Antibody-drug conjugates (ADCs) are a growing class of targeted therapeutics. ADC conjugation strategies remain a challenge, because conventional chemical conjugation methods can produce undesirable heterogeneous products with variable drug-to-antibody ratios (DAR) that limit consistency and performance. To address these challenges, researchers developed a modular strategy using de novo designed Ecoil/Kcoil coiled-coil heterodimers, which conjugate antibodies and payloads in a noncovalent, site-specific manner. By engineering trastuzumab (TZM) with Ecoil sequences, homogeneous conjugates with an ideal DAR of 4 could be generated that still preserve antibody targeting functionality.
In a 2025 Bioconjugate Chemistry study, Baniahmad et al. evaluated the Ecoil/Kcoil strategy using payloads linked to Kcoil peptides. Biotium’s CF®750 dye was utilized for multiple purposes. Kcoil peptides were conjugated to Biotium’s CF®750 maleimide and paired with Ecoil-tagged TZM to form TZM-E/K-CF750 complexes. TZM labeled with direct NHS-ester CF®750 Dye was used as the control for conventional ADC.
Using near-infrared CF®750 allowed researchers to track biodistribution in vivo. They found that the coiled-coil conjugate (TZM-E/K-CF750) achieved tumor-specific accumulation and retention compared to the E5/K5-CF750 negative control. The coiled-coil conjugate remained stable in serum and successfully localized to HER2-positive tumors in mouse models, with signals lasting up to 10 days after injection.
These results validate CF®750 as a reliable near-infrared probe for in vivo imaging, showing how it may be used for evaluating novel antibody conjugation methods. Overall, these results underscore the promise of scalable coiled-coil assemblies for creating more uniform and modular ADCs.
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