**Przemysław J. Kotyla 1,\*, Md Asiful Islam 2,\* and Małgorzata Engelmann <sup>3</sup>**


Received: 14 September 2020; Accepted: 3 October 2020; Published: 7 October 2020

**Abstract:** Janus kinase (JAK) inhibitors, a novel class of targeted synthetic disease-modifying antirheumatic drugs (DMARDs), have shown their safety and efficacy in rheumatoid arthritis (RA) and are being intensively tested in other autoimmune and inflammatory disorders. Targeting several cytokines with a single small compound leads to blocking the physiological response of hundreds of genes, thereby providing the background to stabilize the immune response. Unfortunately, blocking many cytokines with a single drug may also bring some negative consequences. In this review, we focused on the activity of JAK inhibitors in the cardiovascular system of patients with RA. Special emphasis was put on the modification of heart performance, progression of atherosclerosis, lipid profile disturbance, and risk of thromboembolic complications. We also discussed potential pathophysiological mechanisms that may be responsible for such JAK inhibitor-associated side effects.

**Keywords:** rheumatoid arthritis; JAK/STAT; Janus kinase inhibitors; cardiovascular system; heart failure; thromboembolic; lipid profile disturbances; cytokines
