A10, MEIS1 and IKAROS. This dependency could be therapeutically exploited by inducing IKAROS protein degradation with immunomodulatory imide drugs (IMiDs). Finally, we demonstrate that combined IKAROS degradation and MENIN inhibition effectively disrupts leukemogenic transcriptional networks, resulting in synergistic killing of leukemia cells and providing a paradigm for improved drug targeting of transcription and an opportunity for rapid clinical translation.

Menin Inhibitors in Acute Myeloid Leukemia-What Does the Future Hold?

ABSTRACT: Menin inhibitors constitute a novel class of agents targeting the underlying biology of nucleophosmin (NPM1) mutant and KMT2A (formerly known as MLL1) rearranged (KMT2Ar) acute leukemias. KMT2Ar acute leukemias constitute 5% to 10% of acute leukemias, and NPM1 mutations are identified in 30% of newly diagnosed acute myeloid leukemias (AMLs). In preclinical AML models, small molecule inhibitors of the menin-KMT2A protein-protein interaction induce differentiation, downregulate critical gene expression programs, and confer a survival advantage in patient-derived xenograft models of NPM1 mutant and KMT2Ar AML. Multiple clinical trials evaluating oral menin inhibitors in acute leukemias are ongoing. Preliminary results in relapsed/refractory NPM1 mutant and KMT2Ar AML have shown on-target effects, tolerable toxicity, and promising clinical activity. This review details the current clinical experience of menin inhibitors in AML and discusses how these agents can be successfully integrated into future therapeutic approaches.

Juvenile Granulosa Cell Tumor as the Presenting Feature of McCune-Albright Syndrome.

INTRODUCTION: GNAS mutations have been reported in both McCune-Albright syndrome (MAS) and juvenile granulosa cell tumors (JGCT) but have never been reported simultaneously in the same patient. CASE PRESENTATION: A 15-year-old girl developed secondary oligomenorrhea. Laboratory studies revealed suppressed gonadotropin levels with markedly elevated estradiol and inhibin B levels. Pelvic ultrasound showed a 12-cm heterogeneous right adnexal mass; pelvic magnetic resonance imaging to further characterize the mass displayed heterogeneous bilateral femoral bone lesions initially concerning for metastatic disease. Positron emission tomography/computed tomography showed minimal 18F-fluorodeoxyglucose (FDG) uptake in the pelvic mass but unexpectedly revealed FDG uptake throughout the skeleton, concerning for polyostotic fibrous dysplasia in the context of MAS. The adnexal mass was excised and pathology confirmed a JGCT. The patient's affected bone and JGCT tissue revealed the same pathogenic GNAS p.R201C mutation, while her peripheral blood contained wild-type arginine at codon 201. CONCLUSION: This mutation has been previously reported in cases of MAS and JGCT but never simultaneously in the same patient. This demonstration of a GNAS mutation underlying both JGCT and MAS in the same patient raises questions about appropriate surveillance for patients with these conditions.

Financial impact of post-transplant complications among children undergoing allogeneic hematopoietic cell transplantation.

Complications following allogeneic hematopoietic cell transplantation (alloHCT) continue to be a significant challenge that often result in significant morbidity/mortality and increased healthcare utilization and cost. In this study, we analyzed the impact of post-alloHCT complications on healthcare utilization and cost during first year post-transplant. We analyzed data on 240 pediatric patients. Complications analyzed included kidney injury, liver injury, lung injury, viral infections, bacterial infections, fungal infections, and acute graft-versus-host disease (GVHD). Patients were divided into three groups based on the number of complications (0-1, 2-3, and >3). Cost was estimated from charges recorded in the Pediatric Health Information System database and hospital accounting records. Patients with >3 complications had higher healthcare utilization and cost, primarily driven by inpatient hospitalization and intensive care unit admissions. Multivariable analysis of risk factors identified bacteremia ($90,166, SE = 26,636, p < 0.001), lung injury ($108,529, SE = 28,196, p < 0.001), liver injury ($90,805, SE = 28,660, p = 0.002), and grade II-IV aGVHD ($137,866, SE = 28,472, p < 0.001) as associated with significantly increased cost. Our study highlights the significant impact complications have on the overall cost of alloHCT. The identification that complications associated with high morbidity (aGVHD, pulmonary disease) are also associated with the highest financial burden emphasizes the need for future research in these areas to expand management options and improve outcomes for our patients.

