First-generation and preclinical evaluation of an EphA5-targeted antibody-drug conjugate in solid tumors
Fernanda I. Staquicini, Fenny H.F. Tang, Vanessa de Oliveira, Sun-Young Kim, Ethan R. Chen, Christopher Markosian, Daniela I. Staquicini, Yongjian Wu, J. Kellogg Parsons, Kirstin F. Barnhart, Stephen C. Alley, Isan Chen, Wadih Arap, Renata Pasqualini
Fernanda I. Staquicini, Fenny H.F. Tang, Vanessa de Oliveira, Sun-Young Kim, Ethan R. Chen, Christopher Markosian, Daniela I. Staquicini, Yongjian Wu, J. Kellogg Parsons, Kirstin F. Barnhart, Stephen C. Alley, Isan Chen, Wadih Arap, Renata Pasqualini
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Research Article Oncology

First-generation and preclinical evaluation of an EphA5-targeted antibody-drug conjugate in solid tumors

Abstract

Contemporary cancer treatment strategies are shifting toward targeted therapies to improve efficacy and minimize toxicity. Here, we report the design and preclinical evaluation of MBRC-101, a first-in-class antibody-drug conjugate (ADC) targeting EphA5, a receptor tyrosine kinase with an established role in embryonic development but not extensively studied in cancer. We show that EphA5 is expressed in multiple solid tumors, including cancers of the aerodigestive (non–small cell lung, head and neck, gastric, colon, and pancreatic) and genitourinary (bladder and ovary) tracts, as well as most breast cancer subsets (including triple-negative tumors), with limited expression in normal tissues. MBRC-101 is a humanized anti-EphA5 antibody conjugated to monomethyl auristatin E (MMAE) through a ThioBridge, thereby ensuring stable drug-to-antibody ratio and reducing off-target effects. MBRC-101 showed potent antitumor activity, achieving complete tumor regression in several patient-derived xenograft models. Preclinical Good Laboratory Practice–compliant toxicology studies in rats and nonhuman primates demonstrated that MBRC-101 is well tolerated, with observed toxicities limited to known MMAE off-target effects. These findings establish EphA5 as a therapeutic target in cancer and support the translational development of MBRC-101 as a promising ADC candidate for clinical evaluation, currently in a first-in-human multicenter investigational trial for patients with advanced solid tumors (ClinicalTrials.gov, NCT06014658).

Authors

Fernanda I. Staquicini, Fenny H.F. Tang, Vanessa de Oliveira, Sun-Young Kim, Ethan R. Chen, Christopher Markosian, Daniela I. Staquicini, Yongjian Wu, J. Kellogg Parsons, Kirstin F. Barnhart, Stephen C. Alley, Isan Chen, Wadih Arap, Renata Pasqualini

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Figure 2

Identification and structural analysis of the binding epitope recognized by the anti-EphA5 antibody.

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Identification and structural analysis of the binding epitope recognized...
(A) Antibody-binding epitope of EphA5 mapped by site-directed alanine scanning. (B) AlphaFold-predicted, 3-dimensional, atomic-level structure of full-length human EphA5 containing the identified epitope (green) and excluding low-confidence regions. Consensus protein topology prediction was determined by TOPCONS. The inset visualizes the critical amino acid residues responsible for binding to the anti-EphA5 antibody (green, major binding contributor; orange, binding contributor; yellow, secondary binding contributor). (C) Schematic representation of the identified epitope (residues R306–E330) relative to the established domains of human EphA5. (D) Multiple sequence alignment of the epitope (residues R306–E330) derived from relevant EphA5 orthologs (green, major binding contributor; orange, binding contributor; yellow, secondary binding contributor). (E) Conformational similarity between the extracellular region (residues S58–P561) or epitope (residues R306–E330) of human EphA5 with its corresponding ortholog following best-fit superimposition of AlphaFold-predicted 3-dimensional atomic-level structures. Root mean square deviation was calculated for paired Cα atoms of all corresponding residues. (F) MPA confirmed dose-dependent binding specificity of the anti-EphA5 antibody to EphA5. (G) All other members of the Eph family of receptors were evaluated and did not show cross-reactivity with the anti-EphA5 antibody. SAM, sterile alpha motif.