PDCD1 and neoplasm: For melanoma, Wang and colleagues developed a biodegradable microneedle patch, composed of hyaluronic acid integrated with pH-sensitive dextran nanoparticles that encapsulate anti-PD-1, for controlled delivery of this ICI into the tumor; the results of the pre-clinical research showed enhanced retention of anti-PD-1 antibodies in the tumor and increased immune responses, compared to the intravenous (IV) administration of anti-PD-1 (60).