The term bispecific antibody (bsAb) is used to describe a large family of molecules designed to recognize two different epitopes or antigens. BsAbs come in many formats, ranging from relatively small proteins, merely consisting of two linked antigen-binding fragments, to large immunoglobulin G (IgG)-like molecules with additional domains attached. An attractive bsAb feature is their potential for novel functionalities - that is, activities that do not exist in mixtures of the parental or reference antibodies. In these so-called obligate bsAbs, the physical linkage of the two binding specificities creates a dependency that can be temporal, with binding events occurring sequentially, or spatial, with binding events occurring simultaneously, such as in linking an effector to a target cell. To date, more than 20 different commercialized technology platforms are available for bsAb creation and development, 2 bsAbs are marketed and over 85 are in clinical development. Here, we review the current bsAb landscape from a mechanistic perspective, including a comprehensive overview of the pipeline.

Bispecific antibodies: a mechanistic review of the pipeline.

MAGE A3, which belongs to the family of cancer-testis antigens, is an attractive target for adoptive therapy given its reactivation in various tumors and limited expression in normal tissues. We developed an affinity-enhanced T cell receptor (TCR) directed to a human leukocyte antigen (HLA)–A*01–restricted MAGE A3 antigen (EVDPIGHLY) for use in adoptive therapy. Extensive preclinical investigations revealed no off-target antigen recognition concerns; nonetheless, administration to patients of T cells expressing the affinity-enhanced MAGE A3 TCR resulted in a serious adverse event (SAE) and fatal toxicity against cardiac tissue. We present a description of the preclinical in vitro functional analysis of the MAGE A3 TCR, which failed to reveal any evidence of off-target activity, and a full analysis of the post-SAE in vitro investigations, which reveal cross-recognition of an off-target peptide. Using an amino acid scanning approach, a peptide from the muscle protein Titin (ESDPIVAQY) was identified as an alternative target for the MAGE A3 TCR and the most likely cause of in vivo toxicity. These results demonstrate that affinity-enhanced TCRs have considerable effector functions in vivo and highlight the potential safety concerns for TCR-engineered T cells. Strategies such as peptide scanning and the use of more complex cell cultures are recommended in preclinical studies to mitigate the risk of off-target toxicity in future clinical investigations.

https://www.researchgate.net/profile/Kannan_Vivekanandan/publication/255707362_Identification_of_a_Titin-Derived_HLA-A1-Presented_Peptide_as_a_Cross-Reactive_Target_for_Engineered_MAGE_A3-Directed_T_Cells/links/54fedb400cf2672e224088ed.pdf

Identification of a Titin-derived HLA-A1-presented peptide as a cross-reactive target for engineered MAGE A3-directed T cells

Fifty years since the first description of an association between HLA and human disease, HLA molecules have proven to be central to physiology, protective immunity and deleterious, disease-causing autoimmune reactivity. Technological advances have enabled pivotal progress in the determination of the molecular mechanisms that underpin the association between HLA genetics and functional outcome. Here, we review our current understanding of HLA molecules as the fundamental platform for immune surveillance and responsiveness in health and disease. We evaluate the scope for personalized antigen-specific disease prevention, whereby harnessing HLA–ligand interactions for clinical benefit is becoming a realistic prospect.

HLA variation and disease

Clonal selection theory proposed that individual T cells are specific for a single peptide–MHC antigen. However, the repertoire of αβ T cell receptors (TCRs) is dwarfed by the vast array of potential foreign peptide–MHC complexes, and a comprehensive system requires each T cell to recognize numerous peptides and thus be cross-reactive. This compromise on specificity has profound implications because the chance of any natural peptide–MHC ligand being an optimal fit for its cognate TCR is small, as there will almost always be more-potent agonists. Furthermore, any TCR raised against a specific peptide–MHC complex in vivo can only be the best available solution from the naive T cell pool and is unlikely to be the best possible solution from the substantially greater number of TCRs that could theoretically be produced. This 'systems view' of TCR recognition provides a plausible cause for autoimmune disease and substantial scope for multiple therapeutic interventions.

/pdf/why-must-t-cells-be-cross-reactive-4lbq73eufs.pdf

Why must T cells be cross-reactive?

