Cutting-Edge Antibody Conjugates: Inspiring Innovation with AJICAP® Technology

Tomohiro Fujji, ADC Researcher at Ajinomoto, discussed the company’s cutting-edge AJICAP technology that uses site-specific conjugation and the stable linker. Ajinomoto offers comprehensive CDMO services across the globe, giving their clients the capacity and quality to scale up processes from clinical development to manufacturing. Fujii reiterated their mission: “Our services are designed to meet current and future demands of our client, ensuring the stable scale-up and seamless scale-up of their promising therapeutics.” AJICAP is an ADC manufacturing platform that maximises the function of the antibody and the payload in ADCs by relying on site-specific conjugation and stable linkers. Fujii highlighted that it is essential that the payload must not detach in the bloodstream or normal tissue, it must be released inside a cancer cell to be cytotoxic. While it seems contradictory to be stable and disconnect a stable conjugation site, AJICAP can achieve this balance. Traditional ADCs are synthesised through random conjugation, typically through lysine or cysteine chemistries. However, due to the heterogeneity of a resulting conjugate, traditional ADCs showed high toxicity and a low efficacy. To address these issues, site-specific conjugations are gaining traction in the ADC field. AJICAP conjugation is a next site-specific conjugation model. The technology is inspired by affinity peptides that have a strong binding affinity with the Fc portion of human IgGs. The binding sites were close to Lys248 and 288, so these peptides were modified to create a set of AJICAP reagents possessing the appropriate linker and the reactive group to form a covalent bond with Lys248 or 288. Fujji then outlined the mechanism of action. The AJICAP reagent binds to the Fc portion of human IgGs. Then via covalent bonds, the neighbouring lysine attacks the ester in the reagent to form this antibody peptide conjugate. The peptide is then cleaved and resulting orthogonal groups can react with various payloads. AJICAP conjugation technology enables precise control of the number of conjugations, resulting in ADCs with high efficacy and low toxicity. This technology is robust and simple, requiring only tangential flow filtration for purification. To take things a step further, Fujji developed a DAR1 conjugation technology that introduces single attachments, creating new possibilities for modality conjugates. Although there is only a single attachment, two affinity peptides in the reagent bind to both FC sites, allowing for the DAR1 conjugation through the reaction with lysine and the reactive group bound to the peptide. The traditional Val-Cit-PAB linker is commonly used as a cleavable linker but is susceptible to a wide variety of protein enzymes and is hydrophobic. So Fujji developed a new payload linker, the AJICAP linker to combat these issues. The linker is equipped with a hydrophilic peptide moiety and a cleavable peptide moiety. He explained that this improves the hydrophilicity of the resulting conjugate and offers protection from the various enzymatic attacks.  Comparative plasma stability studies demonstrated that the AJICAP linker-based ADCs showed promising stability compared to the other ADCs.  Another application of the AJICAP technology is multiple payload ADCs in cancer chemotherapy. AJICAP technology can prepare two types of multiple payload ADCs: DAR2+2 generated through the combination of AJICAP Lys248 and Lys288 chemistries, and DAR8+2 ADCs generated through the combination of reduction and AJICAP conjugation. DAR8+2 ADCs showed a better profile compared to DAR8 ADCs.