Immune checkpoint blocking in cancer therapy using thermosensitive hydrogels: a review.

Cancer is a challenging issue requiring new strategies for management and control. Immune checkpoint blockades (ICBs) increase the body's immune response against cancer by targeting specific receptors on T-lymphocytes. The FDA approved different ICBs for cancer treatment: anti-PD-1, PDL-1, and CTLA-4 inhibitors. Many immune checkpoint inhibitors (ICIs) are in clinical trials, highlighting their significance. Challenges like resistance and side effects have led researchers to explore new delivery strategies for ICIs. Thermosensitive hydrogels can change from sol to gel and vice versa due to their structure. They interact with aqueous medium through groups like ethyl, methyl, and propyl, forming hydrogen bonds. These bonds of hydrogen are temperature-sensitive and cause the change of the polymer from sol to gel at a temperature named critical solution temperature (CST). The using temperature-responsive polymers and ICBs showed a promising approach to sustained localized cancer therapy with lowering side effects on normal tissues. In this paper, we first define new investigations on immune therapy in cancer via ICBs. Then, we present recent studies of thermosensitive polymers in cancer therapy and the most used thermosensitive polymers in studies. Eventually, we discuss studies that used thermosensitive polymers in the delivery of ICBs and discuss new investigations in this field.