Targeting HER2 Expressing Tumors with a Potent Drug Conjugate Based on an Albumin Binding Domain-Derived Affinity Protein.

Javad Garousi,Tianqi Xu,Sophia Hober,Emma Von Witting,Torbjörn Gräslund,Maryam Oroujeni,Haozhong Ding,Vladimir Tolmachev,Anzhelika Vorobyeva,Anna Orlova

doi:10.3390/pharmaceutics13111847

Abstract

Albumin binding domain derived affinity proteins (ADAPTs) are a class of small and folded engineered scaffold proteins that holds great promise for targeting cancer tumors. Here, we have extended the in vivo half-life of an ADAPT, targeting the human epidermal growth factor receptor 2 (HER2) by fusion with an albumin binding domain (ABD), and armed it with the highly cytotoxic payload mertansine (DM1) for an investigation of its properties in vitro and in vivo. The resulting drug conjugate, ADAPT6-ABD-mcDM1, retained binding to its intended targets, namely HER2 and serum albumins. Further, it was able to specifically bind to cells with high HER2 expression, get internalized, and showed potent toxicity, with IC50 values ranging from 5 to 80 nM. Conversely, no toxic effect was found for cells with low HER2 expression. In vivo, ADAPT6-ABD-mcDM1, radiolabeled with 99mTc, was characterized by low uptake in most normal organs, and the main excretion route was shown to be through the kidneys. The tumor uptake was 5.5% ID/g after 24 h, which was higher than the uptake in all normal organs at this time point except for the kidneys. The uptake in the tumors was blockable by pre-injection of an excess of the monoclonal antibody trastuzumab (having an overlapping epitope on the HER2 receptor). In conclusion, half-life extended drug conjugates based on the ADAPT platform of affinity proteins holds promise for further development towards targeted cancer therapy.

Highlights

In recent years, delivery of payloads such as toxins, radionuclides, and cytotoxic drugs to cancer cells by affinity proteins have proven to be an efficient route for targeted cancer therapy
We have previously evaluated different aspects of molecular design of ADAPT6 for radionuclide molecular imaging and have found that ADAPT6 preserves binding to the human epidermal growth factor receptor 2 (HER2) target, even after chemical modification such as conjugation with different chelators [19,20,21,22,23,24]
A non-toxic control was created, where the C-terminal cysteine of ADAPT6-albumin binding domain (ABD) was alkylated with iodoacetamide (Figure 1A)

Summary

Introduction

Delivery of payloads such as toxins, radionuclides, and cytotoxic drugs to cancer cells by affinity proteins have proven to be an efficient route for targeted cancer therapy. Such constructs have become promising agents for the treatment of disseminated cancers [1]. One of the well-studied receptors for targeted cancer therapy is the human epidermal growth factor receptor 2 (HER2), which belongs to the tyrosine kinase receptor family It is overexpressed in a number of breast, ovarian, lung, and gastrointestinal cancers [2,3].

Methods

Results

Conclusion