The recently developed compound, tetramethylthiocycloheptyne sulfoximine (TMTHSI), has shown to be a promising strained alkyne for strain-promoted azide–alkyne cycloaddition (SPAAC), metal-free click chemistry. This research explores the properties of TMTHSI-based compounds via three aspects: (1) large-scale production, (2) unique stability in acidic conditions and its subsequent use in peptide synthesis, and (3) the functionalization of antibodies. Here, it is shown that (1) scale-up is achieved on a scale of up to 100 g. (2) TMTHSI is remarkably stable against TFA allowing for the site-specific functionalization of peptides on resin. Finally, (3) the functionalization of an antibody with a model payload is very efficient, with antibody conjugation demonstrating more beneficial features such as a high yield and limited hydrophobicity as compared to other alkyne reagent conjugates. These results illustrate the high potential of TMTHSI for diverse bioconjugation applications, with production already being GMP-compatible and a highly efficient conversion resulting in attractive costs of goods.

Bioconjugate therapeutics comprise a fast-growing class of drugs with applications in various disease areas. In the past years, particularly antibody-drug conjugates (ADCs) have undergone a period of great success with eight products approved by the Food and Drug Administration (FDA) between 2019-2022 alone. The rapid emergence of novel bioconjugation technologies, payloads and linkers as well as their application on different protein modalities has made bioconjugate development and manufacturing increasingly complex. Clinical success of bioconjugates depends on the delicate interplay between the protein, linker and payload, which is often not readily predictable. Therefore, it is important to consider a range of different technologies when designing a bioconjugate drug. Since navigation of a constantly evolving technology landscape is challenging, it may be beneficial for many biotech companies to enter partnerships with a contract development and manufacturing organization (CDMO) that can help realize the drug concept by providing access to a range of tools for the development of bioconjugates. Partnering with a CDMO at an early-stage of drug development can greatly de-risk the program as the right CDMO can give guidance on how to design a conjugation process that not only fulfills the requirements in terms of product attributes but that is also robust enough to streamline further process development and upscale for moving towards an IND filing.