Bortezomib-based four-drug induction does induce a response in advanced relapsed ALL but cure remains elusive

Phase 2 study of combination chemotherapy with bortezomib in children with relapsed and refractory acute lymphoblastic leukemia

Treatment outcomes for children with relapsed and refractory acute lymphoblastic leukemia (R/R-ALL) remain poor, and the optimal induction therapy has not been determined. Bortezomib is a proteasome inhibitor that acts synergistically and additively with standard chemotherapy for ALL. We evaluated the efficacy and safety of combination chemotherapy with bortezomib in children with R/R-ALL. This single-arm, multicenter, phase 2 study was conducted in Japan between 2016 and 2020. Eligible patients were divided into two cohorts: a high-risk first-relapse cohort of untreated patients with high-risk first-relapsed ALL and an expansion cohort of patients with refractory ALL, including multiple relapses, relapse after allogeneic hematopoietic cell transplantation, and induction failure. All patients received a single course of chemotherapy as induction therapy. Sixteen patients (10 in the high-risk first-relapse cohort, six in the expansion cohort) were evaluable. The overall remission rate after induction therapy was 60% in the high-risk first-relapse cohort and 16.7% in the expansion cohort. All patients had minimal residual disease. Adverse events were acceptable except for interstitial lung disease and hypoxia in a patient in the expansion cohort, but addition of bortezomib to conventional chemotherapy did not produce obvious improvement in children with R/R-ALL.

Therapeutic Targeting of the Leukaemia Microenvironment

In recent decades, the conduct of uniform prospective clinical trials has led to improved remission rates and survival for patients with acute myeloid leukaemia and acute lymphoblastic leukaemia. However, high-risk patients continue to have inferior outcomes, where chemoresistance and relapse are common due to the survival mechanisms utilised by leukaemic cells. One such mechanism is through hijacking of the bone marrow microenvironment, where healthy haematopoietic machinery is transformed or remodelled into a hiding ground or "sanctuary" where leukaemic cells can escape chemotherapy-induced cytotoxicity. The bone marrow microenvironment, which consists of endosteal and vascular niches, can support leukaemogenesis through intercellular "crosstalk" with niche cells, including mesenchymal stem cells, endothelial cells, osteoblasts, and osteoclasts. Here, we summarise the regulatory mechanisms associated with leukaemia-bone marrow niche interaction and provide a comprehensive review of the key therapeutics that target CXCL12/CXCR4, Notch, Wnt/b-catenin, and hypoxia-related signalling pathways within the leukaemic niches and agents involved in remodelling of niche bone and vasculature. From a therapeutic perspective, targeting these cellular interactions is an exciting novel strategy for enhancing treatment efficacy, and further clinical application has significant potential to improve the outcome of patients with leukaemia.

Preclinical Evaluation of Carfilzomib for Infant KMT2A-Rearranged Acute Lymphoblastic Leukemia

BACKGROUND

Infants with KMT2A-rearranged B-cell precursor acute lymphoblastic leukemia (ALL) have poor outcomes. There is an urgent need to identify novel agents to improve survival. Proteasome inhibition has emerged as a promising therapeutic strategy for several hematological malignancies. The aim of this study was to determine the preclinical efficacy of the selective proteasome inhibitor carfilzomib, for infants with KMT2A-rearranged ALL.

METHODS

Eight infant ALL cell lines were extensively characterized for immunophenotypic and cytogenetic features. In vitro cytotoxicity to carfilzomib was assessed using a modified Alamar Blue assay with cells in logarithmic growth. The Bliss Independence model was applied to determine synergy between carfilzomib and the nine conventional chemotherapeutic agents used to treat infants with ALL. Established xenograft models were used to identify the maximal tolerated dose of carfilzomib and determine in vivo efficacy.

RESULTS

Carfilzomib demonstrated low IC50 concentrations within the nanomolar range (6.0-15.8 nm) across the panel of cell lines. Combination drug testing indicated in vitro synergy between carfilzomib and several conventional chemotherapeutic agents including vincristine, daunorubicin, dexamethasone, L-asparaginase, and 4-hydroperoxycyclophosphamide. In vivo assessment did not lead to a survival advantage for either carfilzomib monotherapy, when used to treat both low or high disease burden, or for carfilzomib in combination with multi-agent induction chemotherapy comprising of vincristine, dexamethasone, and L-asparaginase.

CONCLUSIONS

Our study highlights that in vitro efficacy does not necessarily translate to benefit in vivo and emphasizes the importance of in vivo validation prior to suggesting an agent for clinical use. Whilst proteasome inhibitors have an important role to play in several hematological malignancies, our findings guard against prioritization of carfilzomib for treatment of KMT2A-rearranged infant ALL in the clinical setting.

Case Report: Humanized Selective CD19CAR-T Treatment Induces MRD-Negative Remission in a Pediatric B-ALL Patient With Primary Resistance to Murine-Based CD19CAR-T Therapy

Background

CD19 chimeric antigen receptor T cell (CD19CAR-T) has shown great potential to treat acute B cell lymphoblastic leukemia (B-ALL) and B cell lymphoma, and most of anti-CD19 scFv are derived from murine antibody sequences. However, about 10–20% of B-ALL patients exhibit primary resistance to murine-based CD19CAR-T (CD19mCAR-T). Herein, we report that a humanized selective CD19CAR-T (CD19hsCAR-T) may offer a solution to this problem.

Case Description

A 10-year old boy was diagnosed with high-risk B-ALL in Mar., 2013, and relapsed in Oct., 2018, after he underwent haplo-identical hematopoietic stem cell transplantation (HSCT) in 2017. The patient then received haplo-identical CD19mCAR-T infusions twice following induction chemotherapy with Vincristine, Dexamethasone and Asparaginase (VDL), but no response was observed. We further treated this patient with CD19hsCAR-T following chemotherapy with Vindesine, Idarubicin, Dexamethasone, and Pegylated Asparaginase (VDLD) plus bortezomib. The patient achieved minimal residual disease-negative (MRDneg) complete remission with incomplete hematopoietic recovery (CRi), and remained in CRi for more than 8 months with manageable side effect. The patient, unfortunately, died of unidentified pulmonary infection on Jan. 25 2020.

Conclusion

CD19hsCAR-T may have the potential to induce remission in patients who are primarily refractory to CD19mCAR-T.