Factors associated with outcomes after a second CD19-targeted CAR T-cell infusion for refractory B-cell malignancies.

CD19-targeted chimeric antigen receptor-engineered (CD19 CAR) T-cell therapy has shown significant efficacy for relapsed or refractory (R/R) B-cell malignancies. Yet, CD19 CAR T cells fail to induce durable responses in most patients. Second infusions of CD19 CAR T cells (CART2) have been considered as a possible approach to improve outcomes. We analyzed data from 44 patients with R/R B-cell malignancies (acute lymphoblastic leukemia [ALL], n = 14; chronic lymphocytic leukemia [CLL], n = 9; non-Hodgkin lymphoma [NHL], n = 21) who received CART2 on a phase 1/2 trial (NCT01865617) at our institution. Despite a CART2 dose increase in 82% of patients, we observed a low incidence of severe toxicity after CART2 (grade ≥3 cytokine release syndrome, 9%; grade ≥3 neurotoxicity, 11%). After CART2, complete response (CR) was achieved in 22% of CLL, 19% of NHL, and 21% of ALL patients. The median durations of response after CART2 in CLL, NHL, and ALL patients were 33, 6, and 4 months, respectively. Addition of fludarabine to cyclophosphamide-based lymphodepletion before the first CAR T-cell infusion (CART1) and an increase in the CART2 dose compared with CART1 were independently associated with higher overall response rates and longer progression-free survival after CART2. We observed durable CAR T-cell persistence after CART2 in patients who received cyclophosphamide and fludarabine (Cy-Flu) lymphodepletion before CART1 and a higher CART2 compared with CART1 cell dose. The identification of 2 modifiable pretreatment factors independently associated with better outcomes after CART2 suggests strategies to improve in vivo CAR T-cell kinetics and responses after repeat CAR T-cell infusions, and has implications for the design of trials of novel CAR T-cell products after failure of prior CAR T-cell immunotherapies.

Cell-intrinsic abrogation of TGF-ß signaling delays but does not prevent dysfunction of self/tumor-specific CD8 T cells in a murine model of autochthonous prostate cancer.

Adoptive T cell therapy (ACT) for the treatment of established cancers is actively being pursued in clinical trials. However, poor in vivo persistence and maintenance of antitumor activity of transferred T cells remain major problems. TGF-ß is a potent immunosuppressive cytokine that is often expressed at high levels within the tumor microenvironment, potentially limiting T cell-mediated antitumor activity. In this study, we used a model of autochthonous murine prostate cancer to evaluate the effect of cell-intrinsic abrogation of TGF-ß signaling in self/tumor-specific CD8 T cells used in ACT to target the tumor in situ. We found that persistence and antitumor activity of adoptively transferred effector T cells deficient in TGF-ß signaling were significantly improved in the cancerous prostate. However, over time, despite persistence in peripheral lymphoid organs, the numbers of transferred cells in the prostate decreased and the residual prostate-infiltrating T cells were no longer functional. These findings reveal that TGF-ß negatively regulates the accumulation and effector function of transferred self/tumor-specific CD8 T cells and highlight that, when targeting a tumor Ag that is also expressed as a self-protein, additional substantive obstacles are operative within the tumor microenvironment, potentially hampering the success of ACT for solid tumors.

Preclinical and translational pharmacology of afucosylated anti-CCR8 antibody for depletion of tumour-infiltrating regulatory T cells.

