e13009 Background: Antibody based therapeutics have emerged as a highly promising treatment option for various forms of cancer. One such class of emergent antibody therapeutics is antibody-drug conjugates (ADCs), which has experienced remarkable success in the past few decades, including many candidates currently undergoing clinical trials. Despite its promise, developing effective ADCs remains a challenge due to extensive optimization with regard to antibody target identification, conjugate specificity, conjugation chemistry compatibility, heterogeneous side product co-purification, all affecting efficacy, PK/PD characteristics, and toxicity. There is a pressing need to develop alternative strategies for precise (site-specific), flexible (offering numerous options for conjugation site and chemistry), efficient, and scalable generation of antibody-drug conjugates to overcome these limitations and realize the full potential of this highly promising class of therapeutics. Methods: In this study, we demonstrate the feasibility of efficiently incorporating an azide-containing UAA into full-length antibody at different site and facilitate its site-specific functionalization, which provides a facile scale-up compatible route to generate precise antibody-drug conjugates with fine-tuned therapeutic properties. Specifically, we have engineered multiple variants of trastuzumab to contain the aforementioned UAA, enabling site-specific attachment of cytotoxic payloads, such as MMAE/MMAF, via click chemistry to generate ADCs with homogeneous DARs. Results: The resulting BrickBio ADCs exhibit high therapeutic efficacy against HER2+ cell lines in vitro as well as in mouse xenograft models. These homogenous ADCs additionally outperform traditional antibody conjugation technologies which lack site-specificity or site-selectivity. Conclusions: The ability to systematically vary the attachment topology between the drug and the antibody is a major strength of this approach and preliminary data suggest that such variation indeed affect ADC performance. BrickBio ADCs are currently in the preclinical stage with further efforts for safety studies underway.
Design and characterization of homogenous antibody-drug conjugates with a drug-to-antibody ratio of one prepared using an engineered antibody and a dual-maleimide pyrrolobenzodiazepine dimer