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IMPORTANCE Immunotherapy with checkpoint inhibitors targeting the PD-1 (programmed cell death 1) axis has brought notable progress in patients with non-small cell lung cancer (NSCLC) and other cancers. However, autoimmune toxic effects are frequent and poorly understood, making it important to understand the pathophysiologic processes of autoimmune adverse effects induced by checkpoint inhibitor therapy. OBJECTIVE To gain mechanistic insight into autoimmune skin toxic effects induced by anti-PD-1 treatment in patients with non-small cell lung cancer. DESIGN, SETTING, AND PARTICIPANTS This prospective cohort study was conducted from July 1, 2016, to December 31, 2018. Patients (n = 73) with non-small cell lung cancer who received anti-PD-1 therapy (nivolumab or pembrolizumab) were recruited from 4 different centers in Switzerland (Kantonsspital St Gallen, Spital Grabs, Spital Wil, and Spital Flawil). Peripheral blood mononuclear cells, tumor biopsy specimens and biopsies from sites of autoimmune skin toxic effects were collected over a 2-year period, with patient follow-up after 1 year. MAIN OUTCOMES AND MEASURES Response to treatment, overall survival, progression-free survival, and development of autoimmune toxic effects (based on standard laboratory values and clinical examinations). RESULTS Of the cohort of 73 patients with NSCLC (mean [SD] age, 68.1 [8.9] years; 44 [60%] men), 25 (34.2% [95% CI, 24.4%-45.7%]) developed autoimmune skin toxic effects, which were more frequent in patients with complete remission or partial remission (68.2% [95% CI, 47.3%-83.6%]) than those with progressive or stable disease (19.6% [95% CI, 11.0%-32.5%]) (χ 2 = 14.02, P < .001). Nine T-cell antigens shared between tumor tissue and skin were identified. These antigens were able to stimulate CD8 + and CD4 + T cells in vitro. Several of the antigen-specific T cells found in blood samples were also present in autoimmune skin lesions and lung tumors of patients who responded to anti-PD-1 therapy. CONCLUSIONS AND RELEVANCE These findings highlight a potential mechanism of checkpoint inhibitor-mediated autoimmune toxic effects and describe the association between toxic effects and response to therapy; such an understanding will help in controlling adverse effects, deciphering new cancer antigens, and further improving immunotherapy.

Background:Treatment with programmed death receptor-1 (PD-1) antibodies is associated with high response rates in patients with advanced melanoma. Reliable markers for early response and outcome are still sparse.Methods:We evaluated 66 consecutive patients with advanced/metastatic melanoma treated with nivolumab or pembrolizumab between 2013 and 2014. The main objectives of this study were to investigate whether, first, serum lactate dehydrogenase (LDH) at baseline (normal vs above the upper limit of normal) correlates with overall survival (OS), and, second, whether the change of LDH during treatment predicts response before the first scan and OS in patients with an elevated baseline LDH.Results:After a median follow-up of 9 months, patients with an elevated baseline LDH (N=34) had a significantly shorter OS compared with patients with normal LDH (N=32; 6-month OS: 60.8% vs 81.6% and 12-month OS: 44.2% vs 71.5% (log-rank P=0.0292). In those 34 patients with elevated baseline LDH, the relative change during treatment was significantly associated with an objective response on the first scan: the 11 (32%) patients with partial remission had a mean reduction of −27.3% from elevated baseline LDH. In contrast, patients with progressive disease (N=15) had a mean increase of +39%. Patients with a relative increase over 10% from elevated baseline LDH had a significantly shorter OS compared with patients with ⩽10% change (4.3 vs 15.7 months, log-rank P<0.00623).Conclusions:LDH could be a useful marker at baseline and during treatment to predict early response or progression in patients with advanced melanoma who receive anti-PD-1 therapy.