Unraveling the Interaction between Carboxylesterase 1c and the Antibody-Drug Conjugate SYD985: Improved Translational
Ruud Ubink1, Eef H C Dirksen2, Myrthe Rouwette2
1Department of Preclinical, Synthon Biopharmaceuticals BV, Nijmegen, the Netherlands. ruud.ubink@synthon.com.
Abstract:
Carboxylesterase 1c (CES1c) is responsible for linker-drug instability and poor pharmacokinetics (PK) of several antibody-drug conjugates (ADC) in mice, but not in monkeys or humans. Preclinical development of these ADCs could be improved if the PK in mice would more closely resemble that of humans and is not affected by an enzyme that is irrelevant for humans. SYD985, a HER2-targeting ADC based on trastuzumab and linker-drug vc-seco-DUBA, is also sensitive to CES1c. In the present studies, we first focused on the interaction between CES1c and SYD985 by size- exclusion chromatography, Western blotting, and LC/MS-MS analysis, using recombinant CES1c and plasma samples. Intriguingly, CES1c activity not only results in release of the active toxin DUBA but also in formation of a covalent bond between CES1c and the linker of vc-seco-DUBA. Mass spectrometric studies enabled identification of the CES1c cleavage site on the linker-drug and the structure of the CES1c adduct. To assess the in vivo impact, CES1c-/- SCID mice were generated that showed stable PK for SYD985, comparable to that in monkeys and humans. Patient-derived xenograft (PDX) studies in these mice showed enhanced efficacy compared with PDX studies in CES1c+/+ mice and provided a more accurate prediction of clinical efficacy of SYD985, hence delivering better quality data. It seems reasonable to assume that CES1c-/- SCID mice can increase quality in ADC development much broader for all ADCs that carry linker-drugs susceptible to CES1c, without the need of chemically modifying the linker-drug to specifically increase PK in mice. Mol Cancer Ther; 17(11); 2389-98. ©2018 AACR.
Insights
Carboxylesterase 1c (CES1c) causes unstable antibody-drug conjugates (ADCs) in mice. CES1c-deficient mice show human-like pharmacokinetics and improved efficacy, enhancing ADC preclinical development.
Area of Science:
- Biochemistry
- Pharmacology
- Oncology
Background:
- Carboxylesterase 1c (CES1c) significantly impacts antibody-drug conjugate (ADC) pharmacokinetics (PK) in mice, leading to instability and poor drug exposure.
- This mouse-specific PK variability hinders accurate preclinical assessment of ADCs, including SYD985, a HER2-targeting ADC.
Purpose of the Study:
- To investigate the interaction between CES1c and the SYD985 ADC.
- To develop a mouse model that better reflects human PK for improved ADC preclinical development.
Main Methods:
- Size-exclusion chromatography, Western blotting, and LC/MS-MS analysis were used to study CES1c interaction with SYD985.
- CES1c-deficient (CES1c-/-) SCID mice were generated for in vivo PK and efficacy studies.
- Patient-derived xenograft (PDX) models were utilized to compare efficacy in CES1c-/- versus CES1c+/+ mice.
Main Results:
- CES1c cleaves the linker-drug of SYD985, releasing the active toxin and forming a covalent adduct with CES1c.
- CES1c-/- mice exhibited stable SYD985 PK, mirroring human and monkey profiles.
- Enhanced SYD985 efficacy and more accurate clinical efficacy predictions were observed in PDX studies using CES1c-/- mice.
Conclusions:
- CES1c significantly affects ADC PK and efficacy in mice.
- CES1c-/- SCID mice provide a more predictive preclinical model for ADC development.
- This approach improves ADC preclinical quality without requiring linker-drug modification.
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