title: Drug-to-antibody determination for an antibody-drug-conjugate utilizing cathepsin B digestion coupled with reversed-phase high-pressure liquid chromatography analysis.
abstract: Antibody drug conjugates or ADCs are currently being evaluated for their effectiveness as targeted chemotherapeutic agents across the pharmaceutical industry. Due to the complexity arising from the choice of antibody, drug and linker; analytical methods for release and stability testing are required to provide a detailed understanding of both the antibody and the drug during manufacturing and storage. The ADC analyzed in this work consists of a tubulysin drug analogue that is randomly conjugated to lysine residues in a human IgG1 antibody. The drug is attached to the lysine residue through a peptidic, hydrolytically stable, cathepsin B cleavable linker. The random lysine conjugation produces a heterogeneous mixture of conjugated species with a variable drug-to-antibody ratio (DAR), therefore, the average amount of drug attached to the antibody is a critical parameter that needs to be monitored. In this work we have developed a universal method for determining DAR in ADCs that employ a cathepsin B cleavable linker. The ADC is first cleaved at the hinge region and then mildly reduced prior to treatment with the cathepsin B enzyme to release the drug from the antibody fragments. This pre-treatment allows the cathepsin B enzyme unrestricted access to the cleavage sites and ensures optimal conditions for the cathepsin B to cleave all the drug from the ADC molecule. The cleaved drug is then separated from the protein components by reversed phase high performance liquid chromatography (RP-HPLC) and quantitated using UV absorbance. This method affords superior cleavage efficiency to other methods that only employ a cathepsin digestion step as confirmed by mass spectrometry analysis. This method was shown to be accurate and precise for the quantitation of the DAR for two different random lysine conjugated ADC molecules.
authors.affiliation: Bristol-Myers Squibb, 519 Route 173, Bloomsbury, NJ 08551, United States. Electronic address: michael.adamo@bms.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Adamo
authors.affiliation: Bristol-Myers Squibb, 519 Route 173, Bloomsbury, NJ 08551, United States.
authors.forename: Guoyong
authors.initials: G
authors.lastname: Sun
authors.affiliation: Bristol-Myers Squibb, 1 Squibb Dr., New Brunswick, NJ 08901, United States.
authors.forename: Difei
authors.initials: D
authors.lastname: Qiu
authors.affiliation: Bristol-Myers Squibb, 1 Squibb Dr., New Brunswick, NJ 08901, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Valente
authors.affiliation: Bristol-Myers Squibb, 1 Squibb Dr., New Brunswick, NJ 08901, United States.
authors.forename: Wenkui
authors.initials: W
authors.lastname: Lan
authors.affiliation: Bristol-Myers Squibb, 519 Route 173, Bloomsbury, NJ 08551, United States.
authors.forename: Hangtian
authors.initials: H
authors.lastname: Song
authors.affiliation: Bristol-Myers Squibb, 1 Squibb Dr., New Brunswick, NJ 08901, United States.
authors.forename: Mark
authors.initials: M
authors.lastname: Bolgar
authors.affiliation: Bristol-Myers Squibb, 519 Route 173, Bloomsbury, NJ 08551, United States.
authors.forename: Amit
authors.initials: A
authors.lastname: Katiyar
authors.affiliation: Bristol-Myers Squibb, 519 Route 173, Bloomsbury, NJ 08551, United States.
authors.forename: Girija
authors.initials: G
authors.lastname: Krishnamurthy
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry; D002021:Buffers; D002401:Cathepsin B / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D006801:Humans; D018796:Immunoconjugates / Q000737:chemistry*; D007074:Immunoglobulin G / Q000032:analysis*; D008239:Lysine / Q000737:chemistry; D013058:Mass Spectrometry; D004364:Pharmaceutical Preparations / Q000032:analysis* / Q000737:chemistry; D011136:Polysorbates / Q000737:chemistry; D012015:Reference Standards; D015203:Reproducibility of Results; D014466:Ultraviolet Rays
chemical_list: D000970:Antineoplastic Agents; D002021:Buffers; D018796:Immunoconjugates; D007074:Immunoglobulin G; D004364:Pharmaceutical Preparations; D011136:Polysorbates; D002401:Cathepsin B; D008239:Lysine
keywords: ADC; Antibody drug conjugate; Cathepsin B; DAR; Drug to antibody ratio