A Keratinocyte-Tethered Biologic Enables Location-Precise Treatment in Mouse Vitiligo

Despite the central role of IFN-γ in vitiligo pathogenesis, systemic IFN-γ neutralization is an impractical treatment option owing to strong immunosuppression. However, most patients with vitiligo present with <20% affected body surface area, which provides an opportunity for localized treatments that avoid systemic side effects. After identifying keratinocytes as key cells that amplify IFN-γ signaling during vitiligo, we hypothesized that tethering an IFN-γ‒neutralizing antibody to keratinocytes would limit anti‒IFN-γ effects on the treated skin for the localized treatment. To that end, we developed a bispecific antibody capable of blocking IFN-γ signaling while binding to desmoglein expressed by keratinocytes. We characterized the effect of the bispecific antibody in vitro, ex vivo, and in a mouse model of vitiligo. Single-photon emission computed tomography/computed tomography biodistribution and serum assays after local footpad injection revealed that the bispecific antibody had improved skin retention, faster elimination from the blood, and less systemic IFN-γ inhibition than the nontethered version. Furthermore, the bispecific antibody conferred localized protection almost exclusively to the treated footpad during vitiligo, which was not possible by local injection of the nontethered anti‒IFN-γ antibody. Thus, keratinocyte tethering proved effective while significantly diminishing the off-tissue effects of IFN-γ blockade, offering a safer treatment strategy for localized skin diseases, including vitiligo.