Harnessing single-domain antibodies for CAR-T and bispecific antibody development

Emerging antibody-based therapeutic modalities such as CAR-Ts and bispecific antibodies have proven highly efficacious in treating diseases, including hematological malignancies. However, the complex molecular architectures of these novel agents present significant challenges in their design and production, for which binding moieties with small size and favorable physicochemical properties may offer a promising solution. Single domain antibodies (sdAbs), typically derived from the heavy chain antibodies of camelids and cartilaginous fishes but increasingly from synthetic and other sources as well, are small (12-15 kDa), well expressed, and exhibit favorable physicochemical properties, making them ideal targeting domains for these new modalities. In this article, we review the origins and characteristics of sdAbs, along with recent studies on CAR-T cell therapies and bispecific antibodies for hematological malignancies that incorporate sdAbs into their constructs, with emphasis on their structures, binding properties, and therapeutic efficacies. Together, these developments underscore the promise of sdAb-based CAR-Ts and bispecific antibodies as next-generation therapeutics, with the potential to expand treatment options and improve outcomes in hematological malignancies and beyond.