DM-002 (Xadcera Biopharma)

Dendrimers are branched macromolecular structures that are useful nanocarriers for small-molecule drugs, such as cancer therapeutics. Their small size permits penetration into solid tumors, coupled with functionalization with a low-fouling PEG coating that minimizes transient cellular interactions and enhances plasma circulation time. While PEGylated dendrimers show significant promise as anticancer therapeutics, there is potential to increase tumor cell specificity and drive uptake of drugs into cells by conjugating cell-targeting ligands onto the dendrimers. To achieve this, we used an expanded genetic code and bio-orthogonal click chemistry to functionalize monomethyl auristatin E (MMAE)-loaded PEGylated dendrimers with a single tumor cell-targeting nanobody per dendrimer. The uniform addition of a single nanobody ligand facilitated greater intracellular uptake of the drug payload into HER2-positive target cells, while preserving the desirable circulatory characteristics of dendrimers. While the nanobody-dendrimer conjugates show similar levels of tumor infiltration over 24 h compared to unmodified dendrimers, the targeted dendrimers had significantly greater inhibition of tumor growth and long-term retention in the tumors. Our results highlight that biodistribution studies alone are poor predictors of therapeutic performance. The controlled conjugation strategy presented here preserves the size advantage and tissue penetration of dendrimers while maximizing targeted cellular uptake and potency in difficult-to-access solid tumor tissue.

Targeted payload delivery strategies, such as antibody‐drug conjugates (ADCs), have emerged as important therapeutics. Although considerable efforts have been made in the areas of antibody engineering and labeling methodology, improving the overall physicochemical properties of the linker/payload combination remains an important challenge. Here we report an approach to create an intrinsically hydrophilic linker domain. We find that benzyl α‐ammonium carbamates (BACs) undergo tandem 1,6–1,2‐elimination to release secondary amines. Using a fluorogenic hemicyanine as a model payload component, we show that a zwitterionic BAC linker improves labeling efficiency and reduces antibody aggregation when compared to a commonly used para‐amino benzyl (PAB) linker as well as a cationic BAC. Cellular and in vivo fluorescence imaging studies demonstrate that the model payload is specifically released in antigen‐expressing cells and tumors. The therapeutic potential of the BAC linker strategy was assessed using an MMAE payload, a potent microtubule‐disrupting agent frequently used for ADC applications. The BAC‐MMAE combination enhances labeling efficiency and cellular toxicity when compared to the routinely used PAB‐Val‐Cit ADC analogue. Broadly, this strategy provides a general approach to mask payload hydrophobicity and improve the properties of targeted agents.