Background
Denintuzumab mafodotin (SGN‐CD19A) is a CD19‐targeting antibody‐drug conjugate, comprising a monoclonal antibody conjugated to the potent cytotoxin monomethyl auristatin F. Since ...denintuzumab mafodotin has previously shown activity against B‐cell malignancies in early‐stage clinical trials, it was of interest to test it against the Pediatric Preclinical Testing Program preclinical models of CD19+ pediatric acute lymphoblastic leukemia (ALL).
Procedures
Denintuzumab mafodotin was evaluated against eight B‐cell lineage ALL patient‐derived xenografts (PDXs), representing B‐cell precursor ALL, Ph‐like ALL, and mixed‐lineage leukemia rearranged infant ALL. Denintuzumab mafodotin was administered weekly for 3 weeks at 3 mg/kg. It was also tested in combination with an induction‐type chemotherapy regimen of vincristine, dexamethasone, and l‐asparaginase (VXL) against three PDXs. The relationship between cell surface and gene expression of CD19 and drug activity was also assessed.
Results
Denintuzumab mafodotin significantly delayed the progression of seven of eight PDXs tested and achieved objective responses in five of eight. There was no apparent subtype specificity of denintuzumab mafodotin activity. No correlations were observed between CD19 mRNA or cell surface expression and denintuzumab mafodotin activity, perhaps due to small sample size, and denintuzumab mafodotin treatment did not select for reduced CD19 expression. Combining denintuzumab mafodotin with VXL achieved therapeutic enhancement compared to either treatment alone.
Conclusions
Denintuzumab mafodotin showed single‐agent activity against selected B‐lineage ALL PDXs, although leukemia growth was evident in most models at 28 days from treatment initiation. This level of activity for denintuzumab mafodotin is consistent with that observed in adults with ALL.
Biomarkers which better match anticancer drugs with cancer driver genes hold the promise of improved clinical responses and cure rates. We developed a precision medicine platform of rapid ...high‐throughput drug screening (HTS) and patient‐derived xenografting (PDX) of primary tumor tissue, and evaluated its potential for treatment identification among 56 consecutively enrolled high‐risk pediatric cancer patients, compared with conventional molecular genomics and transcriptomics. Drug hits were seen in the majority of HTS and PDX screens, which identified therapeutic options for 10 patients for whom no targetable molecular lesions could be found. Screens also provided orthogonal proof of drug efficacy suggested by molecular analyses and negative results for some molecular findings. We identified treatment options across the whole testing platform for 70% of patients. Only molecular therapeutic recommendations were provided to treating oncologists and led to a change in therapy in 53% of patients, of whom 29% had clinical benefit. These data indicate that in vitro and in vivo drug screening of tumor cells could increase therapeutic options and improve clinical outcomes for high‐risk pediatric cancer patients.
Synopsis
A precision diagnostic platform integrating genomics and transcriptomics with drug testing of patient's primary tumor cells in high throughput drug screening (HTS) and patient‐derived xenograft (PDX) was established to improve identification of therapies in high‐risk pediatric cancer patients.
Treatment options could be identified for 70% of patients across the four‐part platform.
HTS provided orthogonal proof of drug efficacy suggested by molecular analyses and identified many new drug responses without prior molecular hallmarks.
Effective treatments were observed in more than half of PDX models.
There was a strong correlation between HTS and PDX results, and the clinical responses in patients.
A precision diagnostic platform integrating genomics and transcriptomics with drug testing of patient's primary tumor cells in high throughput drug screening (HTS) and patient‐derived xenograft (PDX) was established to improve identification of therapies in high‐risk pediatric cancer patients.
Although the overall cure rate for pediatric acute lymphoblastic leukemia (ALL) approaches 90%, infants with ALL harboring translocations in the mixed-lineage leukemia (MLL) oncogene (infant MLL-ALL) ...experience shorter remission duration and lower survival rates (∼50%). Mutations in the p53 tumor-suppressor gene are uncommon in infant MLL-ALL, and drugs that release p53 from inhibitory mechanisms may be beneficial. The purpose of this study was to assess the efficacy of the orally available nutlin, RG7112, against patient-derived MLL-ALL xenografts.
Eight MLL-ALL patient-derived xenografts were established in immune-deficient mice, and their molecular features compared with B-lineage ALL and T-ALL xenografts. The sensitivity of MLL-ALL xenografts to RG7112 was assessed in vitro and in vivo, and the ability of RG7112 to induce p53, cell-cycle arrest, and apoptosis in vivo was evaluated.
Gene-expression analysis revealed that MLL-ALL, B-lineage ALL, and T-ALL xenografts clustered according to subtype. Moreover, genes previously reported to be overexpressed in MLL-ALL, including MEIS1, CCNA1, and members of the HOXA family, were significantly upregulated in MLL-ALL xenografts, confirming their ability to recapitulate the clinical disease. Exposure of MLL-ALL xenografts to RG7112 in vivo caused p53 upregulation, cell-cycle arrest, and apoptosis. RG7112 as a single agent induced significant regressions in infant MLL-ALL xenografts. Therapeutic enhancement was observed when RG7112 was assessed using combination treatment with an induction-type regimen (vincristine/dexamethasone/L-asparaginase) against an MLL-ALL xenograft.
The utility of targeting the p53-MDM2 axis in combination with established drugs for the management of infant MLL-ALL warrants further investigation.
Glucocorticoids play a critical role in the therapy of lymphoid malignancies, including pediatric acute lymphoblastic leukemia (ALL), although the mechanisms underlying cellular resistance remain ...unclear. We report glucocorticoid resistance attributable to epigenetic silencing of the BIM gene in pediatric ALL biopsies and xenografts established in immune-deficient mice from direct patient explants as well as a therapeutic approach to reverse resistance in vivo. Glucocorticoid resistance in ALL xenografts was consistently associated with failure to up-regulate BIM expression after dexamethasone exposure despite confirmation of a functional glucocorticoid receptor. Although a comprehensive assessment of BIM CpG island methylation revealed no consistent changes, glucocorticoid resistance in xenografts and patient biopsies significantly correlated with decreased histone H3 acetylation. Moreover, the histone deacetylase inhibitor vorinostat relieved BIM repression and exerted synergistic antileukemic efficacy with dexamethasone in vitro and in vivo. These findings provide a novel therapeutic strategy to reverse glucocorticoid resistance and improve outcome for high-risk pediatric ALL.
•Ixazomib is an orally available, reversible selective proteasome inhibitor•Ixazomib elicited IC50 values in the low nanomolar range in T-ALL cell models in vitro•Ixazomib treatment of PDX models in ...vivo resulted in a modest increase in survival
The overall survival rate of patients with T-cell acute lymphoblastic leukemia (T-ALL) is now 90%, although patients with relapsed T-ALL face poor prognosis. The ubiquitin–proteasome system maintains normal protein homeostasis, and aberrations in this pathway are associated with T-ALL. Here we demonstrate the in vitro and in vivo activity of ixazomib, a second-generation orally available, reversible, and selective proteasome inhibitor against pediatric T-ALL cell lines and patient-derived xenografts (PDXs) grown orthotopically in immunodeficient NOD.Cg-PrkdcscidIL2rgtm1Wjl/SzJAusb (NSG) mice. Ixazomib was highly potent in vitro, with half-maximal inhibitory concentration (IC50) values in the low nanomolar range. As a monotherapy, ixazomib significantly extended mouse event-free survival of five out of eight T-ALL PDXs in vivo.
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