BACKGROUND AND PURPOSE: RO7502175 is an afucosylated antibody designed to eliminate C-C motif chemokine receptor 8 (CCR8)+ Treg cells in the tumour microenvironment through enhanced antibody-dependent cellular cytotoxicity (ADCC). EXPERIMENTAL APPROACH: We report findings from preclinical studies characterizing pharmacology, pharmacokinetics (PK)/pharmacodynamics (PD) and safety profile of RO7502175 and discuss the translational PK/PD approach used to inform first-in-human (FiH) dosing strategy and clinical development in solid tumour indications. KEY RESULTS: RO7502175 demonstrated selective ADCC against human CCR8+ Treg cells from dissociated tumours in vitro. In cynomolgus monkeys, RO7502175 exhibited a biphasic concentration-time profile consistent with immunoglobulin G1 (IgG1) antibodies, reduced CCR8+ Treg cells in the blood, induced minimal and transient cytokine secretion, and was well tolerated with a no-observed-adverse-effect level (NOAEL) of 100 mg·kg-1. Moreover, RO7502175 caused minimal cytokine release from peripheral blood mononuclear cells (PBMCs) in vitro. A quantitative model was developed to capture surrogate anti-murine CCR8 antibody PK/PD and tumour dynamics in mice and RO7502175 PK/PD in cynomolgus monkeys. Subsequently, the model was used to project RO7502175 human PK and receptor occupancy (RO) in patients. Because traditional approaches resulted in a low FiH dose for this molecule, even with its superior preclinical safety profile, an integrated approach based on the totality of preclinical data and modelling insights was used for starting dose selection. CONCLUSION AND IMPLICATIONS: This work demonstrates a translational research strategy for collecting and utilizing relevant nonclinical data, developing a mechanistic PK/PD model and using a comprehensive approach to inform clinical study design for RO7502175.

A novel polymer-conjugated human IL-15 improves efficacy of CD19-targeted CAR T-cell immunotherapy.

Chimeric antigen receptor (CAR)-modified T-cell therapies targeting CD19 represent a new treatment option for patients with relapsed/refractory (R/R) B-cell malignancies. However, CAR T-cell therapy fails to elicit durable responses in a significant fraction of patients. Limited in vivo proliferation and survival of infused CAR T cells are key causes of failure. In a phase 1/2 clinical trial of CD19 CAR T cells for B-cell malignancies (#NCT01865617), low serum interleukin 15 (IL-15) concentration after CAR T-cell infusion was associated with inferior CAR T-cell kinetics. IL-15 supports T-cell proliferation and survival, and therefore, supplementation with IL-15 may enhance CAR T-cell therapy. However, the clinical use of native IL-15 is challenging because of its unfavorable pharmacokinetic (PK) and toxicity. NKTR-255 is a polymer-conjugated IL-15 that engages the entire IL-15 receptor complex (IL-15Rα/IL-2Rßγ) and exhibits reduced clearance, providing sustained pharmacodynamic (PD) responses. We investigated the PK and immune cell PDs in nonhuman primates treated with NKTR-255 and found that NKTR-255 enhanced the in vivo proliferation of T cells and natural killer cells. In vitro, NKTR-255 induced dose-dependent proliferation and accumulation of human CD19 CAR T cells, especially at low target cell abundance. In vivo studies in lymphoma-bearing immunodeficient mice demonstrated enhanced antitumor efficacy of human CD19 CAR T cells. In contrast to mice treated with CAR T cells alone, those that received CAR T cells and NKTR-255 had markedly higher CAR T-cell counts in the blood and marrow that were sustained after tumor clearance, without evidence of persistent proliferation or ongoing activation/exhaustion as assessed by Ki-67 and inhibitory receptor coexpression. These data support an ongoing phase 1 clinical trial of combined therapy with CD19 CAR T cells and NKTR-255 for R/R B-cell malignancies.

Mesothelin is a novel cell surface disease marker and potential therapeutic target in acute myeloid leukemia.

