SM03, an anti-human CD22 monoclonal antibody, for active rheumatoid arthritis: a phase II, randomized, double-blind, placebo-controlled study

Objective. SM03, a novel chimaeric mAb specific to B cell-restricted antigen CD22, has been developed to treat RA and other B-cell-related diseases. This 24-week phase II randomized, double-blind, multi-dose, placebo-controlled study aimed to evaluate the efficacy and safety of SMO3 in moderately-to-severely active RA patients in China. Methods. One hundred and fifty-six patients on background MTX were randomized in a 1:1:1 ratio to receive a cumulative dose of 3600 mg (high dose, 600 mg x 6 infusions at weeks 0, 2, 4, 12, 14 and 16) or 2400 mg SMO3 (low dose, 600 mg x 4 infusions at weeks 0, 2, 12 and 14) or the placebo. The primary outcome was the 24-week ACR 20% improvement criteria (ACR20) response rate. Safety was also assessed. Results. The 24-week ACR20 response rate was significantly higher with high- (65.3%, P =0.002) and low-dose SM03 (56.9%, P =0.024) than with placebo (34.0%), but comparable between the high- and low-dose group. The rate of adverse events was not statistically different among the high-dose group (35.3%), the low-dose group (51.9%) and the placebo group (34.6%). Thirteen (12.6%) patients receiving SM03 reported treatment-emergent infections, including 3.9% patients in the high-dose group. No patients reported severe treatment-emergent infections or malignancies. Conclusions. In active RA Chinese patients receiving background MTX, SM03 at a cumulative dose of both 2400 mg and 3600 mg is efficacious and well-tolerated throughout the 24 weeks of treatment. Moreover, SM03 has demonstrated a good safety profile.

Automated summary

This study evaluated the efficacy and safety of SM03 in Chinese patients with RA. The results showed that SM03 had good efficacy and safety at cumulative doses of 2400mg and 3600mg.