Improving the targeting of therapeutics with single-domain antibodies.

INTRODUCTION: The targeted delivery of therapeutic agents greatly increases their effectiveness while simultaneously reducing negative side effects. In the past, targeting of therapeutics has been accomplished with nucleic acids, peptides/proteins, and conventional antibodies. A promising alternative to the conventional antibodies often used in therapeutic targeting are significantly smaller-sized antibody fragments known as single-domain antibodies (sdAbs). AREAS COVERED: Recent advances in the utility of sdAbs for targeting of therapeutic agents along with relevant examples from the literature are discussed. Their advantages when compared to other targeting strategies as well as their challenges and limitations is also covered. EXPERT OPINION: The development of sdAb-based targeted therapeutics will likely continue. The identification of novel protein modification techniques will provide more options for sdAb modification (conjugation, immobilization, functionalization), allowing a wider array of therapeutic agents to be successfully targeted and delivered using sdAbs. This will also spur the selection of sdAbs with specificity for other targets having relevance towards therapeutics.