Fragment-Based Immune Cell Engager Antibodies in Treatment of Cancer, Infectious and Autoimmune Diseases: Lessons and Insights from Clinical and Translational Studies.

Since the advent of recombinant DNA technologies and leading up to the clinical approval of T cell engager blinatumomab, the modular design of therapeutic antibodies has enabled the fusion of antibody fragments with proteins of various functionalities. This has resulted in an expansive array of possible mechanisms of action and has given birth to fragment-based antibodies (fbAbs) with immune cell engager modalities. In searchable databases, the preclinical development of these antibodies has shown promise; however, clinical outcomes and restructuring efforts involving these agents have produced mixed results and uncertainties. Amid budgetary cuts in both academia and industry, critical planning and evaluation of drug R&D would be more essential than ever before. While many reviews have provided outstanding summaries of preclinical phase fbAbs and cataloged relevant clinical trials, to date, very few of the articles in searchable databases have comprehensively reviewed the details of clinical outcomes along with the underlying reasons or potential explanations for the success and failures of these fbAb drug products. To fill the gap, in this review, we seek to provide the readers with clinically driven insights, accompanied by translational and mechanistic studies, on the current landscape of fragment-based immune cell engager antibodies in treating cancer, infectious, and autoimmune diseases.