Health care utilization and cost among pediatric patients receiving unrelated donor allogeneic hematopoietic cell transplantation.

The costs associated with allogeneic hematopoietic cell transplantation (alloHCT) are high. Differences in costs and healthcare utilization among potential donor sources for alloHCT are not well characterized in pediatric recipients of alloHCT. One potential reason for these high costs could be the donor source of hematopoietic cells. In this retrospective study, inpatient costs, outpatient costs, and markers of healthcare utilization associated with unrelated donor alloHCT for malignant and non-malignant disease were analyzed for 131 pediatric patients during the first year post-transplant, for whom the donor sources were 38% umbilical cord blood (UCB), 14% unmanipulated peripheral blood stem cell (PBSC), 26% bone marrow (BM), and 22% PBSC with CD-34 selection. The median cost per day survived (through day +365) was lowest for patients receiving PBSC with CD-34 selection $926 (322-5316) as compared to UCB $1918 (491-107,93), unmanipulated PBSC $1516 (630-27,516), and BM $1205 (506-11,181) (p = 0.010). For non-malignant alloHCT, UCB had the highest costs per day survived $1530 (491-793) and PBSC with CD-34 selection had the lowest at $482 (322-3092) (p < 0.001). In a multivariable model for costs per day survived, high-risk disease (p = 0.009) and graft failure (p < 0.001) were significantly associated with higher cost and alloHCT between 2010 and 2015 as compared to 2005 and 2009 (p = 0.017) was significantly associated with lower cost per day survived. This study illustrates important differences in cost and healthcare utilization among the different donor sources used for unrelated alloHCT.

Asthma and subjective sleep disordered breathing in a large cohort of urban adolescents.

OBJECTIVE: Sleep disordered breathing (SDB) has not been well studied in urban adolescents with asthma in community settings. Nor has the association of SDB symptoms and asthma severity been studied. We characterized self-reported symptoms suggesting SDB and investigated the association of SDB symptoms, probable asthma, and asthma severity. METHODS: 9,565 adolescents from 21 inner-city high schools were screened for an asthma intervention study. Students reported on symptoms suggesting SDB using questions from the 2007 NHANES, if they were ever diagnosed with asthma, and on asthma symptoms. Using generalized linear mixed models with logit link with school as a random intercept and adjusting for age, gender, and race/ethnicity, we examined associations of SDB symptoms, and demographic characteristics, probable asthma, and asthma severity. RESULTS: 12% reported SDB symptoms. Older and bi-racial participants (compared to Caucasian) had higher odds of symptoms suggesting SDB (p <.001). Compared to those without probable asthma, adolescents with probable asthma had 2.63 greater odds of reporting SDB symptoms (p <.001). Among those with probable asthma, the odds of reporting SDB symptoms increased with asthma severity. When exploring daytime severity and severity due to night wakening separately, results were similar. All results remained significant when controlling for age, gender, and ethnicity. CONCLUSIONS: In a large urban community cohort of predominately ethnic minority adolescents, self-reported SDB symptoms were associated with probable asthma and increased asthma severity. This study highlights the importance of SDB as a modifiable co-morbidity of asthma.

MAPK signaling cascades mediate distinct glucocorticoid resistance mechanisms in pediatric leukemia.

