Research Progress of Small-Format Antibody Drug Conjugates and Analogs

In cancer treatment, the effectiveness of solid tumor treatment has always been a concern in the pharmaceutical industry. Antibodies and antibody-drug conjugates have been clinically used to treat some solid tumors, but their large molecular weights cause limited penetration and thus cannot fully exert the expected efficacy. And because it circulates for a long time in vivo, it can cause toxicity to the liver and other tissues, limit the therapeutic window. Small-format drug conjugates and their analogs, such as antibody fragment drug conjugates, scaffold antibody-drug conjugates, or peptide drug conjugates, can quickly penetrate the tumor and accumulate in the tumor tissue. Compared with traditional antibodydrug conjugates, the renal metabolism rate of small-format drug conjugates increased, enabling rapid metabolism of free drugs in plasma and reducing adverse reactions caused by long-term systemic circulation of drugs. However, its short half-life may reduce the actual amount of drug entering the tumor. Therefore, different half-life extension methods have been derived to adjust the drug half-life, increase the total amount entering the tumor tissue, and improve the therapeutic effect. This review summarizes the preclinical and clinical progress of small-format drug conjugates and their development trend to provide some reference for the development of small-format drug conjugates and their analogs.