In an effort to identify acute myeloid leukemia (AML)-restricted targets for therapeutic development in AML, we analyzed the transcriptomes of 2051 children and young adults with AML and compared the expression profile with normal marrow specimens. This analysis identified a large cohort of AML-restricted genes with high expression in AML, but low to no expression in normal hematopoiesis. Mesothelin (MSLN), a known therapeutic target in solid tumors, was shown to be highly overexpressed in 36% of the AML cohort (range, 5-1077.6 transcripts per million [TPM]) and virtually absent in normal marrow (range, 0.1-10.7 TPM). We verified MSLN transcript expression by quantitative reverse transcription polymerase chain reaction, confirmed cell surface protein expression on leukemic blasts by multidimensional flow cytometry, and demonstrated that MSLN expression was associated with promoter hypomethylation. MSLN was highly expressed in patients with KMT2A rearrangements (P < .001), core-binding factor fusions [inv(16)/t(16;16), P < .001; t(8;21), P < .001], and extramedullary disease (P = .001). We also demonstrated the presence of soluble MSLN in diagnostic serum specimens using an MSLN-directed enzyme-linked immunosorbent assay. In vitro and in vivo preclinical efficacy of the MSLN-directed antibody-drug conjugates (ADCs) anetumab ravtansine and anti-MSLN-DGN462 were evaluated in MSLN+ leukemia cell lines in vitro and in vivo, as well as in patient-derived xenografts. Treatment with ADCs resulted in potent target-dependent cytotoxicity in MSLN+ AML. In this study, we demonstrate that MSLN is expressed in a significant proportion of patients with AML and holds significant promise as a diagnostic and therapeutic target in AML, and that MSLN-directed therapeutic strategies, including ADCs, warrant further clinical investigation.

Assessment and management of cytokine release syndrome and neurotoxicity following CD19 CAR-T cell therapy.

Introduction: The success of CD19 chimeric antigen receptor (CAR)-T cell therapy for treatment of CD19 positive malignancies has led to the FDA approval of two CD19 CAR-T cell products, tisagenlecleucel and axicabtagene ciloleucel, and ongoing clinical trials of new products. Cytokine release syndrome (CRS) and neurotoxicity are common toxicities associated with CD19 CAR-T cell therapies.Areas covered: This review will discuss CRS and neurotoxicity associated with CD19 CAR-T cell therapies, including clinical presentation, risk factors, pathophysiology, and therapeutic or prophylactic interventions.Expert opinion: In conjunction with improved understanding of the pathophysiology of CRS and neurotoxicity, we expect that the recent development of consensus guidelines for the evaluation of these toxicities will enhance management of patients undergoing CD19 CAR-T cell therapies.

Insight into mechanisms associated with cytokine release syndrome and neurotoxicity after CD19 CAR-T cell immunotherapy.

Adoptive immunotherapy with CD19-targeted chimeric antigen receptor (CAR)-T cells has been successful in producing durable remissions in some patients with relapsed or refractory B cell malignancies. Despite the efficacy of CAR-T cell therapy, significant toxicities can occur. Cytokine release syndrome (CRS) and neurotoxicity are the most common toxicities and can range from self-limited fever to life threatening organ damage and death. Understanding the mechanisms underlying these toxicities can help guide and improve outcomes. In this review we describe CRS and neurotoxicity in patients with B cell malignancies treated with CD19 CAR-T cells in pivotal trials, and also provide insight into potential mechanisms associated with these toxicities based on studies conducted in a phase 1/2 clinical trial at the Fred Hutchinson Cancer Research Center.

Functional profiling of a human cytomegalovirus genome.

Human cytomegalovirus (HCMV), a ubiquitous herpesvirus, causes a lifelong subclinical infection in healthy adults but leads to significant morbidity and mortality in neonates and immunocompromised individuals. Its ability to grow in different cell types is responsible for HCMV-associated diseases, including mental retardation and retinitis, and vascular disorders. To globally assess viral gene function for replication in cells, we determined the genomic sequence of a bacterial artificial chromosome (BAC)-based clone of HCMV Towne strain and used this information to delete each of its 162 unique ORFs and generate a collection of viral mutants. The growth of these mutants in different cultured cells was examined to systematically investigate the necessity of each ORF for replication. Our results showed that 45 ORFs are essential for viral replication in fibroblasts and 117 are nonessential. Some genes were found to be required for viral replication in retinal pigment epithelial cells and microvascular endothelial cells, but not in fibroblasts, indicating their role as tropism factors. Interestingly, several viral mutants grew 10- to 500-fold better than the parental strain in different cell types, suggesting that the deleted ORFs encode replication temperance or repressing functions. Thus, HCMV encodes supportive and suppressive growth regulators for optimizing its replication in human fibroblasts, epithelial, and endothelial cells. Suppression of viral replication by virus-encoded temperance factors represents a novel mechanism for regulating the growth of an animal virus, and may contribute to HCMV's optimal infection of different tissues and successful proliferation among the human population.