# Developing and Characterizing the Tumor-Targeting Efficiency of an Anti-EphA2-CD11b Bispecific Antibody

## TL;DR

This study develops a bispecific antibody that targets both EphA2 and CD11b to deliver treatments to tumors, showing it can be optimized for better tumor targeting.

## Contribution

The paper introduces a novel bispecific antibody targeting EphA2 and CD11b for tumor-specific delivery and demonstrates its optimization strategies.

## Key findings

- The bispecific antibody showed high tumor uptake in xenograft models at 4, 24, and 48 hours post-injection.
- Blocking CD11b with nonradiolabeled antibodies increased tumor targeting while reducing uptake in CD11b-rich organs.
- Lower molar activity improved tumor accumulation and reduced uptake in non-target organs.

## Abstract

Targeting molecules, such as antibodies
and peptides, play a key
role in the precise delivery of cytotoxic payloads to tumor sites
by binding to specific tumor-associated antigens or other proteins
within the tumor microenvironment. This investigation evaluates the
potential therapeutic application of a bispecific antibody (BsAb),
which simultaneously targets EphA2, a tumor-associated antigen, and
CD11b, a protein expressed by tumor-associated macrophages and myeloid-derived
suppressor cells (TAMCs). Recombinantly produced anti-EphA2-CD11b-BsAb
was conjugated to a bifunctional chelator, NOTA-SCN, and then radiolabeled
with copper-64 (64Cu). The [64Cu]­Cu-NOTA-anti-EphA2-CD11b-BsAb
radioimmunoconjugate was subsequently administered to HT1080-fibrosarcoma-bearing
nude mice via tail vein injection. Positron Emission Tomography (PET)
and ex vivo biodistribution analyses were performed to determine tumor
uptake and pharmacokinetic localization. At 4, 24, and 48 h postinjection
(p.i.), the percent injected dose per gram (%ID/g) of [64Cu]­Cu-NOTA-anti-EphA2-CD11b-BsAb in HT1080 xenografts were 5.35 ±
2.24, 4.44 ± 1.90, and 4.10 ± 0.60, respectively. There
was high uptake in the liver as well as in CD11b-expressing organs,
including the spleen, bone marrow, and lung. Binding in these CD11b-rich
organs was significantly reduced by coadministering the dose with
nonradiolabeled anti-CD11b-IgG and anti-EphA2-CD11b-BsAb, with a concurrent
increase in tumor uptake compared to nonblocked mice (8.39 ±
1.37%ID/g for blocked and 4.44 ± 1.90%ID/g for nonblocked at
24 h p.i., p = 0.0175). Further optimization studies
showed that at lower molar activity (3.7 MBq/nmol, 100 μCi/nmol),
there were significantly higher tumor accumulations and reduced uptake
in CD11b-expressing organs compared to higher molar activity (22.2
MBq/nmol, 600 μCi/nmol). Anti-EphA2-CD11b-BsAb is a functional
targeting molecule and would require optimization through molar activity
or blocking with nonradiolabeled antibody to maximize tumor targeting.