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Molecular insights into recognition of GUCY2C by T-cell engaging bispecific antibody anti-GUCY2CxCD3

Pragya Rampuria1, Lidia Mosyak2, Adam R Root3

  • 1Biomedicine Design, Pfizer Inc., 610 Main St., Cambridge, MA, 02139, USA. pragya.rampuria@pfizer.com.

Scientific Reports
|August 17, 2023
PubMed

Insights

Researchers identified the Guanylyl Cyclase C (GUCY2C) binding epitope for a novel colorectal cancer immunotherapy. This finding is crucial for developing targeted cancer treatments and understanding antibody efficacy.

Area of Science:

  • Oncology
  • Immunology
  • Structural Biology
  • Gastroenterology

Background:

  • Guanylyl Cyclase C (GUCY2C) is a tumor-associated antigen present in gastrointestinal cancers.
  • GUCY2C is a validated target for colorectal cancer immunotherapy.
  • Bispecific antibodies (BsAbs) offer a promising therapeutic strategy for cancer treatment.

Purpose of the Study:

  • To identify the GUCY2C binding epitope of a novel anti-GUCY2CxCD3 bispecific antibody (BsAb).
  • To structurally characterize the interaction between the BsAb and its GUCY2C epitope.
  • To understand the impact of epitope positioning on the BsAb's tumor-killing activity.

Main Methods:

  • Yeast surface-display technology was employed for antibody epitope mapping.
  • An orthogonal peptide-based mapping strategy was utilized to pinpoint the binding site.
  • Crystal structures of the GUCY2C epitope-antibody complex were determined, both in minimal and full-length extracellular domain (ECD) contexts.

Main Results:

  • The GUCY2C binding epitope was localized to the N-terminal helix H2 of human GUCY2C.
  • Structural analysis revealed the epitope is on a protruding, membrane-distal helical region.
  • Epitope positioning dictates the spatial arrangement of the BsAb's antigen-binding arms, crucial for tumor cell lysis.

Conclusions:

  • The N-terminal helix H2 of GUCY2C is the key epitope for the anti-GUCY2CxCD3 BsAb.
  • The structural orientation of this epitope is critical for the BsAb's therapeutic efficacy in targeting GUCY2C-expressing tumors.
  • This detailed epitope and structural understanding facilitates the optimization of GUCY2C-targeted immunotherapies.

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