Affibody-Derived Drug Conjugates Targeting HER2: Effect of Drug Load on Cytotoxicity and Biodistribution.

Haozhong Ding,Tianqi Xu,Maryam Oroujeni,Anzhelika Vorobyeva,Torbjörn Gräslund,Vladimir Tolmachev,Jie Zhang,Anna Orlova

doi:10.3390/pharmaceutics13030430

Abstract

Affibody molecules hold great promise as carriers of cytotoxic drugs for cancer therapy due to their typically high affinity, easy production, and inherent control of the drug molecules’ loading and spatial arrangement. Here, the impact of increasing the drug load from one to three on the properties of an affibody drug conjugate targeting the human epidermal growth factor receptor 2 (HER2) was investigated. The affibody carrier was recombinantly expressed as a fusion to an albumin-binding domain (ABD) for plasma half-life extension. One or three cysteine amino acids were placed at the C-terminus to which cytotoxic mcDM1 molecules were conjugated. The resulting drug conjugates, ZHER2–ABD–mcDM1 and ZHER2–ABD–mcDM13, were characterized in vitro, and their biodistribution in mice carrying HER2-overexpressing SKOV3 xenografts was determined. Increasing the drug load from one to three led to a decrease in affinity for HER2, but a significantly more potent cytotoxic effect on SKOV3 cells with high HER2 expression. The difference in cytotoxic effect on other cell lines with high HER2 expression was not significant. In vivo, an increase in drug load led to a 1.45-fold higher amount of cytotoxic mcDM1 delivered to the tumors. The increase in drug load also led to more rapid hepatic clearance, warranting further optimization of the molecular design.

Highlights

Drug conjugates consisting of a cancer-cell-specific targeting domain coupled to a toxic molecule have been the focus of intense research and clinical development during the last few decades
We have previously investigated the properties and therapeutic potential of anti-human epidermal growth factor receptor 2 (HER2) affibody molecules equipped with a single mcDM1 drug molecule, so-called affibody-derived drug conjugate (AffiDC) [15,16,17]
This study aimed to examine the effect of drug loading on biochemical characteristics, in vitro cytotoxic efficacy, cellular processing, and in vivo biodistribution by comparing AffiDCs with one or three mcDM1 molecules

Summary

Introduction

Drug conjugates consisting of a cancer-cell-specific targeting domain coupled to a toxic molecule have been the focus of intense research and clinical development during the last few decades. Antibody–drug conjugates (ADCs), where a monoclonal antibody (mAb) is linked to a cytotoxic drug, have been the most successful for cancer therapy [1]. By combining the specificity of an antibody and the cytotoxic activity of a drug agent, a broad therapeutic window can be obtained by a dramatic reduction in systemic toxicity compared to classical chemotherapy [2]. An example of an ADC is trastuzumab emtansine (T-DM1), consisting of the monoclonal antibody trastuzumab targeting the human epidermal growth factor receptor 2 (HER2) linked with the maytansine derivate DM1 [3]. T-DM1 is approved for therapy of HER2-positive metastatic breast cancer by the US Food and Drug Administration.

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