MAPN: First-in-Class Reagent for Kinetically Resolved Thiol-to-Thiol Conjugation

Area of Science:

• Bioconjugation Chemistry
• Medicinal Chemistry
• Biochemistry

Background:

• Thiols are critical functional groups in bioconjugation.
• Existing reagents enable thiol coupling to amines or carboxylic acids, but not thiol-to-thiol coupling.
• There is a need for specific reagents for creating heteroconjugates using two distinct thiols.

Purpose of the Study:

• To develop a novel reagent for kinetically resolved thiol-to-thiol coupling.
• To address the demand for advanced bioconjugation tools.
• To demonstrate the utility of the new reagent in preparing complex bioconjugates.

Main Methods:

• Development of p-(maleimide)-phenylpropionitrile (MAPN) as a heterobifunctional reagent.
• Comparative analysis of MAPN against p-phenylenedimaleimide for thiol-thiol coupling efficiency.
• Preparation of an antibody-drug conjugate (ADC) using MAPN for site-specific drug attachment.

Main Results:

• MAPN demonstrated superior performance in thiol-to-thiol heteroconjugate preparation compared to p-phenylenedimaleimide.
• MAPN enabled the first-time successful conjugation of mertansine (DM1) to the cysteine residues of Trastuzumab.
• The developed reagent offers kinetic resolution for selective thiol coupling.

Conclusions:

• MAPN is an efficient and advantageous reagent for kinetically resolved thiol-to-thiol bioconjugation.
• This new reagent expands the toolkit for creating complex heteroconjugates, particularly antibody-drug conjugates.
• The successful synthesis of a Trastuzumab-DM1 conjugate highlights MAPN's potential in drug development and targeted therapies.