FRO4 Antibody

Clarification of Terminology

The term "FRO4" does not align with established antibody nomenclature or known therapeutic candidates. Possible misinterpretations include:

• FR104: A pegylated Fab' antibody targeting CD28 (discussed in ).

• FRα (Folate Receptor alpha): Targeted by monoclonal antibodies like MOv18-IgG1 for triple-negative breast cancer (TNBC) therapy .

• PF4 antibodies: Platelet factor 4-specific antibodies implicated in heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT) .

FR104: A Pegylated Fab' Antibody Targeting CD28

Key Findings:

• FR104 demonstrates immunosuppressive activity without inducing cytokine release syndrome .

• In humanized mice, it prevents GVHD in a CTLA4-dependent manner, unlike CTLA4-Ig (e.g., belatacept) .

MOv18-IgG1: Anti-Folate Receptor Alpha (FRα) Antibody

Key Findings:

• FRα antibodies may selectively target cancer cells while sparing normal tissues .

• Combining MOv18-IgG1 with Src inhibitors enhances antitumor effects .

PF4 Antibodies in HIT and VITT

Key Findings:

• Autoimmune HIT antibodies (e.g., 1C12, 1E12, 2E1) bind PF4 without heparin and activate platelets .

• VITT-associated antibodies do not cross-react with SARS-CoV-2 spike protein .

Potential Causes for the Absence of "FRO4 Antibody" Data

1. Nomenclature Errors:

   • FR104 or FRα antibodies may have been mislabeled as "FRO4".

   • Confusion with PF4 antibodies, which share the "F" prefix but target distinct antigens.

2. Proprietary or Preclinical Status:

   • "FRO4" could represent an unpublished or experimental antibody not yet disclosed in peer-reviewed literature.

3. Terminological Ambiguity:

   • The suffix "4" may denote a specific subclass, epitope, or variant, but no such classification exists in the provided sources.

Recommendations for Further Investigation

1. Verify Nomenclature: Cross-check with primary sources or confirm the intended target (e.g., CD28, FRα, PF4).

2. Explore Antibody Databases:

   • The IEDB catalogs antibody sequences and epitopes, including heavy/light chain CDR3 regions .

   • AB-Bind provides mutational binding data for antibody-antigen interactions .

3. Review Antibody Characterization Guidelines:

   • Recent initiatives (e.g., YCharOS) emphasize rigorous validation of antibody specificity and affinity .