Definition

An injectable biodegradable hydrogel-based, intra-tumoral extended-release (ER) formulation containing the imidazoquinolinamine resiquimod, a Toll-like receptor (TLR) 7 and 8 agonist, with potential immunostimulating and antineoplastic activities. Upon intra-tumoral administration at the site and time of surgery involving transurethral resection of bladder tumor, the hydrogel-based resiquimod STM-416 locally releases resiquimod for an extended period and binds to TLR7 and 8, which are found mainly on dendritic cells (DCs), macrophages, and B lymphocytes, and activates the TLR signaling pathway. This results in the induction of the nuclear translocation of transcription activator nuclear factor kappa-B (NF-kB) and activation of other transcription factors. This leads to the induction of NF-kB-dependent genes and increases cytokine production, especially interferon-alpha (INF-a), which results in the enhancement of T-helper 1 (Th1) immune responses. Activation of DCs also results in the activation of cytotoxic T-lymphocyte (CTL) and B-lymphocyte immune responses. This may cause tumor cell lysis. TLR7 and 8, members of the TLR family, play fundamental roles in the activation of the immune system.