Branched pegylated linker-auristatin to control hydrophobicity for the production of homogeneous minibody-drug conjugate against HER2-positive breast cancer
Résumé
Trastuzumab emtansine (Kadcyla®) was the first antibody-drug conjugate (ADC) approved by the Food and Drug
Administration in 2013 against a solid tumor, and the first ADC to treat human epidermal growth factor receptor
2 positive (HER2+) breast cancer. However, this second generation ADC is burden by several limitations
included heterogeneity, limited activity against heterogeneous tumor (regarding antigen expression) and suboptimal
tumor penetration. To address this, different development strategies are oriented towards homogeneous
conjugation, new drugs, optimized linkers and/or smaller antibody formats. To reach better developed next
generation ADCs, a key parameter to consider is the management of the hydrophobicity associated with the
linker-drug, increasing with and limiting the drug-to-antibody ratio (DAR) of the ADC. Here, an innovative
branched pegylated linker was developed, to control the hydrophobicity of the monomethyl auristatin E (MMAE)
and its cathepsin B-sensitive trigger. This branched pegylated linker-MMAE was then used for the efficient
generation of internalizing homogeneous ADC of DAR 8 and minibody-drug conjugate of DAR 4, targeting HER2.
Both immunoconjugates were then evaluated in vitro and in vivo on breast cancer models. Interestingly, this study
highlighted that the minibody-MMAE conjugate of DAR 4 was the best immunoconjugate regarding in vitro
cellular internalization and cytotoxicity, gamma imaging, ex vivo biodistribution profile in mice and efficient
reduction of tumor size in vivo. These results are very promising and encourage us to explore further fragmentdrug
conjugate development.