An engineered inhalable exosome platform delivered a bispecific T‑cell activator to pembrolizumab‑resistant metastatic melanoma in preclinical models, reactivating tumor‑infiltrating T cells and showing anti‑tumor activity. The work, published in Nature Biotechnology, details formulation, dual targeting of the tumor microenvironment, and inhalation delivery to reach lung metastases. The research group demonstrated that exosome carriers can present bispecific activation signals to T cells while addressing immune‑checkpoint inhibitor resistance mechanisms, positioning inhalable biologics as a potential route for treating metastatic pulmonary disease.