Thirteen compounds targeting BTK in 9 indications having attained clinical trial status of phase 2 or beyond were found that encompass RA, SLE, MS, PV, SJ chronic spontaneous urticaria (CSU), idiopathic thrombocytopenia (ITP), graft versus host disease (GVHD) disease, and asthma indications (Table 1). Here, BTK is linked to acquired polycythemia vera.