Light-inducible T cell engagers trigger, tune, and shape the activation of primary T cells

To mount appropriate responses, T cells integrate complex sequences of receptor stimuli perceived during transient interactions with antigen-presenting cells. Although it has been hypothesized that the dynamics of these interactions influence the outcome of T cell activation, methodological limitations have hindered its formal demonstration. Here, we have engineered the Light-inducible T cell engager (LiTE) system, a recombinant optogenetics-based molecular tool targeting the T cell receptor (TCR). The LiTE system constitutes a reversible molecular switch displaying exquisite reactivity. As proof of concept, we dissect how specific temporal patterns of TCR stimulation shape T cell activation. We established that CD4+ T cells respond to intermittent TCR stimulation more efficiently than their CD8+ T cells counterparts and provide evidence that distinct sequences of TCR stimulation encode different cytokine programs. Finally, we show that the LiTE system could be exploited to create light-activated bispecific T cell engagers and manipulate tumor cell killing. Overall, the LiTE system provides opportunities to understand how T cells integrate TCR stimulations and to trigger T cell cytotoxicity with high spatiotemporal control.

Cytokine release syndrome and cancer immunotherapies - historical challenges and promising futures

Cancer is the leading cause of death worldwide. Cancer immunotherapy involves reinvigorating the patient's own immune system to fight against cancer. While novel approaches like Chimeric Antigen Receptor (CAR) T cells, bispecific T cell engagers, and immune checkpoint inhibitors have shown promising efficacy, Cytokine Release Syndrome (CRS) is a serious adverse effect and remains a major concern. CRS is a phenomenon of immune hyperactivation that results in excessive cytokine secretion, and if left unchecked, it may lead to multi-organ failure and death. Here we review the pathophysiology of CRS, its occurrence and management in the context of cancer immunotherapy, and the screening approaches that can be used to assess CRS and de-risk drug discovery earlier in the clinical setting with more predictive pre-clinical data. Furthermore, the review also sheds light on the potential immunotherapeutic approaches that can be used to overcome CRS associated with T cell activation.

Leveraging IFNγ/CD38 regulation to unmask and target leukemia stem cells in acute myelogenous leukemia

Elimination of drug-resistant leukemia stem cells (LSCs) represents a major challenge to achieve a cure in acute myeloid leukemia (AML). Although AML blasts generally retain high levels of surface CD38 (CD38pos), the presence of CD34 and lack of CD38 expression (CD34posCD38neg) are immunophenotypic features of both LSC-enriched AML blasts and normal hematopoietic stem cells (HSCs). We report that IFN-γ induces CD38 upregulation in LSC-enriched CD34posCD38neg AML blasts, but not in CD34posCD38neg HSCs. To leverage the IFN-γ mediated CD38 up-regulation in LSCs for clinical application, we created a compact, single-chain CD38-CD3-T cell engager (CD38-BIONIC) able to direct T cells against CD38pos blasts. Activated CD4pos and CD8pos T cells not only kill AML blasts but also produce IFNγ, which leads to CD38 expression on CD34posCD38neg LSC-enriched blasts. These cells then become CD38-BIONIC targets. The net result is an immune-mediated killing of both CD38neg and CD38pos AML blasts, which culminates in LSC depletion.

Bispecific T cell engagers kill resistant cells during KRAS-G12C blockade therapy

The covalent KRAS-G12C inhibitors (G12Ci) are rapidly changing the treatment landscape for advanced non-small cell lung cancer, but drug resistance remains a clinical challenge. Two recent studies have developed bispecific T cell engagers that form a link between T cells and tumor cells to selectively eliminate G12Ci-resistant cells.

CD19-Targeted Immunotherapies for Diffuse Large B-Cell Lymphoma

Surgical resection, chemotherapy and radiotherapy were, for many years, the only available cancer treatments. Recently, the use of immune checkpoint inhibitors and adoptive cell therapies has emerged as promising alternative. These cancer immunotherapies are aimed to support or harness the patient's immune system to recognize and destroy cancer cells. Preclinical and clinical studies, based on the use of T cells and more recently NK cells genetically modified with chimeric antigen receptors retargeting the adoptive cell therapy towards tumor cells, have already shown remarkable results. In this review, we outline the latest highlights and progress in immunotherapies for the treatment of Diffuse Large B-cell Lymphoma (DLBCL) patients, focusing on CD19-targeted immunotherapies. We also discuss current clinical trials and opportunities of using immunotherapies to treat DLBCL patients.

