Abstract
Objective
To evaluate belimumab addition to the standard of care in patents with refractory idiopathic inflammatory myopathy (IIM).
Methods
We conducted a 40-week multicentre, randomized, double-blind, placebo-controlled trial with 1:1 IV belimumab 10 mg/kg or placebo randomization and a 24-week open-label extension. Clinical responses were measured by the definition of improvement (DOI) and total improvement score (TIS). Flow cytometry analyses were performed on available samples before randomization, at 24 and 60–64 weeks. Descriptive statistics, t-test, Fisher’s exact test and analysis of variance tests were used.
Results
A total of 17 patients were randomized, 15 received five or more doses of belimumab or placebo and were included in the intention-to-treat analysis. More belimumab patients vs placebo attained a TIS ≥40 [55.5% vs 33.3%; P = non-significant (NS)] and achieved the DOI (33.3% vs 16.7%; P = NS) at weeks 40 and 64; the mean TIS was similar among groups. Two patients achieved major responses (TIS = 72.5) after week 40 in the belimumab arm and none in the placebo arm. No improvement in the placebo arm after switching to the open-label phase was observed. There was no steroid-sparing effect. No new safety signals were detected. Although total B cells were not reduced, belimumab induced naïve B cell depletion while enhancing the number and frequency memory B cells.
Conclusion
The study did not meet the primary endpoint and no statistically significant differences were observed in clinical responses between arms. More patients achieved sustained TIS ≥40 and reached the DOI. Most patients who received belimumab for >40 weeks had clinical improvement. Phenotypic changes in B cell populations were not associated with clinical responses.
Clinical trial registration number
Clinicaltrials.gov (https://clinicaltrials.gov/), NCT02347891
Keywords: clinical trial, myositis, belimumab, B cells
Rheumatology key messages.
More refractory IIM patients improved after belimumab vs placebo with no statistically significant difference.
Biological effects of belimumab on B cell subsets did not correlate with clinical response.
No new safety signals were identified.
Introduction
Idiopathic inflammatory myopathy (IIM) is a rare systemic inflammatory disorder characterized by chronic inflammation of muscle tissue accompanied by variable degrees of rash. When multisystem involvement (lungs, heart, intestinal tract) occurs, significant disability may ensue. The management of this condition remains challenging. No standardized guidelines for the treatment of IIM exist; therapy usually includes steroids, IVIG and various immunosuppressive (IS) agents. Based on a post hoc analysis of the clinical trial of rituximab in IIM [1] as well as multiple case series [2–5], B cell depletion with rituximab has been used in refractory cases.
Recent evidence highlights the important role of B cells and the B cell activating factor (BAFF) pathway in the pathogenesis of IIM. Greater than 10-fold elevations of serum concentrations of circulating BAFF levels were observed in patients with DM or PM [6], and this independently correlated with myositis disease activity [7]. Patients with DM as well as anti-Jo-1-positive patients had the highest BAFF serum concentrations [7, 8]. IIM patients were also noted to have a marked up-regulation of the BAFF transcript and high expression of BAFF receptor (BAFF-R) on B cells and plasma cells infiltrating muscle tissues [9, 10]. There are limited data on BAFF expression in patients with PM or DM on IS therapy and B cell–depleting agents. Higher doses of corticosteroids are reported to be associated with a significant decrease in BAFF levels in patients with IIM [8]. Interestingly, in a subset of IIM patients with necrotizing myopathy, poor responses to IS therapy correlated with high BAFF-R expression and B lymphocyte infiltration in muscle tissue [11]. Since these observations suggest a possible contribution of the BAFF pathway to the pathogenesis of IIM, it was scientifically justified to investigate this pathway with the ultimate goal of increasing our IIM therapeutic armamentarium.
This study is the first proof-of-concept trial to evaluate the biologic effects and clinical responses to the administration of belimumab, a human IgG1 monoclonal anti-BAFF antibody in addition to the standard of care (SoC) in adults with refractory IIM.
Methods
Trial design
The objectives of this multicentre, double-blind, placebo-controlled clinical trial were to compare the clinical response rates, safety and biologic responses to monthly IV belimumab vs placebo in patients with refractory IIM on stable SoC treatment. Patients on SoC were randomized 1:1 to IV belimumab 10 mg/kg or placebo for 40 weeks followed by a 24-week open-label phase during which all patients received belimumab 10 mg/kg. A loading schedule of infusions every 2 weeks × 3 was used in the initial phase of the study, followed by infusions every 4 weeks throughout the transition to the open-label phase (Supplementary Fig. S1, available at Rheumatology online). Randomization was done according to two stratification variables: disease type (PM or DM) and number of IS agents used by the patient over the last year, not including corticosteroids (≤1 IS agent and >1 IS agent).
