Engineering bispecific exosome activators of T cells to target immune checkpoint inhibitor-resistant metastatic melanoma.

Inhalable BEAT exosomes co-displaying PD-1 and FZD8 activate T cells and produce robust antitumor effects in ICI-resistant melanoma mouse models.

• Why it matters: Overcoming the immunosuppressive tumor microenvironment in ICI-resistant melanoma remains a key challenge in cancer immunotherapy. Addressing this gap could improve treatment outcomes for resistant cancers.
• What they did: Researchers engineered an inhalable exosome system called BEAT that displays PD-1 and FZD8 proteins to block PD-L1 and Wnt7b, using tandem display technology to target lung metastases in mouse models.
• The result: BEAT effectively recruits and activates CD8⁺ T cells, reprograms the tumor microenvironment, and shows superior in vivo performance compared to dual antibody treatments, suggesting broad applicability to resistant cancers.