Glucocorticoid Toxicity Index scores by domain in patients with antineutrophil cytoplasmic antibody-associated vasculitis treated with avacopan versus standard prednisone taper: post-hoc analysis of data from the ADVOCATE trial

Diagnosis and management of ANCA-associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis consists of two main diseases, granulomatosis with polyangiitis and microscopic polyangiitis, and remains among the most devastating and potentially lethal forms of autoimmune inflammatory disease. Granulomatosis with polyangiitis and microscopic polyangiitis are characterised by a necrotising vasculitis that can involve almost any organ, and have generally been studied together. The diseases commonly affect the kidneys, lungs, upper respiratory tract, skin, eyes, and peripheral nerves. Granulomatous inflammation and multinucleated giant cells are key pathological hallmarks of granulomatosis with polyangiitis, but are absent in microscopic polyangiitis. Many immune system events are essential to disease aetiopathogenesis, such as activation of the alternative complement pathway, neutrophil activation via complement receptors, and the influx of inflammatory cells, including monocytes and macrophages. These cells perpetuate inflammation and lead to organ damage. During the 21st century, the management of ANCA-associated vasculitis has moved away from reliance on cytotoxic medications and towards targeted biological medications for both the induction and maintenance of disease remission. Earlier diagnosis, partly the result of more reliable ANCA testing, has led to improved patient outcomes and better survival. Reductions in acute disease-related mortality have now shifted focus to long-term morbidities related to ANCA-associated vasculitis and their treatments, such as chronic kidney disease and cardiovascular disease. Therapeutic approaches in both clinical trials and clinical practice still remain too reliant on glucocorticoids, and continued efforts to reduce toxicity from glucocorticoids remain a priority in the development of new treatment strategies.

The Glucocorticoid Toxicity Index-Metabolic Domains, an abridged version of the Glucocorticoid Toxicity Index: post-hoc analysis of data from the ADVOCATE trial

BACKGROUND

Quantifying glucocorticoid toxicity is crucial to efforts to reduce it. The Glucocorticoid Toxicity Index (GTI) measures toxicity effectively in clinical trials by calculating two scores: the cumulative worsening score (CWS) and the aggregate improvement score (AIS). However, in clinical practice, high patient volumes limit the time available for standardised assessments. We aimed to compare the GTI with an abbreviated version of the GTI, the GTI-Metabolic Domains (GTI-MD), which could help to address this issue by using data that are collected easily at routine visits and do not require additional effort from clinicians.

METHODS

We did a post-hoc analysis of data from ADVOCATE, a randomised, double-blind, double-dummy, phase 3 trial in which avacopan replaced a standard prednisone taper in patients with antineutrophil cytoplasmic antibody-associated vasculitis. We calculated the cumulative worsening score (CWS) and aggregate improvement score (AIS) for each domain of the GTI-MD-comprising the BMI, glucose tolerance, blood pressure, and lipid metabolism domains of the GTI-to test its ability to differentiate the avacopan and prednisone groups by glucocorticoid toxicity. Data from two additional disease cohorts, one comprising patients with asthma and the other comprising patients with autoimmune blistering disease, constituted the validation set.

FINDINGS

Complete data were available for 321 (97%) of the 330 participants comprising the intention-to-treat population in the ADVOCATE trial at week 13, and 307 (93%) at week 26; data from these individuals were included in our post-hoc analysis. In ADVOCATE, 98 (59%) of 166 participants in the avacopan group were men and 68 (41%) were women, 88 (54%) of 164 in the prednisone group were men and 76 (46%) were women; the mean age of participants was 61·2 years [SD 14·6] in the avacopan group and 60·5 years [14·5] in the prednisone group. The validation cohort included 159 patients (89 with glucocorticoid-dependent asthma, of whom 40 [45%] were men and 49 [55%] were women, and 70 with autoimmune blistering disease of the skin, of whom 30 [43%] were men and 40 [57%] were women). The Spearman's rank correlation coefficient in ADVOCATE for the GTI-MD CWS with the GTI CWS for the treatment groups combined was 0·78 (95% CI 0·75-0·81; p<0·0001). The corresponding correlation for the AIS was 0·73 (0·69-0·77, p<0·0001). The GTI-MD distinguished the groups by glucocorticoid toxicity at both 13 weeks and 26 weeks. The mean GTI-MD CWS was lower in the avacopan group than in the prednisone group, consistent with less toxicity (15·9 vs 23·0 at 13 weeks [p=0·0010]; 26·7 vs 31·7 at 26 weeks [p=0·0092]). The GTI-MD AIS values were also consistent with less toxicity in the avacopan group (2·5 vs 13·0 at 13 weeks [p=0·0003], 4·4 vs 10·1 at 26 weeks [p=0·027]). A GTI-MD score of 0 corresponded to a low likelihood of toxicity in the other GTI domains. In the validation set, the Spearman's rank correlation coefficient for the GTI-MD CWS with the GTI CWS was 0·61 (95% CI 0·50-0·70; p<0·0001) and the corresponding correlation for the AIS was 0·58 (0·47-0·68; p<0·0001).

INTERPRETATION

The GTI-MD correlates well with the full GTI and could be incorporated readily into routine clinic workflows without additional input from the clinician. Using the GTI-MD on the background of electronic medical records systems could help clinicians to monitor glucocorticoid toxicity longitudinally, with the goals of preventing the burden of chronic, treatment-related harms and reducing long-term costs to health systems.

FUNDING

ChemoCentryx.