The outcome for pediatric acute lymphoblastic leukemia (ALL) patients who relapse is dismal. A hallmark of relapsed disease is acquired resistance to multiple chemotherapeutic agents, particularly glucocorticoids. In this study, we performed a genome-scale short hairpin RNA screen to identify mediators of prednisolone sensitivity in ALL cell lines. The incorporation of these data with an integrated analysis of relapse-specific genetic and epigenetic changes allowed us to identify the mitogen-activated protein kinase (MAPK) pathway as a mediator of prednisolone resistance in pediatric ALL. We show that knockdown of the specific MAPK pathway members MEK2 and MEK4 increased sensitivity to prednisolone through distinct mechanisms. MEK4 knockdown increased sensitivity specifically to prednisolone by increasing the levels of the glucocorticoid receptor. MEK2 knockdown increased sensitivity to all chemotherapy agents tested by increasing the levels of p53. Furthermore, we demonstrate that inhibition of MEK1/2 with trametinib increased sensitivity of ALL cells and primary samples to chemotherapy in vitro and in vivo. To confirm a role for MAPK signaling in patients with relapsed ALL, we measured the activation of the MEK1/2 target ERK in matched diagnosis-relapse primary samples and observed increased phosphorylated ERK levels at relapse. Furthermore, relapse samples have an enhanced response to MEK inhibition compared to matched diagnosis samples in xenograft models. Together, our data indicate that inhibition of the MAPK pathway increases chemosensitivity to glucocorticoids and possibly other agents and that the MAPK pathway is an attractive target for prevention and/or treatment of relapsed disease.

Wnt inhibition leads to improved chemosensitivity in paediatric acute lymphoblastic leukaemia.

While childhood acute lymphoblastic leukaemia (ALL) is now highly curable, the dismal prognosis for children who relapse warrants novel therapeutic approaches. Previously, using an integrated genomic analysis of matched diagnosis-relapse paired samples, we identified overactivation of the Wnt pathway as a possible mechanism of recurrence. To validate these findings and document whether Wnt inhibition may sensitize cells to chemotherapy, we analysed the expression of activated ß-catenin (and its downstream target BIRC5) using multiparameter phosphoflow cytometry and tested the efficacy of a recently developed Wnt inhibitor, iCRT14, in ALL cell lines and patient samples. We observed increased activation of ß-catenin at relapse in 6/10 patients. Furthermore, treatment of leukaemic cell lines with iCRT14 led to significant downregulation of Wnt target genes and combination with traditional chemotherapeutic drugs resulted in a synergistic decrease in viability as well as a significant increase in apoptotic cell death. Finally, pre-treatment of purified blasts from patients with relapsed leukaemia with the Wnt inhibitor followed by exposure to prednisolone, restored chemosensitivity in these cells. Our results demonstrate that overactivation of the Wnt pathway may contribute to chemoresistance in relapsed childhood ALL and that Wnt-inhibition may be a promising therapeutic approach.

Loss of TBL1XR1 disrupts glucocorticoid receptor recruitment to chromatin and results in glucocorticoid resistance in a B-lymphoblastic leukemia model.

Although great advances have been made in the treatment of pediatric acute lymphoblastic leukemia, up to one of five patients will relapse, and their prognosis thereafter is dismal. We have previously identified recurrent deletions in TBL1XR1, which encodes for an F-box like protein responsible for regulating the nuclear hormone repressor complex stability. Here we model TBL1XR1 deletions in B-precursor ALL cell lines and show that TBL1XR1 knockdown results in reduced glucocorticoid receptor recruitment to glucocorticoid responsive genes and ultimately decreased glucocorticoid signaling caused by increased levels of nuclear hormone repressor 1 and HDAC3. Reduction in glucocorticoid signaling in TBL1XR1-depleted lines resulted in resistance to glucocorticoid agonists, but not to other chemotherapeutic agents. Importantly, we show that treatment with the HDAC inhibitor SAHA restores sensitivity to prednisolone in TBL1XR1-depleted cells. Altogether, our data indicate that loss of TBL1XR1 is a novel driver of glucocorticoid resistance in ALL and that epigenetic therapy may have future application in restoring drug sensitivity at relapse.