Neural stem cells secreting bispecific T cell engager to induce selective antiglioma activity

Glioblastoma (GBM) is the most lethal primary brain tumor in adults. No treatment provides durable relief for the vast majority of GBM patients. In this study, we've tested a bispecific antibody comprised of single-chain variable fragments (scFvs) against T cell CD3ε and GBM cell interleukin 13 receptor alpha 2 (IL13Rα2). We demonstrate that this bispecific T cell engager (BiTE) (BiTE^LLON) engages peripheral and tumor-infiltrating lymphocytes harvested from patients' tumors and, in so doing, exerts anti-GBM activity ex vivo. The interaction of BiTE^LLON with T cells and IL13Rα2-expressing GBM cells stimulates T cell proliferation and the production of proinflammatory cytokines interferon γ (IFNγ) and tumor necrosis factor α (TNFα). We have modified neural stem cells (NSCs) to produce and secrete the BiTE^LLON (NSC^LLON). When injected intracranially in mice with a brain tumor, NSC^LLON show tropism for tumor, secrete BiTE^LLON, and remain viable for over 7 d. When injected directly into the tumor, NSC^LLON provide a significant survival benefit to mice bearing various IL13Rα2⁺ GBMs. Our results support further investigation and development of this therapeutic for clinical translation.

Soluble Expression of Fc-Fused T Cell Receptors Allows Yielding Novel Bispecific T Cell Engagers

The specific recognition of T cell receptors (TCR) and peptides presented by human leukocyte antigens (pHLAs) is the core step for T cell triggering to execute anti-tumor activity. However, TCR assembly and soluble expression are challenging, which precludes the broad use of TCR in tumor therapy. Herein, we used heterodimeric Fc to assist in the correct assembly of TCRs to achieve the stable and soluble expression of several TCRs in mammalian cells, and the soluble TCRs enable us to yield novel bispecific T cell engagers (TCR/aCD3) through pairing them with an anti-CD3 antibody. The NY-ESO-1/LAGE-1 targeted TCR/aCD3 (NY-TCR/aCD3) that we generated can redirect naïve T cells to specific lysis antigen-positive tumor cells, but the potency of the NY-TCR/aCD3 was disappointing. Furthermore, we found that the activation of T cells by NY-TCR/aCD3 was mild and unabiding, and the activity of NY-TCR/aCD3 could be significantly improved when we replaced naïve T cells with pre-activated T cells. Therefore, we employed the robust T cell activation ability of staphylococcal enterotoxin C2 (SEC2) to optimize the activity of NY-TCR/aCD3. Moreover, we found that the secretions of SEC2-activated T cells can promote HLA-I expression and thus increase target levels, which may further contribute to improving the activity of NY-TCR/aCD3. Our study described novel strategies for soluble TCR expression, and the optimization of the generation and potency of TCR/aCD3 provided a representative for us to fully exploit TCRs for the precision targeting of cancers.

Bispecific T Cell Engagers for the Treatment of Multiple Myeloma: Achievements and Challenges

MM is the second most common hematological malignancy and represents approximately 20% of deaths from hematopoietic cancers. The advent of novel agents has changed the therapeutic landscape of MM treatment; however, MM remains incurable. T cell-based immunotherapy such as BTCEs is a promising modality for the treatment of MM. This review article discusses the advancements and future directions of BTCE treatments for MM.

Solid Tumor Immunotherapy with T Cell Engager-Armed Oncolytic Viruses

Oncolytic viruses (OVs) are novel anticancer agents that combine direct cancer cell killing with the stimulation of antitumor immunity. In addition, OVs can be engineered to deliver biological therapeutics directly to tumors, offering unique opportunities to design multimodal anticancer strategies. Here, a case for arming OVs with bispecific T cell engagers (BiTEs) is put forward. BiTEs redirect the cytotoxicity of polyclonal T cells to target cells of choice, and have demonstrated efficacy against a number of hematological cancers. However, the success of BiTEs in the treatment of solid tumors appears more limited, at least in part due to: (i) poor delivery kinetics and penetration into tumors, and (ii) on-target off-tumor activity, leading to dose-limiting toxicities. Linking the production of BiTEs to OV replication provides an exciting means to restrict production to the tumor site, widen their therapeutic window, and synergize with direct oncolysis. This review summarizes progress thus far in the preclinical development of BiTE-armed OVs, and explores the possibility of cotargeting cancer cells and nontransformed stromal cells.