The treatment was also well-tolerated.
Researchers at RemeGen, the company developing RC18, presented the findings, “A Human Recombinant Fusion Protein Targeting B Lymphocyte Stimulator (BlyS) and a Proliferation-Inducing Ligand (APRIL), Telitacicept (RC18), in Systemic Lupus Erythematosus (SLE): Results of a Phase 2b Study,” at the 2019 American College of Rheumatology and Association of Rheumatology Professionals (ACR/ARP) Annual Meeting, held in Atlanta.
By blocking these molecules, the experimental therapy aims to suppress the development and survival of plasma cells and mature B-cells, which produce the autoantibodies that attack tissues in autoimmune diseases. RC18 has little impact on early and memory B-cells, which are important for immune defense.
The RemeGen-sponsored and pivotal Phase 2b trial (NCT02885610) compared the safety and efficacy of RC18 to a placebo, as an add-on to standard SLE therapy.
It recruited 249 adults with active SLE (ages 18-65), who were divided into four groups. Each group received a subcutaneous (under-the-skin) injection containing one of three doses of RC18 (80 mg, 160 mg, 240 mg) or placebo. Treatment was given once a week for 48 weeks.
To assess efficacy, scientists used the SLE Responder Index 4 (SRI4) score of disease activity. This common measure assesses changes in disease activity over 10 days, resolution of skin rashes, flare rate, and changes in daily oral corticosteroid doses.
A meaningful reduction in disease activity was defined as having a four or more point drop in SRI4 scores from baseline (study’s start).
Results revealed that all doses met the trial’s primary goal, with the percentage of RC18-treated patients showing a lessening in disease activity superior to that with placebo.
Overall, meaningful reduction in disease activity was achieved by 75.8% of patients taking the higher RC18 dose (240 mg), 68.3% of those on the middle dose (160 mg), 71% of patients given the lower dose (80 mg), and 33.9% of participants on a placebo.
Similar results were observed with a disease activity measure known as SELENA-SLEDAI, or Safety of Estrogens in Lupus National Assessment-Systemic Lupus Erythematosus Disease Activity Index. This index showed responses ranging from 75.8% to 79% with RC18, and 50% with placebo.
Treatment was well-tolerated, with similar reports of adverse events across the three RC18 doses and the placebo group. The most common side effects were upper respiratory tract infections and reactions at the injection site.
One patient on the higher treatment dose died, but his death was not considered to be related to treatment.
“We are very pleased with the fact that over 70% of patients who were treated with RC18 showed clinically meaningful benefit in this trial,” Di Wu, lead investigator of the trial, said in a press release.
“These data show the promise of RC18 to precisely target lupus with its novel dual-target mechanism and become a first-in-class and best-in-class treatment,” said Jianmin Fang, PhD, RemeGen’s founder and CEO.
Because this Phase 2b trial is considered pivotal, its results might be used to support a request for approval with the U.S. Food and Drug Administration.
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