Melanoma is one of the most common malignant tumors. The anti-PD-1 antibody is 
used for the treatment of metastatic melanoma. Treatment success is only 35-40% 
and a range of immune-related adverse reactions can occur. Combination of 
anti-PD1 antibody therapy with other oncology therapies has been attempted. 
Herein, we assessed whether chlorogenic acid liposomes modified with sialic acid 
(CA-SAL) combined with anti-PD1 antibody treatment was efficacious as 
immunotherapy for melanoma. CA-SAL liposomes were prepared and characterized. In 
a mouse model of B16F10 tumor, mice were treated with an anti-PD1 antibody, 
CA-SAL, or combination of CA-SAL + anti-PD1 antibody, and compared with no 
treatment controls. The tumor inhibition rate, tumor-associated macrophages 
(TAMs) phenotype, T-cell activity, and safety were investigated. We observed a 
significant decrease in the proportion of M2-TAMs and CD4+Fop3+ T cells, while 
there was a significant increase in the proportion of M1-TAMs and CD8+ T cells, 
and in the activity of T cells, and thus in the tumor inhibition rate. No 
significant toxicity was observed in major organs. CA-SAL and anti-PD1 Ab 
combination therapy presented synergistic anti-tumor activity, which enhanced 
the efficacy of the PD-1 checkpoint blocker in a mouse model of melanoma. In 
summary, combination immunotherapy of CA-SAL and anti-PD1 Ab has broad prospects 
in improving the therapeutic effect of melanoma, and may provide a new strategy 
for clinical treatment.