Comparative Preclinical Evaluation of HER2-Targeting ABD-Fused Affibody® Molecules 177Lu-ABY-271 and 177Lu-ABY-027: Impact of DOTA Position on ABD Domain

Yongsheng Liu,Theresa Bengtsson,Anzhelika Vorobyeva,Annika Loftenius,Fredrik Y. Frejd,Vladimir Tolmachev,Anna Orlova,Tianqi Xu,Per Jonasson

doi:10.3390/pharmaceutics13060839

Abstract

Radiolabeled Affibody-based targeting agent 177Lu-ABY-027, a fusion of an anti-HER2 Affibody molecule with albumin binding domain (ABD) site-specifically labeled at the C-terminus, has demonstrated a promising biodistribution profile in mice; binding of the construct to albumin prevents glomerular filtration and significantly reduces renal uptake. In this study, we tested the hypothesis that site-specific positioning of the chelator at helix 1 of ABD, at a maximum distance from the albumin binding site, would further increase the strength of binding to albumin and decrease the renal uptake. The new construct, ABY-271 with DOTA conjugated at the back of ABD, has been labelled with 177Lu. Targeting properties of 177Lu-ABY-271 and 177Lu-ABY-027 were compared directly. 177Lu-ABY-271 specifically accumulated in SKOV-3 xenografts in mice. The tumor uptake of 177Lu-ABY-271 exceeded uptake in any other organ 24 h and later after injection. However, the renal uptake of 177Lu-ABY-271 was two-fold higher than the uptake of 177Lu-ABY-027. Thus, the placement of chelator on helix 1 of ABD does not provide desirable reduction of renal uptake. To conclude, minimal modification of the design of Affibody molecules has a strong effect on biodistribution, which cannot be predicted a priori. This necessitates extensive structure-properties relationship studies to find an optimal design of Affibody-based targeting agents for therapy.

Highlights

Introduction iationsTargeted therapy is a useful option for the treatment of disseminated cancer
The use of monoclonal antibodies (Mabs) may provide a more general solution as it is possible to generate high-affinity antibodies for a large variety of molecular targets
We evaluated a variant of ZHER2:2891 -albumin binding domain (ABD), where the DOTA chelator is positioned on helix one on the back of ABD, which is opposite to helix two and three and responsible for binding to albumin

Summary

Introduction

Targeted therapy is a useful option for the treatment of disseminated cancer. Impressive progress has been made in targeted radionuclide therapy [1]. The number of validated targets for therapy using radiolabeled peptides is limited. The use of monoclonal antibodies (Mabs) may provide a more general solution as it is possible to generate high-affinity antibodies for a large variety of molecular targets. Such Mabs might provide specific delivery of cytotoxic radionuclides by molecular recognition of cancer-associated antigens on the surface of malignant cells. Clinical studies on different types of human cancers revealed that the clinical effect of radioimmunotherapy (RIT) is limited to radiosensitive hematology malignancies.

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