Beyond CD19: Opportunities for Future Development of Targeted Immunotherapy in Pediatric Relapsed-Refractory Acute Leukemia

Chimeric antigen receptor (CAR) T cell therapy has been used as a targeted approach in cancer therapy. Relapsed and refractory acute leukemia in pediatrics has been difficult to treat with conventional therapy due to dose limiting toxicities. With the recent success of CD 19 CAR in pediatric patients with B cell ALL, this mode of therapy has become a very attractive option for these patients with high risk disease. In this review, we will discuss current treatment paradigms of pediatric acute leukemia, and potential therapeutic targets for additional high risk populations, including T cell ALL, AML, and infant ALL

Prolonged Complete Response in a Pediatric Patient With Primary Peripheral T-Cell Lymphoma of the Central Nervous System.

We describe a child with a 2-week history of progressive headaches, blurry vision, and intermittent vomiting. Magnetic resonance imaging (MRI) of the brain showed a deep left hemispheric lesion with extension into the corpus callosum. Histology and immunophenotyping of the lesion was consistent with peripheral T-cell lymphoma, not otherwise specified. Chemotherapy was initiated and a complete remission was achieved. This case illustrates that a chemotherapeutic regimen used in adults with central nervous system (CNS) lymphoma can achieve durable remissions in pediatric patients with peripheral T-cell lymphoma, not otherwise specified of the CNS

Invasive fusariosis masquerading as extramedullary disease in rapidly progressive acute lymphoblastic leukemia

Invasive fusariosis (IF) most commonly occurs in patients with hematologic malignancies and severe neutropenia, particularly during concomitant corticosteroid use. Breakthrough infections can occur in high-risk patients despite Aspergillus-active antifungal prophylaxis. We describe a patient with rapid acute lymphoblastic leukemia (ALL) progression who presented with multifocal skin nodules thought to be choloromatous disease. These lesions were ultimately diagnosed as IF and the patient had two simultaneously active disease processes. This case highlights the importance of pathologic diagnosis of new skin lesions in ALL patients, even during leukemia progression, and demonstrates that IF can occur despite normal neutrophil counts and Aspergillus-active prophylaxis

Perforin-deficient CAR T cells recapitulate late-onset inflammatory toxicities observed in patients

Late-onset inflammatory toxicities resembling hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS) occur after chimeric antigen receptor T cell (CAR T cell) infusion and represent a therapeutic challenge. Given the established link between perforin deficiency and primary HLH, we investigated the role of perforin in anti-CD19 CAR T cell efficacy and HLH-like toxicities in a syngeneic murine model. Perforin contributed to both CD8+ and CD4+ CAR T cell cytotoxicity but was not required for in vitro or in vivo leukemia clearance. Upon CAR-mediated in vitro activation, perforin-deficient CAR T cells produced higher amounts of proinflammatory cytokines compared with WT CAR T cells. Following in vivo clearance of leukemia, perforin-deficient CAR T cells reexpanded, resulting in splenomegaly with disruption of normal splenic architecture and the presence of hemophagocytes, which are findings reminiscent of HLH. Notably, a substantial fraction of patients who received anti-CD22 CAR T cells also experienced biphasic inflammation, with the second phase occurring after the resolution of cytokine release syndrome, resembling clinical manifestations of HLH. Elevated inflammatory cytokines such as IL-1β and IL-18 and concurrent late CAR T cell expansion characterized the HLH-like syndromes occurring in the murine model and in humans. Thus, a murine model of perforin-deficient CAR T cells recapitulated late-onset inflammatory toxicities occurring in human CAR T cell recipients, providing therapeutically relevant mechanistic insights

A Comprehensive Analysis of Adverse Events in the First 30 Days of Phase 1 Pediatric CAR T-Cell Trials

The tremendous success of chimeric antigen receptor (CAR) T-cells in children and young adults (CAYA) with relapsed/refractory B-cell acute lymphoblastic leukemia is tempered by toxicities such as cytokine release syndrome (CRS). Despite expansive information about CRS, profiling of specific end-organ toxicities secondary to CAR T-cell therapy in CAYAs is limited. This retrospective, single-center study sought to characterize end-organ specific adverse events (AEs) experienced by CAYAs during the first 30 days following CAR T-cell infusion. AEs graded using Common Terminology Criteria for Adverse Events (CTCAE) were collected on 134 patients enrolled on one of three phase 1 CAR T-cell trials (NCT01593696, NCT02315612, and NCT03448393), targeting CD19 and/or CD22. A total of 133 (99.3%) patients experienced at least 1 \u3e grade 3 (Gr3) AE across 17 organ systems, 75 (4.4%) of which were considered dose or treatment limiting toxicities. Excluding cytopenias, 109 (81.3%) patients experienced a median of 3 \u3eGr3 non-cytopenia (NC) AEs. The incidence of \u3eGr3 NC AEs was associated with development (p \u3c0.0001) and severity (p=0.0002) of CRS as well as pre-infusion disease burden (\u3e 25% marrow blasts; p \u3c0.0001). While those with complete remission trended toward experiencing more \u3eGr3 NC AEs than non-responders, (median 4 versus 3, p=0.10), non-responders experiencing CRS (n=17, 37.8%) had the highest degree of NC AEs across all patients (median 7 versus 4 in responders experiencing CRS, p=0.07). Greater understanding of these toxicities and the ability to predict which patients may experience more toxicities is critical as the array of CAR T-cell therapies expand. Clinical Trial # NCT01593696, NCT03448393