sifalimumab sifalimumab sifalimumab is a human monoclonal antibody designed for the treatment of sle, dermatomyositis, and polymyositis. it targets interferon a. sifalimumabfab fragment of sifalimumab bound to ifn-α2a. from pdb: 4ypg​.monoclonal antibodytypewhole antibodysourcehumantargetinterferon αclinical dataatc codenoneidentifierscas number1006877-41-3 ychemspidernoneuniixoy1ya7rmckeggd09668chemical and physical dataformulac6518h10008n1724o2032s38molar mass146252.08 g·mol−1 ny (what is this?) (verify) sifalimumab was developed by medimmune; as of 2017 development had been terminated in favor of moving a competing internal product, anifrolumab, into phase iii trials.