The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved. The free-drug human samples used in this study came from healthy volunteers who signed the informed consent term approved by the local Ethics Committee of our university and tertiary hospital (Comissão de Ética para Análise de Projetos de Pesquisa–CAPPesq, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Brazil, ID #1.922.444). Plasma samples from eight patients diagnosed with cutaneous lupus erythematosus under thalidomide treatment were obtained from the sample repository of the Outpatients Rheumatology Division of the Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (São Paulo, Brazil). The patients had previously signed the informed consent term approved by the local ethics committee (#1.922.444).