Efficacy and Safety of Levilimab in Combination with Methotrexate in Patients with Active Rheumatoid Arthritis: 56-Week Results of Phase III Randomized Double-Blind Placebo-Controlled Trial SOLAR

Background. Previously, 24-week results of phase III double-blind, placebo-controlled randomized clinical study (SOLAR) of levilimab in subjects with active rheumatoid arthritis (RA) proved a superiority of levilimab over placebo. Here, we present 1-year efficacy and safety data of the SOLAR study. Objectives. To evaluate the efficacy and safety of levilimab in combination with methotrexate (MTX) in subjects with MTX resistant active RA. Materials and methods. The study was conducted at 21 clinical sites in Russia and Belarus. All randomized subjects have completed the study between November 2019 and October 2021. Adult subjects (154) aged >= 18 years with confirmed diagnosis of RA1 were randomly assigned (2 : 1) to receive either levilimab (162 mg, SC, QW) + MTX (n = 102) or placebo + MTX (n = 52). After W24 of the study all subjects continued to receive open label levilimab. Subjects who have achieved DAS28-CRP <= 2.6 at W24 were switched to maintenance (Q2W) regimen of levilimab at W28 (LVL QW/Q2W and PBO/LVL Q2W arms). Those with DAS28-CRP > 2.6 at W28 continued with QW regimen (LVL QW and PBO/LVL QW arm). The PBO/LVL Q2W arm contained only one subject, thus not included in the analysis. The efficacy analysis was performed in a population of all randomized subjects. Those with missing data due to study discontinuation or rescue therapy prescription were considered non-responders. Otherwise, the analysis was performed on complete cases. Safety was assessed through monitoring of adverse events (AEs) in a population of those, who received at least on dose of LVL (n = 152). Results. Better response to treatment was observed in LVL QW/Q2W as it composed of those who reach DAS28-CRP <= 2.6 at W24. At this time point 15/27 (55.6%) of them achieved ACR70; 23/27 (85.2%) achieved DAS28-CRP remission (<2.6) and 7/27 (25.9%) achieved ACR/EULAR2011 remission of RA. After switching to LVL Q2W, rates of ACR70 and DAS28-CRP<2.6 did not significantly changed until W52: 17/27 (63.0%) and 21/27 (77.8%), respectively, yet the proportion of subject with ACR/EULAR 2011 remission further increased and reached 12/27 (44.4%). LVL QW arm was diminished by subjects who achieved high response to treatment at W24 and composed LVL QW/Q2W arm. Thus, ACR70, and remissions rate in this arm was close to zero at W24. However, continuation of LVL QW in those who not achieved DAS28-CRP <= 2.6 at W24 induced ACR70 response in 37/75 (36.0%), DAS28-CRP remission in 35/75 (46.7%) and ACR/EULAR 2011 remission in 8/75 (10.7%) at W52. The most common adverse events (reported in >= 5% of subjects) were blood cholesterol increase (30.3%), ALT increase (23.0%), lymphocyte count decrease (17.1%), ANC decrease (16.4%), blood triglycerides increase (13.8%), bilirubin increase (11.2%), AST increase (9.9%), WBC decrease (9.9%), IGRA with Mycobacterium tuberculosis antigen positive (7.2%), and injection site reactions (5.9%). No deaths occurred. Conclusions. Open label period confirmed the lasting efficacy and safety of levilimab in combination with MTX in subjects with MTX resistant active RA and suggested the possibility of switching to levilimab maintenance regimen (once every 2 weeks) (Q2W) in those who achieved remission of RA at week 24.