Descartes-08 for Children, Adolescents and Young Adults With Childhood-onset Systemic Lupus Erythematosus, ANCA-associated Vasculitis, Juvenile Myasthenia Gravis, and Juvenile Dermatomyositis

In part 1, three different doses will be administered to 3 participants with either disease indication to establish maximum tolerated dose In part 2, the MTD established in Part-1 will be administered as six once-weekly infusions to up to 10 participants per each of four baskets (cSLE, AAV, JDM and JMG) in an outpatient setting.