Th17 cells play a complex and controversial role in tumor immunity and have been found to exhibit a fluctuating identity within the context of cancer. The recent, expanding literature on these cells attests to their puzzling nature, either promoting or suppressing tumor growth depending on the malignancy and course of therapeutic intervention investigated. This review addresses several newly appreciated factors that may help delineate Th17 cells’ immunological properties in the context of cancer. Several reports suggest that inflammatory signals induced in the tumor milieu regulate the functional fate and antitumor activity of Th17 cells. Recent findings also point to significant alterations in Th17 cells due to their interplay with regulatory T lymphocytes and cytotoxic CD8+ T cells within the tumor microenvironment. Finally, an appreciation for the stem cell-like properties of Th17 cells that augment their persistence and activity emerges from recent reports. The impact of these factors on Th17 cells’ antitumor efficacy and how these factors may be exploited to improve cancer therapies will be discussed.

/pdf/th17-cells-in-cancer-the-ultimate-identity-crisis-2p7b4srd5l.pdf

Th17 Cells in Cancer: The Ultimate Identity Crisis

T cell immunity can potentially eradicate malignant cells and lead to clinical remission in a minority of patients with cancer. In the majority of these individuals, however, there is a failure of the specific T cell receptor (TCR)–mediated immune recognition and activation process. Here we describe the engineering and characterization of new reagents termed immune-mobilizing monoclonal TCRs against cancer (ImmTACs). Four such ImmTACs, each comprising a distinct tumor-associated epitope-specific monoclonal TCR with picomolar affinity fused to a humanized cluster of differentiation 3 (CD3)-specific single-chain antibody fragment (scFv), effectively redirected T cells to kill cancer cells expressing extremely low surface epitope densities. Furthermore, these reagents potently suppressed tumor growth in vivo. Thus, ImmTACs overcome immune tolerance to cancer and represent a new approach to tumor immunotherapy.

Monoclonal TCR-redirected tumor cell killing

A T cell receptor (TCR) having the property of binding to EVDPIGHLY HLA-A1 complex and comprising a specified wild type TCR which has specific mutations in the TCR alpha variable domain and/or the TCR beta variable domain to increase affinity. Such TCRs are useful for adoptive therapy.

T cell receptors

Monoclonal TCR-redirected tumor cell killing. Nat Med

A T cell receptor (TCR) having the property of binding to the gp100 YLEPGPVTA peptide-HLA-A2 complex and comprising a TCR alpha variable domain and/or a TCR beta variable domain, characterized in that the domains are mutated relative to a TCR having the extracellular alpha and beta chain sequences SEQ ID NOs: 2 and that the TCR has a binding affinity for, and/or a binding half-life for, the YLEPGPVTA-HLA-A2 complex at least double that of a reference TCR. Embodiments of the invention such as the use of such TCRs in adoptive therapy, and fusions of such TCRs with therapeutic agents are also described.

Non-naturally occurring T cell receptors

La presente invention a pour objet un recepteur des lymphocytes T (TCR) ayant la propriete de se lier au complexe HLA-A2 peptide gp100 YLEPGPVTA et comprenant un domaine variable alpha du TCR et/ou un domaine variable beta du TCR, caracterise en ce que : (i) ledit TCR est mute par rapport a un TCR ayant les sequences de chaine extracellulaires alpha et beta SEQ ID Nos: 2 et 3 au niveau de ses acides amines 1 a 109 du domaine variable de la chaine alpha de SEQ ID No: 2 et/ou de ses acides amines 1 a 112 du domaine variable de la chaine beta de SEQ ID No: 3; et (ii) ledit domaine variable alpha possede au moins une identite de sequence de 90 % par rapport a la sequence d'acides amines 1 a 109 de SEQ ID No: 2, et/ou ledit domaine variable beta possede au moins une identite de sequence de 90 % par rapport a la sequence d'acides amines 1 a 112 de SEQ ID No: 3; et (iii) ledit TCR possede une affinite de liaison pour, et/ou une demi-vie de liaison pour le complexe YLEPGPVTA-HLA-A2 au moins egale au double de celle d'un TCR de reference, ledit TCR de reference ayant la sequence de chaine extracellulaire alpha SEQ ID No: 45 et la sequence de chaine extracellulaire beta SEQ ID No: 46 La presente invention concerne egalement l'utilisation de tels TCR en therapie adoptive, et des fusions de tels TCR avec des agents therapeutiques

Naomi Harwood

Papers

Monoclonal TCR-redirected tumor cell killing

T cell receptors

Monoclonal TCR-redirected tumor cell killing. Nat Med

Non-naturally occurring T cell receptors

Récepteurs des lymphocytes t