Directed-Complement Activation as a Novel Immunotherapeutic Approach for HER2-Breast Cancer.

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• Targeting tumor cells via complement activation is a key strategy for cancer elimination.
• Multimeric immunotherapeutic complexes (CoMiX) have been developed to selectively activate complement pathways on cancer cells.

Purpose of the Study:

• To generate and evaluate CoMiX that stimulate either the alternative pathway (CoMiX-FHR4) or the classical pathway (CoMiX-Fc) on HER2-expressing tumor cells.
• To compare the efficacy of CoMiX with existing therapeutic antibodies like trastuzumab and pertuzumab.

Main Methods:

• CoMiX were constructed using a C4 binding protein scaffold, incorporating Factor H Related protein 4 (FHR4) or Fc dimers with anti-HER2 VHH antibodies.
• In vitro assays assessed C3b/C5b9 deposition, complement-dependent cytotoxicity (CDC), NK cell activation, and macrophage phagocytosis.
• In vivo studies evaluated therapeutic efficacy in human BT474 tumor xenografts in nude mice.

Main Results:

• CoMiX-FHR4 variants demonstrated superior C3b/C5b9 deposition and CDC on BT474 cells compared to trastuzumab and pertuzumab.
• All CoMiX induced tumor cell death and phagocytosis; CoMiX-Fc also activated NK cells.
• In vivo, CoMiX-FHR4 showed anti-tumor effects, and CoMiX-VHH(P)/Fc matched pertuzumab's efficacy.
• Combinations of CoMiX enhanced anti-tumor activity and NK cell infiltration.
• CoMiX-FHR4 proved effective against trastuzumab-resistant xenografts, delaying tumor growth and increasing NK cell infiltration.

Conclusions:

• Directed complement activation via CoMiX represents a viable alternative to therapeutic antibodies.
• CoMiX hold potential for combination therapies, particularly in cases of resistance to standard treatments.
• These findings open new avenues for developing advanced immunotherapies against HER2-expressing tumors.