Ethics
Our study complied with the Declaration of Helsinki. The locally appointed ethics committee—Northwell Health IRB—approved the research protocol. Written informed consent was obtained from the subjects.
Patients
Patients ≥18 years of age with a diagnosis of definite or probable DM or PM according to the Bohan and Peter criteria and validated by EULAR/ACR classification criteria who were positive for at least one autoantibody (ANA ≥1:80, RNP, SSA/SSB or any of the myositis-specific autoantibodies [e.g. anti-synthetase autoantibodies (anti-Jo-1, PL-7, PL-12, EJ, OJ), anti-SRP, anti-Mi-2, anti-p140 (also known as anti-MDA5), anti-p155/140 (also known as anti-TIF), anti-NXP-2 (also known as MJ)] were eligible for the study. Patients with a diagnosis of definite or probable PM were required to have at least one myositis-specific autoantibody. Patients with a diagnosis of definite or probable PM in the absence of myositis-specific autoantibodies were required to undergo adjudication of the diagnosis by a committee of three experts. Inclusion/exclusion criteria for the study are presented in Supplementary Table S1, available at Rheumatology online.
Refractory IIM was defined as chronic active IIM with a history of inadequate response or intolerance to 3 months of glucocorticoids and/or at least a history of inadequate response or intolerance to 3 months of one IS agent (azathioprine, methotrexate, mycophenolate mofetil, leflunomide, tacrolimus, ciclosporin, cyclophosphamide, rituximab or IVIG). To define active myositis, we used the core set measures (CSMs), a standard definition of myositis disease activity, validated by the International Myositis Assessment and Clinical Studies (IMACS) Group [12]. Manual muscle testing (MMT8) <125/150 was a major criterion and at least two other criteria of CSMs had to be met. CSMs are listed in the inclusion criteria section in Supplementary Table S1, available at Rheumatology online. To avoid including patients with significant damage or muscle atrophy from chronic disease, muscle biopsy or muscle MRI documenting active myositis within 4 months prior to enrolment was required for patients with a history of IIM >7 years.
Concurrent IS medications
The background prednisone dose had to be stable at ≤15 mg/day for at least 2 weeks prior to screening. An increase in the dose of oral prednisone was permitted for a disease flare during the first 8 weeks after randomization but had to be tapered to ≤25% of the baseline dose by week 12. If the dose of prednisone could not be tapered by week 12, the patient was considered a treatment failure. Any patient requiring an increase of glucocorticoid dose after week 8 for IIM disease activity was also considered a treatment failure. Tapering of the prednisone dose was not prespecified and was left on the investigator’s discretion.
During the enrolment and study period, the allowed IS agents were azathioprine, methotrexate, mycophenolate mofetil, tacrolimus and ciclosporin, but treatment could not be initiated <2 months prior to screening and the dose had to be maintained for at least 2 weeks prior to screening. Patients treated with cyclophosphamide or rituximab were eligible for enrolment only after 6 months or 12 months from the last dose of the drug, respectively. Use of IVIG was allowed during the course of the trial if it was initiated >2 months prior to the screening visit with no changes in dose or frequency.
Clinical assessments
Study assessments were performed at baseline (week 0) and weeks 8, 16, 24, 32, 40, 52 and 64 and included a physical exam, Myositis Disease Activity Assessment Tool, patient global assessment on a visual analogue scale (VAS), physician global assessment on a VAS, HAQ and laboratory parameters. Damage related to disease or treatment was scored according to the Myositis Damage Index (MDI) [12].
A validated definition of improvement (DOI) and total improvement score (TIS) [1, 12–14] were used to measure clinical response and were calculated at each study visit (definitions for DOI and TIS are provided in Supplementary Tables S2 and S3, available at Rheumatology online).
