Albumin-binding dendritic siRNA improves delivery and efficacy to solid tumors in a melanoma model

Small interfering RNA (siRNA) therapeutics are a new class of drugs that is rapidly expanding to tackle various diseases. Extrahepatic delivery of siRNAs, especially to the parenchyma of solid tumors, is challenging with multiple strategies being explored such as lipid nanoparticle based delivery and ligand conjugation strategies. Here, we report that an albumin-binding dendritic siRNA (D-siRNA) boosts blood circulation time following systemic administration, leading to improved delivery and silencing activity in a melanoma tumor model, in comparison to non-albumin binding lipophilic siRNAs. D-siRNAs increased the tumor-to-liver delivery ratio, including both immune and non-immune cell types within the tumor parenchyma. Using D-siRNAs to target JAK1 expression as an adjuvant to immune checkpoint inhibitors, we found that D-siRNAs was able to enhance PD1 antibody treatment and slow tumor progression of melanoma. Thus, this work demonstrates the utility of D-siRNAs as a systemically administered tumor delivery strategy, enabling the use of siRNAs as chemotherapeutic agents. Further mechanistic studies into the role of JAK1 in melanoma pathology and progression may expand this into additional targets as potential treatments.