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1074 A novel fully human CD28 antibody that cross-reacts with CTLA-4 and mouse CD28 for potential applications in cancer immunotherapy
  1. Abdullah Elsayed1,
  2. Frederik Peissert1,
  3. Louis Plüss1,
  4. Franziska Ulrich2,
  5. Emanuele Puca1,
  6. Roberto De Luca1,
  7. Cornelia Halin2 and
  8. Dario Neri3
  1. 1Philochem AG, Otelfingen, Switzerland
  2. 2Swiss Federal Institute of Technology, Zurich, Switzerland
  3. 3Philogen Spa, Otelfingen, Switzerland


Background T cell activation is initiated through engaging T cell receptor (TCR)/CD3 complex upon recognizing antigenic peptides presented by major histocompatibility complex (pMHC).1,2 However, TCR/CD3 complex alone is not sufficient for full T cell activation. In fact, the absence of an additional signal induces T cell exhaustion and thus impaired activation of T cells.3 CD28 is a crucial co-stimulatory receptor that enhances T cell proliferation, survival and production of key cytokines such as IL-2, IFN- γ, and TNF- α.4–7 Despite the potential key role of CD28 in cancer immunotherapy, there have been safety concerns following the TeGenero disaster in 2006.8 Here we describe the generation of a fully human anti-CD28 antibody named “VE19ZH”. VE19ZH features a unique combination of desirable properties in comparison to other currently available mAbs such as TGN1412.

Methods We isolated a new fully human antibody (VE19ZH) against human CD28 by phage display technology. Binding was validated by flow cytometry on primary human T cells. The co-stimulatory effect in combination with anti-CD3 (OKT3) was assessed in vitro by proliferation of human PBMCs and cytokine release. To rule out the undesirable super-agonistic effect observed by TGN1412, VE19ZH was tested for its capability to activate human PBMCs in the absence of TCR/CD3 signaling. Cross-reactivity against CTLA-4 and mouse CD28 were evaluated by ELISA and flow cytometry. Finally, the binding epitope of VE19ZH was revealed using PepSpot™ technology.

Results VE19ZH is a fully human antibody that binds selectively to both human and murine CD28. VE19ZH IgG4 exhibited a strong and significant co-stimulatory effect on human PBMCs when combined with anti-human CD3 (OKT3). Unlike TGN1412, VE19ZH did not activate T cells without TCR/CD3 signaling. In addition, VE19ZH was shown to bind to CTLA-4. VE19ZH binds to an epitope similar to the natural ligand (CD80/CD86) as revealed by PepSpot™ technology. In vitro killing activity was validated using BiTE formats and showed synergism with low concentrations of CD3 bispecifics.

Conclusions VE19ZH is a promising module for cancer immunotherapy with unique properties: (i) Fully human mAb for minimal immunogenicity (ii) Potent co-stimulator for full T cell activation (iii) Conventional agonist of CD28 and not super-agonistic like TGN1412 (iv) cross reacts with mouse CD28 for better assessment in immunocompetent mouse models (v) Binds to human CTLA-4 for potential checkpoint inhibition. The potential of VE19ZH to boost T cell response via CD28 activation and CTLA-4 blockade is currently being investigated in vitro and in vivo.


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