Methotrexate (MTX) efficacy in the treatment of rheumatoid arthritis (RA) is variable and unpredictable, resulting in a need to identify biomarkers to guide drug therapy. This study evaluates changes in the plasma metabolome associated with response to MTX in RA with the goal of understanding the metabolic basis for MTX efficacy towards the identification of potential metabolic biomarkers of MTX response. Plasma samples were collected from healthy control subjects (n = 20), and RA patients initiating MTX therapy (n = 20, 15 mg/week) before and after 16 weeks of treatment. The samples were analyzed by a semi-targeted metabolomic analysis, and then analyzed by univariate and multivariate methods, as well as an enrichment analysis. An MTX response was defined as a clinically significant reduction in the disease activity score in 28 joints (DAS-28) of greater than 1.2; achievement of clinical remission, defined as a DAS-28 < 2.6, was also utilized as an additional measure of response. In this study, RA is associated with an altered plasma metabolome that is normalized following initiation of MTX therapy. Metabolite classes found to be altered in RA and corrected by MTX therapy were diverse and included triglycerides (p = 1.1 × 10−16), fatty acids (p = 8.0 × 10−12), and ceramides (p = 9.8 × 10−13). Stratification based on responses to MTX identified various metabolites differentially impacted in responders and non-responders including glucosylceramides (GlcCer), phosphatidylcholines (PC), sphingomyelins (SM), phosphatidylethanolamines (PE), choline, inosine, hypoxanthine, guanosine, nicotinamide, and itaconic acid (p < 0.05). In conclusion, RA is associated with significant alterations to the plasma metabolome displaying at least partial normalization following 16 weeks of MTX therapy. Changes in multiple metabolites were found to be associated with MTX efficacy, including metabolites involved in fatty acid/lipid, nucleotide, and energy metabolism.

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Immune checkpoint inhibitors, including antiprogrammed death cell protein 1 (anti-PD-1) and anti cytotoxic T-lymphocyte-associated protein 4 (anti-CTLA-4), have been associated with a range of autoimmune-related side effects since their introduction in cancer treatment. Small vessel digital necrosis, referred to as the acral vascular syndrome, is a rare but serious complication that can result in loss of digits. Here we present a case report of acral vascular syndrome and review possible aetiologies. A 45- year-old woman with invasive ductal carcinoma of the left breast presented to the emergency department during neoadjuvant treatment with carboplatin, docetaxel and pembrolizumab with complaints of severe pain in her right third digit. She had physical findings consistent with ischaemic necrosis and gangrene of the distal phalanx. Angiography demonstrated Raynaud’s phenomenon in the distal portion of the digits. Laboratory testing showed a weakly positive RNA polymerase III antibody level. Her case resulted in surgical amputation of her affected digit after partial resolution of symptoms with prednisone, vasodilators and antibiotics.

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