Site-specific conjugation methods can alleviate the complexities of manufacturing a heterogenousantibody-drug conjugate (ADC) product resulting from current random conjugation methods. At Eisai, we developed our REsidue-SPEcific Conjugation Technology (RESPECT®) to provide efficient conjugation methods to ensure homogeneous ADC products.
RESPECT®-H: Enzymatic conjugation on specific lysines
RESPECT®-H is an optimized, transglutaminase-based, site-specific conjugation method for attaching payloads onto specific lysine residues in the antibody. Glutamine-based linkers and payloads are efficiently conjugated to a lysine in CH1 through a stable isopeptide bond. RESPECT®-H requires just a single amino acid point mutation, avoiding multi-amino acid tags/substitutions or glycan modifications that can increase the risk of undesirable biophysical changes in the antibody or create potentially immunogenic epitopes.
Site-Specific Conjugation to Native and Engineered Lysines in Human Immunoglobulins by Microbial Transglutaminase. Bioconjug Chem. 2017. Sep 20;28(9):2471-2484.
RESPECT®-L: Thiol-based conjugation on an unpaired cysteine
Rabbit antibodies contain an additional intrachain disulfide bond between the Vκ and Cκ domains that is not present in any other species. Our scientists discovered that retaining the Vκ cysteine (Cys80) during humanization results in an unpaired cysteine that demonstrates high conjugation efficiency, low aggregate levels, retention of binding affinity, and low off-target cytotoxicity, all desirable properties for therapeutic ADCs.
Engineering humanized antibody framework sequences for optimal site-specific conjugation of cytotoxins. MAbs. 2017. Aug/Sep;9(6):907-915.
Generation of therapeutic immunoconjugates via Residue-Specific Conjugation Technology (RESPECT) utilizing a native cysteine in the light chain framework of Oryctolagus cuniculus. Cancer Biol Ther. 2017. May 4;18(5):347-357.
RESPECT®-H+L: 2 conjugation chemistries means dual payloads with 2 Mechanisms of Action (MOAs)
RESPECT®-L and RESPECT®-H conjugation methods rely on two very different chemistries; therefore, combining the two to make dual payload RESPECT®-H+L molecules is simple and straight-forward. Using this platform, an ADC can simultaneously deliver two different cytotoxins to the same cell, each with a differing MOA. RESPECT®-H+L also allows in vivo tracking of an ADC, whereby a cytotoxin is conjugated to one site and a tracking dye is attached to the other.
To learn more about RESPECT® and licensing opportunities, please call 1-877-327-5388 to speak with a member of our Business Development team.