Tyrosine kinase chimeras for antigen-selective T-body therapy

Targeting T cells with bispecific antibodies for cancer therapy

Bispecific antibodies (BiAbs) offer a unique opportunity to redirect immune effector cells to kill cancer cells. BiAbs combine the benefits of different binding specificities of two monoclonal antibodies (mAbs) into a single construct. This unique feature of BiAbs enables approaches that are not possible with single mAbs. Advances in antibody engineering and antigen profiling of malignant cells have led to the development of a number of BiAb formats and their combinations for redirecting effector cells to tumor targets. There have been significant advances in the design and application of BiAbs for intravenous and local injection.The initial barrier of cytokine storm has been partially overcome by more recent constructs that have improved clinical effectiveness without dose-limiting toxicities. Since the recent revival of BiAbs, there has been multiple, ongoing, phase I/II and III trials, and some promising clinical outcomes have been reported in completed clinical studies. This review focuses on arming T cells with BiAbs to create the 'poor man's cytotoxic lymphocyte'.

Retargeting T cells and immune effector cells with bispecific antibodies

The development of BiAbs for therapeutic applications in cancer shows promise. As our understanding of effector cell receptor biology for triggering of cytotoxic functions improves and the behavior of TAA and the targeting antibody engagement is elucidated, customized BiAb reagents can be engineered to optimize in vivo or ex vivo arming of T cells for targeting tumors. Additionally, other variables that require consideration in the equation for successful T cell immunotherapy include: the type of effector cells, their state of activation, the type of effector receptor being activated or tareeted. the presence of Tregs, the affinity of the anti-effector cell antibody and the anti-TAA antibody, the type of BiAb (mouse, humanized, or human), the number of binding sites for the T cells or TAA, the presence or absence of decoy antigen, whether the TAA modulates after being engaged by antibody, the type of tumor, the tumor burden, and last, but not least, the amount of 'immunologic' space available for the adoptively transferred cells to expand and function.

Anti-idiotypic antibody facilitates scFv chimeric immune receptor gene transduction and clonal expansion of human lymphocytes for tumor therapy

Chimeric immune receptors (CIR) transduced into lymphocytes link target recognition by single chain antibody Fv (scFv) to activation through CD28/TCRzeta signaling. As surrogate antigens, anti-idiotypic antibodies may facilitate gene-transduction and clonal expansion of human lymphocytes for in vivo tumor therapy. The murine monoclonal antibody (MAb) 8H9 reacts with a novel antigen widely expressed on solid tumors. A CIR consisting of human CD8-leader sequence, 8H9-scFv, CD28 (transmembrane and cytoplasmic domains), and TCR-zeta chain was constructed, ligated into the pMSCVneo vector, and used to transfect the packaging line GP + envAM12 bearing an amphotropic envelope. Rat anti-idiotypic MAb 2E9 (IgG2a) was used to clone retroviral producer line as well as to expand gene-modified primary human lymphocytes. Sequential enrichments using either affinity chromatography or cell sorting using anti-idiotypic MAb 2E9 significantly improved the percentage of producer clones positive for surface 8H9-scFv and the efficiency of their supernatant in transducing the indicator cell line K562. By 3 weeks of in vitro culture, >95% of transduced primary human lymphocytes were CIR-positive. Upon periodic stimulation with 2E9, these lymphocytes underwent >10(6)-fold expansion by 6 months in culture. They mediated antigen-specific non-MHC restricted cytokine release and tumor cytotoxicity, and inhibited human xenograft engraftment in SCID mice. Anti-idiotypic antibody may provide a useful tool for optimizing gene transduction of CIR fusion constructs into primary human lymphocytes and their continual expansion in vitro.

The use of phage display for the development of tumour targeting agents

One way to improve the selectivity of therapeutic molecules in clinical oncology would be to target them on the tumour site, thereby sparing normal tissues. The development of targeted therapeutic methodologies relies in most cases on the availability of binding molecules specific for tumour-associated markers. The display of repertoires of polypeptides on the surface of filamentous phage, together with the efficient selection-amplification of the desired binding specificities using affinity capture, represents an efficient route towards the isolation of specific peptides and proteins that could act as vehicles for tumour targeting applications. Most investigations in this area of research have so far been performed with phage derived recombinant antibodies, which have been shown to selectively target tumour-associated markers both in preclinical animal models and in the clinic. However, future developments with other classes of polypeptides (small constrained peptides, small globular proteins) promise to be important for the selective delivery of therapeutic agents to the tumour site.