In mice bearing B16F10 tumors, Francis et al. observed that i.t. rather than i.p. administration of anti-PD-1 and anti-CTLA-4 (ICB) mAbs extended survival, increased CD8+ T cell tumor infiltration, and boosted CD8+ T cell proliferation both in tumors and tumor-draining lymph nodes (TDLNs). Compared to i.p., local (i.t. or ipsilateral intradermal) injection improved TDLN mAb accumulation and efficacy in multiple tumor models. Local delivery was effective at lower doses, was independent of mAb capability to deplete Tregs, and reduced toxicity biomarkers. A hydrogel formulation sustained ICB release, increasing LN delivery and tumor control.
Contributed by Alex Najibi
ABSTRACT: Systemic administration of immune checkpoint blockade (ICB) monoclonal antibodies (mAbs) can unleash antitumor functions of T cells but is associated with variable response rates and off-target toxicities. We hypothesized that antitumor efficacy of ICB is limited by the minimal accumulation of mAb within tissues where antitumor immunity is elicited and regulated, which include the tumor microenvironment (TME) and secondary lymphoid tissues. In contrast to systemic administration, intratumoral and intradermal routes of administration resulted in higher mAb accumulation within both the TME and its draining lymph nodes (LNs) or LNs alone, respectively. The use of either locoregional administration route resulted in pronounced T cell responses from the ICB therapy, which developed in the secondary lymphoid tissues and TME of treated mice. Targeted delivery of mAb to tumor-draining lymph nodes (TdLNs) alone was associated with enhanced antitumor immunity and improved therapeutic effects compared to conventional systemic ICB therapy, and these effects were sustained at reduced mAb doses and comparable to those achieved by intratumoral administration. These data suggest that locoregional routes of administration of ICB mAb can augment ICB therapy by improving immunomodulation within TdLNs.