Background: PD-L1 inhibitors are the components of the standard treatment options in pts with mM. Currently, there are no data about the efficacy and safety of switching the between of different anti-PD1 antibodies in pts with mM, therefore, the aim of our study was to evaluate safety and efficacy of interchangeability of nivolumab, pembrolizumab, and prolgolimab in such population. Methods: We performed a multi-institutional retrospective analysis of pts with advanced cutaneous melanoma. Inclusion criteria were as follows: histologically confirmed cutaneous melanoma, performance status ECOG 0-2, and first-line treatment with anti-PD1 antibody and switching to another anti-PD1 antibody due to economic issues with no progressive disease after initiating of immunotherapy. Primary end-point was progression-free survival (PFS), secondary end-points were rate of all grades and grade 3-4 adverse events (CTC AE 5.0). A sample size of 87 achieves 80% power to detect an equivalence difference of 15% in 3-months PFS after change of anti-PD1 antibody using a one-sided exact test with a significance level (alpha) of 0,05. These results assume a baseline proportion of 3-months PFS 0,6 and that the actual difference is 0. Results: A total of 92 patients (52% female) were included with the median age of 65 year (28-95). Number of organs with metastases 1, 2, ≥3 were in 62 (67%), 19 (21%), and 11 (12%) of pts, respectively. Liver metastases were observed in 11% of patients. Performance status ECOG 0, 1, and 2 was in 31 (34%), 58 (63%), 3 (3,2%) pts, respectively. 56 (61%) pts received nivolumab, 18 (20%) patients received pembrolizumab, 16 (17%) patients received prolgolimab, and 2 (2%) patients received atezolizumab as first-line treatment. 19 (20,6%) pts were switched to nivolumab, 18 (19,5%) pts were switched to pembrolizumab, 57 (61,9%) pts were switched to prolgolimab, and 2 (2,1%) - to atezolizumab during first-line treatment. The median duration of treatment with first anti-PD1 antibody was 8,5 months (range 1-58 months), with second PD1-inhibitor was 4,2 months (range 1-19 months), with third anti-PD1 antibody – 2,8 months (range 1-10 months). 58 (63%) patients received 2 drugs and 34 (36%) patients received 3 drugs. Within 3 months after 1 replacement of the drug, there were 82 (89.1%) pts without progression. The efficacy was not associated with type of the switched antibodies. The frequency of all AEs and AEs is 3-4. on the first drug was 16.3% and 1.1%, when switching to the second drug - 10.8% and 0%, when switching to the third drug 3.2% and 0%. Conclusions: Our data indicate that it is possible to switch from one anti-PD1 antibody to another in first-line therapy in pts with mM without progression when limited access to anti-PD1 antibodies exists. Further randomized studies are needed to determine the efficacy of such switching strategy of ICIs.