Development of a B-cell maturation antigen-specific T-cell antigen coupler receptor for multiple myeloma

Strategies for modifying the chimeric antigen receptor (CAR) to improve safety and reduce toxicity in CAR T cell therapy for cancer

Immune cell therapy with chimeric antigen receptor (CAR) T cells, which has shown promising efficacy in patients with some hematologic malignancies, has introduced several successfully approved CAR T cell therapy products. Nevertheless, despite significant advances, treatment with these products has major challenges regarding potential toxicity and sometimes fatal adverse effects for patients. These toxicities can result from cytokine release or on-target off-tumor toxicity that targets healthy host tissue following CAR T cell therapy. The present study focuses on the unexpected side effects of targeting normal host tissues with off-target toxicity. Also, recent safety strategies such as replacing or adding different components to CARs and redesigning CAR structures to eliminate the toxic impact of CAR T cells, including T cell antigen coupler (TAC), switch molecules, suicide genes, and humanized monoclonal antibodies in the design of CARs, are discussed in this review.

Constitutive expression of interleukin-27 diminishes proinflammatory cytokine production without impairing effector function of engineered T cells

Immunomodulatory cytokines can alter the tumor microenvironment and promote tumor eradication. Interleukin (IL)-27 is a pleiotropic cytokine that has potential to augment anti-tumor immunity while also facilitating anti-myeloma activity. We engineered human T cells to express a recombinant single-chain (sc)IL-27 and a synthetic antigen receptor targeting the myeloma antigen, B-cell maturation antigen, and evaluated the anti-tumor function of T cells bearing scIL-27 in vitro and in vivo. We discovered that T cells bearing scIL-27 sustained anti-tumor immunity and cytotoxicity yet manifested a profound reduction in pro-inflammatory cytokines granulocyte-macrophage colony-stimulating factor and tumor necrosis factor alpha. IL-27-expressing T cells therefore present a potential avenue to avert treatment-related toxicities commonly associated with engineered T-cell therapy due to the reduced pro-inflammatory cytokine profile.

T-cell engineered with a fully humanized B-cell maturation antigen-specific T-cell antigen coupler receptor effectively target multiple myeloma

B-cell maturation antigen (BCMA) is a clinically validated target for multiple myeloma. T-cell engineered with chimeric antigen receptors (CARs) directed against BCMA have demonstrated robust therapeutic activity in clinical trials, but toxicities remain a significant concern for a subset of patients, supporting continued investigation of other engineered T-cell platforms that may offer equal efficacy with an improved toxicity profile. The authors recently described a BCMA-specific, T-cell-centric synthetic antigen receptor, the T-cell antigen coupler (TAC) receptor, that can be used to engineer T-cell with robust anti-myeloma activity. Here the authors describe the creation of a fully humanized BCMA-specific TAC receptor. Single-chain variable fragments (scFvs) were developed from BCMA-specific F(ab)s that were identified in a fully human phage display library. Twenty-four configurations of the F(ab)s were evaluated in a medium-throughput screening using primary T-cell, and a single F(ab), TRAC 3625, emerged as the most robust following in vitro and in vivo evaluation. An optimized BCMA-specific TAC receptor was developed through iterations of the BCMA-TAC design that evaluated a next-generation TAC scaffold sequence, different domains connecting the TAC to the 3625 scFv and different orientations of the TRAC 3625 heavy and light variable regions.

LCL161 enhances expansion and survival of engineered anti-tumor T cells but is restricted by death signaling

Background

The genesis of SMAC mimetic drugs is founded on the observation that many cancers amplify IAP proteins to facilitate their survival, and therefore removal of these pathways would re-sensitize the cells towards apoptosis. It has become increasingly clear that SMAC mimetics also interface with the immune system in a modulatory manner. Suppression of IAP function by SMAC mimetics activates the non-canonical NF-κB pathway which can augment T cell function, opening the possibility of using SMAC mimetics to enhance immunotherapeutics.

Methods

We have investigated the SMAC mimetic LCL161, which promotes degradation of cIAP-1 and cIAP-2, as an agent for delivering transient costimulation to engineered BMCA-specific human TAC T cells. In doing so we also sought to understand the cellular and molecular effects of LCL161 on T cell biology.

Results

LCL161 activated the non-canonical NF-κB pathway and enhanced antigen-driven TAC T cell proliferation and survival. Transcriptional profiling from TAC T cells treated with LCL161 revealed differential expression of costimulatory and apoptosis-related proteins, namely CD30 and FAIM3. We hypothesized that regulation of these genes by LCL161 may influence the drug's effects on T cells. We reversed the differential expression through genetic engineering and observed impaired costimulation by LCL161, particularly when CD30 was deleted. While LCL161 can provide a costimulatory signal to TAC T cells following exposure to isolated antigen, we did not observe a similar pattern when TAC T cells were stimulated with myeloma cells expressing the target antigen. We questioned whether FasL expression by myeloma cells may antagonize the costimulatory effects of LCL161. Fas-KO TAC T cells displayed superior expansion following antigen stimulation in the presence of LCL161, suggesting a role for Fas-related T cell death in limiting the magnitude of the T cell response to antigen in the presence of LCL161.

Conclusions

Our results demonstrate that LCL161 provides costimulation to TAC T cells exposed to antigen alone, however LCL161 did not enhance TAC T cell anti-tumor function when challenged with myeloma cells and may be limited due to sensitization of T cells towards Fas-mediated apoptosis.

Antibody Recognition of Cancer Cells via Glycan Surface Engineering

Stimulation of the body's immune system toward tumor cells is now well recognized as a promising strategy in cancer therapy. Just behind cell therapy and monoclonal antibodies, small molecule‐based strategies are receiving growing attention as alternatives to direct immune response against tumor cells. However, the development of small‐molecule approaches to modulate the balance between stimulatory immune factors and suppressive factors in a targeted way remains a challenge. Here, we report the cell surface functionalization of LS174T cancer cells with an abiotic hapten to recruit antibodies to the cell surface. Metabolic glycoengineering followed by covalent reaction with the hapten results in antibody recognition of the target cells. Microscopy and flow cytometry studies provide compelling evidence that metabolic glycoengineering and small molecule stimulators can be combined to direct antibody recognition.