(21a) Engineering a High Affinity Cross-Reactive Antibody to Bind VEGF-a and PlGF-2

Antibodies that restrict blood vessel growth, such as those binding vascular endothelial growth factor alpha (VEFG-A) have shown promise in treating glioblastoma. When the anti-VEGF-A antibody, Bevacizumab, was given to adult glioblastoma patients, tumor size was temporarily reduced until tumors developed mutational resistance and compensated by overproduction for the loss of VEGF-A effects by overproducing other proliferative cytokines, including placental growth factor (PlGF)¹. A study on twelve human tumor cell lines identified three (DU4475, Caki-1, SKUT1b) that were growth inhibited by anti-PlGF antibody C9v2². However, subsequent treatment of multiform glioblastoma with the anti-PlGF antibody TB-403 in conjunction with Bevacizumab, which block the PlGF-NRP1 and VEGF-VEFGR1 interactions, respectively, was unsuccessful due to a drug-drug interaction that resulted in blockade of VEGF-A activities only³.The structural homologies between VEGF and PlGF and the fact that each cytokine is able to bind the VEGFR1 and NRP1 receptors, led us to hypothesize that a single antibody binding these shared epitopes may have therapeutic potential to treat glioblastoma (Figure 1).

Towards this goal, we report the discovery of novel antibodies that block PlGF-NRP1 binding. Two antibodies recognize the human and mouse PlGF alleles with high affinity to support antibody development using mouse models of disease. A third antibody shows cross-reactive binding between human PlGF-1 and PlGF-2 isoforms. These antibodies were discovered using phage display of immune libraries generated from mice immunized with human PlGF-2. The antibodies bind PlGF with high affinities and specificities, as measured by biolayer interferometry, and the epitopes have been initially identified. Their biological activity to block cellular proliferation in vitro using DU4475 breast carcinoma cells will be shown and compared to the anti-PlGF antibody C9v2 and Bevacizumab. Future work will include phage display of the immunized human PlGF mouse library for cross reactive clones between VEGF-A and PlGF. In addition, the therapeutic potential of all discovered PlGF antibodies will be tested in a human glioblastoma xenograft mouse model. These data support development of a potent cross-reactive antibody able to simultaneously block PlGF and VEGF activities.

References:

[1] Lee et al Clin. Cancer Res. Off. J. Am. Assoc. Cancer Res. 2018, 24 (19), 4643–4649.

[2] Yao et al Proc. Natl. Acad. Sci. U. S. A. 2011, 108 (28), 11590–11595.

[3] Wang et al Cancer Chemother. Pharmacol. 2017, 79 (4), 661–671.