Flow cytometry
A baseline sample (D0 or W40) of blood from each patient before receiving belimumab served as a paired control for samples obtained at 6 months (24 weeks) and 15 months (60–64 weeks) after receiving belimumab. To evaluate changes in the number and percent of B cells and B cell subsets, both fresh and frozen peripheral blood mononuclear cells were stained with cocktails of antibodies including anti-CD3, anti-CD19, anti-CD27, anti-CD38, anti-CD24, anti-IgD, anti- IgM, anti-CD21, anti-CD20 with mitotracker Red (MTR) and Live Dead dyes. CD19+ B cells were gated after doublets and dead cells and T cells were excluded. B cell subsets are identified as plasmablasts (CD27hiCD38hi), switched memory (SM; CD27+IgD−), unswitched memory (USM; CD27+IgD+), DN (CD27−IgD−), naïve (CD27−IgD+MTR−CD24+), transitional T1 (CD27−IgD+MTR+CD24+CD38hi), transitional T2 (CD27−IgD+MTR+CD24+CD38int), transitional T3 (CD27−IgD+MTR+CD24+CD38lo) and activated naïve (Act.Naive; CD27−IgD+MTR+CD24−). Flow cytometry data were analysed in a blinded fashion. The list of antibodies used is presented in Supplementary Table S4, available at Rheumatology online. Baseline samples from patients were also compared with historical data from 13 healthy donors [15].
Endpoints
The primary endpoints were the proportions of patients reaching the DOI and TIS at week 40 in the belimumab vs placebo arms. The IMACS DOI was published, validated and used as endpoints in myositis therapeutic trials at the time this study was initiated. It is calculated based on changes in each of six IMACS CSMs as a change in three of any six of the CSMs improved by ≥20%, with no worsening by ≥25% in any two CSMs. Since this clinical trial launched, TIS has been accepted by the ACR and EULAR as primary endpoints in myositis therapeutic trials and the protocol was modified to include TIS as the primary endpoint. TIS uses the weighted absolute change in the same six CSMs.
Secondary endpoints included individual changes in CSMs at week 40, the proportion of patients reaching the DOI and TIS after completing the open-label phase at week 64, the percent change in the prednisone dose from baseline to weeks 40 or 64 weeks and safety profile throughout the study.
Statistical analysis
We planned to enrol 60 patients, with 30 in each of the treatment arms, accounting for a 15% attrition rate. This sample size was calculated for 80% power (two-sided chi-squared test, α + 0.05) based on the assumption of a 10% placebo response rate at week 40 and the difference of 35% in response rate between the investigational agent and placebo. However, we had significant difficulty with enrolment in this trial and could not accomplish the established target.
Descriptive statistics (means, s.d.s, medians, ranges, frequencies, proportions), unpaired t-test, Fisher’s exact test, two-way analysis of variance (ANOVA) and ANOVA Friedman tests were used to analyse categorical and continuous variables, respectively.
Primary analyses were performed using the intention-to-treat (ITT) method. Patients who received at least five infusions (completed 12 weeks) during the randomized phase of the study were considered evaluable and were included in the ITT analysis. Patients who were classified as treatment failures were permitted to continue with the trial protocol in their respective assigned groups according to the best medical judgement of the treating physician. Baseline demographics and clinical data are reported on all randomized and ITT patients.
Safety data were collected on all randomized patients in the form of adverse events (AEs), serious AEs (SAEs) and AEs of special interest (serious hypersensitivity reaction or infusion reactions, suicidality, malignancy, serious infections, progressive multifocal leukoencephalopathy, abnormal liver enzymes) and summarized using descriptive statistics for both treatment groups.
Results
Baseline characteristics
A total of 29 patients were screened and 19 patients were enrolled, 2 of whom withdrew consent before receiving the study drug. Of the 17 patients randomized to receive belimumab or placebo infusions, 2 patients, 1 from each arm, were lost to follow-up before week 12. Fifteen patients received at least five doses of belimumab or placebo and were included in the final ITT analysis. Fourteen patients (8/9 in the belimumab arm and 6/7 in the placebo arm) completed all 40 weeks of the randomized phase. Seven (7/9) patients from the belimumab arm and 5 (5/7) from the placebo arm completed the 24 weeks of open-label extension with IV belimumab. A flowchart of the patients’ distribution is shown in Fig. 1. Baseline characteristics for patients included in the ITT analysis (n = 15) are presented in Table 1 and for all randomized patients (n = 17) are presented in Supplementary Table S5, available at Rheumatology online.
Figure 1.
Patients’ distribution flowchart. *Patients received less than five required treatment infusions and were excluded from the primary efficacy analysis
Table 1.
