TAK-164 is an
antibody-drug conjugate (ADC) comprising human anti-
guanylyl cyclase C (GCC)
monoclonal antibody conjugated to indolinobenzodiazepine
DNA alkylator IGN-P1 through a cleavable
alanine-
alanine dipeptide linker. TAK-164 is currently being evaluated for the treatment of
gastrointestinal cancers expressing GCC. The catabolism of TAK-164 was studied using 3H-labeled ADC using GCC-expressing HEK-293 (GCC-HEK-293) cells, rat tritosomes,
cathepsin B, and
tumor-bearing mice. Time- and target-dependent uptake of [3H]TAK-164 was observed in GCC-HEK-293 cells with approximately 12% of radioactivity associated with
DNA after 24 hours of incubation. Rat liver tritosomes and
cathepsin B yielded IGN-P1
aniline, sulfonated IGN-P1 (s-IGN-P1)
aniline, and a
lysine conjugate of IGN-P1 (IGN-P1-Lys)
aniline as catabolites. In
tumor-bearing mice, [3H]TAK-164 exhibited a terminal half-life of approximately 41 and 51 hours in plasma and blood, respectively, with low plasma clearance (0.75 ml/h per kilogram). The extractable radioactivity in plasma and
tumor samples revealed the presence of s-IGN-P1
aniline and IGN-P1
aniline as payload-related components. The use of a radiolabeled payload in the ADC in
tumor uptake investigations provided direct and quantitative evidence for
tumor uptake,
DNA binding, and proof of mechanism of action of the payload. SIGNIFICANCE STATEMENT: Since payload-related species are potent
cytotoxins, a thorough characterization of released products of ADCs, metabolites, and their drug interaction potential is necessary prior to clinical investigations. This study characterized in vitro and in vivo
DNA binding mechanisms and released products of TAK-164. The methodologies described here will be highly useful for characterization of payload-related products of ADCs in general.