A Phase I randomised open label study to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of AZD5492 following single and multiple ascending dose administration to adult participants with Systemic Lupus Erythematosus (SLE) and Idiopathic Inflammatory Myopathies (IIM)

This is a Phase I, open label study to evaluate safety and tolerability of AZD5492 in adult participants with moderate to severe Systemic lupus erythematosus/ Idiopathic inflammatory myopathy (SLE/IIM). The study consists of 2 parts. AZD5492 is an experimental drug currently being studied for its potential to treat certain types of autoimmune disease, specifically autoimmune diseases mainly driven by abnormal B cell, including SLE and IIM. B cell is a type of white blood cell that plays a crucial role in the immune system by producing antibodies to fight infections. AZD5492 is designed to engage T cells, another type of immune cell, and direct them to target and destroy B cells including abnormal B cells. This mechanism is known as a T cell-engaging antibody. By harnessing the power of the body's own immune system, AZD5492 aims to provide a more effective treatment option for patients whose autoimmune disease has not responded to conventional therapiesPart 1 will be a sequential single ascending dose (SAD) design in adult participants with SLE. Up to 6 dose levels of AZD5492 are planned to be investigated. Approximately 30 participants with SLE are planned to participate in Part 1 .Part 2 will be a multiple ascending dose (MAD) study in adult participants with SLE, who previously did not participate in Part 1, or in adult participants with IIM. After evaluating all available data including safety, tolerability, PK and PD from Part 1, the sponsor, and at the discretion of the Safety Review Committee (SRC), will employ a step-up dosing (SUD) strategy for each cohort in Part 2. In Part 2, participants will receive 2 doses of the study drug, 7 days apart.Patients will be in the study for about 222 days and have up to 12 visits.