simtuzumab simtuzumab simtuzumab (inn; formerly gs 6624) is a humanized monoclonal antibody designed for the treatment of fibrosis. it binds to loxl2 and acts as an immunomodulator. in january 2016, gilead sciences terminated its phase 2 clinical study in patients with idiopathic pulmonary fibrosis (ipf) due to lack of efficacy. simtuzumabmonoclonal antibodytypewhole antibodysourcehumanizedtargetloxl2clinical dataatc codenoneidentifierscas number1318075-13-6iuphar/bps8412chemspidernoneunii11z5aiu653chemical and physical dataformulac6558h10134n1736o2037s50molar mass147492.33 g·mol−1