CHICAGO – Recent randomized, placebo-controlled, phase 3 trials of tocilizumab, abatacept, and riociguat for the treatment of systemic sclerosis each failed to reach its primary endpoint of change from baseline in modified Rodnan Skin Score (mRSS).
Still, findings with respect to secondary endpoints and certain exploratory outcomes suggest each of the agents holds some promise in the systemic sclerosis (SSc) arena, according to the data presented at the annual meeting of the American College of Rheumatology.
In the double-blind portion of the phase 3of 212 patients with SSc, numerical improvement was observed for the primary endpoint of mean change in mRSS from baseline to week 48 with tocilizumab versus placebo (–6.14 vs. –4.41 points, respectively). The change in the treatment group was comparable with what was seen in the phase 2 , but the decline in mRSS in the placebo group was much greater in phase 3 than in phase 2, and so the difference between the groups in the current study failed to reach statistical significance (P = .098), reported , a professor of medicine and director of the scleroderma program at the University of Michigan, Ann Arbor.
The interleukin-6 (IL-6) receptor–alpha antibody was previously shown in the faSScinate trial to lead to numeric improvements in skin thickening as measured by the mRSS, as well as to clinically meaningful lung function preservation as measured by percent predicted forced vital capacity (FVC).
In the current phase 3 study, key secondary end points also appeared to favor tocilizumab, but since the primary endpoint for mRSS was not met, all other P values cannot be considered statistically significant despite the strength of the evidence and were reported for informational purposes only, he noted.
The median cumulative distribution of change from baseline to week 48 in percent predicted FVC with tocilizumab versus placebo was –0.6 vs. –3.9, respectively (descriptive P = .0015), and the mean change from baseline in FVC at week 48 was –24 mL vs. –190 mL (difference of 167 mL in favor of tocilizumab; descriptive P = .0001).
Time to treatment failure also favored tocilizumab, he said (hazard ratio, 0.63; descriptive P = .082), he said.
Patients were randomly assigned to receive either weekly 162-mg injections of subcutaneous tocilizumab or placebo for 48 weeks. Escape therapy was allowed beginning at week 16 if patients experienced declines in FVC or beginning at week 24 if they experienced worsened mRSS or worsened SSc complications, Dr. Khanna said.
“The key part is that no immunotherapy was allowed. ... So it’s a true randomized, placebo-controlled trial,” he said.
Most (81%) of the patients were women, and they had a mean age of 48 years, mean SSc duration of 23 months, mean mRSS of 20.4 units on a 0-51 scale, and a normal mean percent predicted FVC of 82.1%.
“HAQ-DI showed moderate disability of 1.2,” he noted.
Safety in the study was consistent with that seen in prior tocilizumab studies; no new safety signals were identified. Serious adverse events occurred in 13% and 17% of tocilizumab and placebo group patients , respectively, and serious infections were reported by 7% and 2%.
Although clinically meaningful and consistent differences in FVC favoring tocilizumab were shown in this study, the primary endpoint was not met, Dr. Khanna said.
“There were no statistically significant differences, largely driven by unexpected improvement in the placebo group, which was different than what we found in [the faSScinate] trial,” he said, noting, however, that the FVC findings in the current study were clinically meaningful.
Also, in a separate presentation at the meeting, he explained that the differences favoring tocilizumab were statistically significant when patient-level data from the trial were analyzed based on the ACR Composite Response Index in Systemic Sclerosis (CRISS). Those findings provide validation of the novel outcomes measure, he said.