Low-affinity CAR T cells exhibit reduced trogocytosis, preventing fratricide and antigen-negative tumor escape while preserving anti-tumor activity

ABSTRACTChimeric antigen receptor (CAR) T cells using the high-affinity CD19 binding domain FMC63 are an effective treatment for patients with relapsed and aggressive B cell lymphoma. However, antigen loss and poor CAR T cell persistence remain common causes for relapse in these patients. Using primary patient samples, we now show that FMC63-based CAR T cells confer rapid antigen loss in all major tumor types currently approved for treatment with CD19 CAR T cells via trogocytosis, the stripping of antigen from tumor cells by CAR T cells. We show that CAR T cell-mediated trogocytosis can be dramatically reduced across a wide range of B cell malignancies by replacing FMC63 with a low affinity CD19 antibody. This reduction in trogocytosis does not alter the direct anti-tumor activity of CD19 CAR T cells but prevents the emergence of antigen-negative tumor cells and significantly increases CAR T cell viability by reducing fratricide of CD19 CAR T cells following trogocytosis.TEASERA reduction in CAR affinity does not affect tumor killing but prolongs T cell persistence and prevents antigen-negative tumor escape.

Challenges and Prospects for Designer T and NK Cells in Glioblastoma Immunotherapy

Glioblastoma (GBM) is the most prevalent, aggressive primary brain tumour with a dismal prognosis. Treatment at diagnosis has limited efficacy and there is no standardised treatment at recurrence. New, personalised treatment options are under investigation, although challenges persist for heterogenous tumours such as GBM. Gene editing technologies are a game changer, enabling design of novel molecular-immunological treatments to be used in combination with chemoradiation, to achieve long lasting survival benefits for patients. Here, we review the literature on how cutting-edge molecular gene editing technologies can be applied to known and emerging tumour-associated antigens to enhance chimeric antigen receptor T and NK cell therapies for GBM. A tight balance of limiting neurotoxicity, avoiding tumour antigen loss and therapy resistance, while simultaneously promoting long-term persistence of the adoptively transferred cells must be maintained to significantly improve patient survival. We discuss the opportunities and challenges posed by the brain contexture to the administration of the treatments and achieving sustained clinical responses.

Hypermethylation of CD19 promoter enables antigen-negative escape to CART-19 in vivo and in vitro

BackgroundAnti-CD19 chimeric antigen receptor T cells (CART-19) frequently induce remissions in hemato-oncological patients with recurred and/or refractory B-cell tumors. However, malignant cells sometimes escape the immunotherapeutic targeting by CD19 gene mutations, alternative splicing or lineage switch, commonly causing lack of CD19 expression on the surface of neoplastic cells. We assumed that, in addition to the known mechanisms, other means could act on CD19 to drive antigen-negative relapse.MethodsHerein, we studied the mechanism of antigen loss in an in vivo CD19-negative recurrence model of chronic lymphocytic leukemia (CLL) to CART-19, established using NOD-scid IL2Rgnull mice and HG3 cell line. We validated our findings in vitro in immortalized B-cell lines and primary CLL cells.ResultsIn our in vivo CLL recurrence model, up to 70% of CART-19-treated mice eventually recurred with CD19-negative disease weeks after initial positive response. We found that the lack of CD19 expression was caused by promoter DNA hypermethylation. Importantly, the expression loss was partially reversible by treatment with a demethylating agent. Moreover, this escape mechanism was common for 3 B-cell immortalized lines as well as primary CLL cells, as assessed by in vitro coculture experiments.ConclusionsEpigenetically driven antigen escape could represent a novel, yet at least partially reversible, means of CD19 loss to CART-19 in B-cell tumors.

Finite Antiviral Therapy in Chronic Hepatitis B Patients with Cirrhosis

Antiviral therapy has greatly improved the survival and reduced the incidence of adverse liver events such as hepatic decompensation and hepatocellular carcinoma in chronic hepatitis B patients with cirrhosis (hepatitis B virus [HBV]-cirrhosis). However, hepatitis B surface antigen loss, regarded as the ultimate goal of therapy or functional cure, was rarely achieved during long-term indefinite nucleos(t)ide analogues (Nuc) treatment. Emerging issues such as medication adherence and loss-to-follow-up may lead to increased risk of hepatic decompensation, even catastrophic life-threatening events. Studies have shown that finite therapy is feasible and reasonably safe, even in patients with HBV-cirrhosis. This review critically assesses the scientific evidence of the pros and cons for finite Nuc therapy in HBV-cirrhosis and proposes how to stop Nuc therapy and monitor the off-therapy patients. It also proposes the perspective and unsolved issues to be investigated in the future.

Thin-Film Freeze-Drying of a Norovirus Vaccine Candidate

A bivalent Norovirus vaccine candidate has been developed that contains Norovirus strain GI.1 Norwalk-virus like particles (VLP) and strain GII.4 Consensus VLP adsorbed onto aluminum (oxy)hydroxide. In the present study, we tested the feasibility of converting the vaccine from a liquid suspension into dry powder by thin-film freeze-drying (TFFD). With the proper amount of trehalose and/or sucrose as cryoprotectant, TFFD can be applied to transform the Norovirus vaccine candidate into dry powders without causing antigen loss or particle aggregation, while maintaining the potency of the antigens within a specified acceptable range. In an accelerated stability study, the potency of the antigens was also maintained in the specified acceptable range after the dry powders were stored for eight weeks at 40 oC, 75% relative humidity. The dry powder Norovirus vaccine offers the potential to eliminate the cold chain requirement for transport and/or storage of the vaccine.