Dr. Jayne
Study design is a challenge for any manufacturer attempting to develop a product to potentially decrease steroid use because the FDA does not accept steroid sparing as an assessable outcome for clinical trials. For example, in the GiACTA trial, the phase 3 trial used as evidence for approval of tocilizumab for patients with giant cell arteritis, the biotechnology company Genentech wanted to give tocilizumab and demonstrate patients could then be safely taken off glucocorticoids. But the FDA required a more complicated multi-arm design.5
Other issues come up because of the way glucocorticoids have been used historically. Although they have been used for vasculitis since before drug licensing was introduced, glucocorticoids are not themselves licensed for ANCA-associated vasculitis, which brings up certain regulatory barriers in study design. Additionally, the efficacy of glucocorticoids in vasculitis to control disease activity or prevent relapse has never been officially quantified in a placebo-controlled trial.
ADVOCATE Design
For avacopan, ChemoCentryx based its application on a single phase 3 trial and two phase 2 trials.1-3 In pre-meeting documents and during the meeting itself, the company drew comparisons to the RAVE trial, used to establish the non-inferiority of rituximab to standard cyclophosphamide therapy in patients with ANCA-associated vasculitis.6 In this case, a single phase 3 trial (with supporting phase 2 data) was used as evidence for approval of rituximab.
The phase 3 trial of avacopan, ADVOCATE, used a similar, double-blind, double-dummy design.1 ADVOCATE included 331 patients with either new or relapsing ANCA-associated vasculitis. Half the participants received 30 mg of avacopan twice a day orally, as well as a prednisone placebo, out to the study’s end at 12 months. The other half received oral prednisone (tapered to 0 mg at five months) plus an avacopan placebo.
Dr. Chung
Additionally, patients received immunosuppressive treatment, either cyclophosphamide (35%) or rituximab (65%), at the discretion of the prescribing physician. Patients who had received cyclophosphamide also received follow-up azathioprine at week 15. But after initial treatment, no patients received maintenance rituximab, as would now be common practice.
Prior to enrollment, many participants were already receiving glucocorticoids as part of their treatment, to help get their disease under control. Thus, open-label prednisone treatment continued to be tapered for the early part of the trial in both groups up to the end of week 4. This had to be tapered to 20 mg or less of prednisone daily before beginning the trial, in both treatment groups.
As reported by the investigators, at week 26, the avacopan group was non-inferior to the prednisone group in terms of sustained remission. At the study’s conclusion at week 52, 66% of patients in the avacopan group were in sustained remission, as were 55% of those in the prednisone group. Thus, in terms of remission, avacopan was superior to glucocorticoids at week 52 (P=0.007).
The researchers also provided encouraging secondary endpoints related to a number of other parameters, including reduced glucocorticoid-related toxicities, fewer relapses, better quality of life measures and improvements in kidney functioning (e.g., glomerular filtration rate changes).
David R.W. Jayne, MD, a professor of clinical autoimmunity at the University of Cambridge and director of the Vasculitis and Lupus Service at Addenbrooke’s Hospital, Cambridge, England, was one of the ADVOCATE investigators and says that in the context of previous vasculitis trials, which have only rarely displayed positive effects from interventions, the ADVOCATE results are impressive.
“We’ve never seen quality-of-life benefits or [glomerular filtration rate] recovery benefits in other vasculitis trials, but we saw them consistently in this one,” says Dr. Jayne.
