Safe and effective immunostimulatory therapy through vector-controlled cytokine delivery

Systemic administration of interleukin (IL)-12 has been shown to induce potent anti-tumor immune responses in preclinical cancer models. Previous clinical trials using bolus IL-12 injection through maximal tolerable dosing (MTD) strategies indicated limited efficacy alongside unwanted side-effects. Our group developed IL-12-loaded PLGA nanospheres (IL12ns) that release their contents systemically in a slow, controlled manner. An immune diagnostic platform (IDP), capable of monitoring therapeutic response through peripheral blood sampling, was designed alongside this immunostimulatory therapy. The systemic immune responses from MTD and IL12ns dosing strategies were analyzed using this IDP in healthy mice. Importantly, the MTD was associated with aberrant peripheral immune stimulation, evidenced by increased IL-12, interferon gamma (IFNG), and IL-10 signaling. The immune-protective effects of IL12ns were supported by increases in pro-inflammatory plasma cytokines/chemokines without the maladaptive transcriptomic signatures in circulating peripheral immune cells. These data ultimately support the necessity of a vector system for safe immunostimulatory IL-12 therapy. Overall design: The purpose of this study was to assess the immunotoxicity of the IL12ns vector system in healthy BALB/c mice through repeated blood sampling over three weeks. Both systemic and tissue-resident immune responses to IL12ns therapy, delivered at three doses (10, 0.1, and 0.001 mg), were compared to a daily MTD dosing strategy (10,000 ng/kg/day IL-12 – positive control) and control (negative) control. The systemic IDP analysis included bulk PBMC RNA sequencing. Following peripheral blood processing into a PBMC single cell suspension, total RNA was isolated for downstream polyA mRNA sequencing.