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Antibody-drug conjugates (ADCs) are a class of biopharmaceutical drugs consisting of an antibody linked to a cytotoxic payload. The antibody binds specifically to the drug target, usually a biomolecule that is highly/specifically expressed on tumor cells, thus delivering the chemotherapeutic payload precisely to the target cancer cells and killing them.

The antibody and payload components of an ADC drug are linked by a "linker". The design of a suitable linker is critical to the stability, efficacy and payload profile of the ADC. CL2A is a cleavable complex PEG8 and triazole containing PABC peptide-mc linker that allows the release of the payload in an intracellular acidic environment. The linker is used in a number of ADCs in clinical trials, such as Gilead's labetuzumab (IMMU-130).

The cytotoxic payload is the warhead that destroys the cancer cells after internalization of the ADC. An ideal payload should have high potency, be stable under physiological conditions, and have functional groups available for conjugation with the antibody.

Monomethyl auristatin E (MMAE) is an inhibitor of tubulin polymerization. It is widely used in many ADCs including sofituzumab vedotin, polatuzumab vedotin, enfortumab vedotin, pinatuzumab vedotin, lifastuzumab vedotin, brentuximab vedotin, glembatumumab vedotin, etc. In these ADCs, vedotin refers to MMAE plus its linking structure to the antibody.

SN-38 (7-ethyl-10-hydroxycamptothecin) and DXd (exatecan derivatives) are both camptothecin derivatives and inhibitors of DNA topoisomerase I. They are proven payloads in approved ADC drugs such as sacituzumab govitecan and fam-trastuzumab deruxtecan.

SPEED Biosystems provides rabbit monoclonal antibodies against the ADC linker CL2A and the ADC payloads MMAE, SN38 and DXd. These antibodies have been extensively tested and are suitable for ELISA, immunoassay and PK/PD studies.