Baseline demographic and clinical characteristics of patients included in the ITT analysis
| Characteristics | Belimumab (n = 9) | Placebo (n = 6) | Total (N = 15) |
|---|---|---|---|
| Age, years | |||
| Mean (s.d.) | 50.1(14) | 49.5 (11.7) | 49.9 (12.7) |
| Median (range) | 46 (29–65) | 49 (33–68) | 46 (29–68) |
| Gender, n (%) | |||
| Male | 3 (33.3) | 1 (16.7) | 4 (26.6) |
| Female | 6 (66.7) | 5 (83.3) | 11 (73.3) |
| Race, n (%) | |||
| African American | 6 (66.7) | 0 | 6 (40) |
| White | 3 (33.3) | 3 (50) | 6 (40) |
| Asian—Central/South Asian | 0 (0) | 2 (33.3) | 2 (13.3) |
| White—Arabic/North African | 0 (0) | 1 (16.7) | 1 (6.66) |
| Subtype of IIM, n (%) | |||
| DM | 2 (22.2) | 2 (33.3) | 4 (26.7) |
| PM | 7 (77.8) | 4 (66.7) | 13 (86.8) |
| Disease duration, years | |||
| Mean (s.d.) | 3.3 (3.1) | 5.3 (4.4) | 4.13 (3.66) |
| Median (range) | 2.0 (1–11) | 4 (1–13) | 2 (1–13) |
| Serological profile, n (%) | |||
| ANA and other MAA | 7 (77.8) | 5 (83.3) | 12 (80) |
| SSA/SSB | 4 (44.4) | 3 (50) | 7 (46.7) |
| MSA | 4 (44.4) | 4 (66.7) | 8 (53.3) |
| History of IS, n (%) | |||
| Failed ≤1 IS | 6 (66.7) | 1 (16.7) | 7 (46.7) |
| Failed >1 IS | 3 (33.3) | 5 (83.3) | 8 (53.3) |
| Baseline prednisone dose | |||
| Mean (s.d.), mg | 8.5 (7.12) | 5 (4.47) | 7.1 (6.26) |
| Patients on prednisone, n (%) | 6 (66.7) | 4 (66.7) | 10 (66.7) |
| Concurrent IS agents, n (%) | |||
| MTX, MMF or AZA | 7 (77.8) | 5 (83.3) | 12 (80) |
| IVIG | 3 (33.3) | 4 (66.7) | 9 (60) |
| Combination of IS and IVIG | 2 (22.2) | 3 (50) | 4 (26.7) |
| Disease characteristics, mean (s.d.) | |||
| Patient global assessment VAS (0–10) | 5.5 (1.6) | 7.1 (2.4) | 6.1 (2.1) |
| MD global assessment VAS (0–10) | 4.3 (1.8) | 5.3 (0.8) | 4.7 (1.6) |
| MMT (0–150) | 115 (6.7) | 115 (9.0) | 115 (7.4) |
| Muscle enzyme, CPK (U/L) | 2124.3 (1882) | 515 (623.8) | 1481 (1681) |
| Muscle activity score VAS (0–10) | 4.6 (1.9) | 5.0 (1.0) | 4.7 (1.6) |
| Extramuscular disease activity VAS (0–10) | 1.0 (1.7) | 1.5 (1.4) | 1.232 (1.6) |
| Cutaneous VAS (0–10) | 0.5 (0.1) | 0.3 (0.3) | 1.4 (2.2) |
| HAQ (0–3) | 1.3 (0.6) | 1.1 (0.5) | 1.2 (0.6) |
| MDI (0–10) | 1.0 (1.6) | 1.9 (2.2) | 1.4 (1.8) |
MAA: myositis-associated antibodies; MSA: myositis-specific antibodies (anti-Jo-1, anti-PL-7, anti-PL-12, anti-EJ, anti-OJ, anti-KS, anti-SPR, anti-Mi-2, NXP2 and anti-HMGCR).
Groups were balanced for age, diagnosis (PM vs DM), antibody profile and severity of muscle disease based on the MMT8. Four patients with PM had no myositis-specific antibodies and required adjudication of the diagnosis by the committee. Two of them had only ANAs and two had ANAs and SSA/SSB antibodies.
Study arms were less balanced for race: Blacks were represented only in the belimumab group. The placebo group had slightly longer disease duration and a higher number of failed IS drugs in the year preceding enrolment. Although overall IS use at study entry was similar between the groups, more patients in the placebo arm were on a combination of IS and IVIG during the study. While patients randomized to placebo had a higher index of damage, fewer patients in this group were on prednisone and the mean steroid dose in the placebo arm was lower at baseline.
Primary endpoints
The proportion of patients reaching the DOI by week 40 was higher in the belimumab arm [33.3% (3/9 patients)] compared with those on placebo [16.7% (1/6 patients)] [relative risk (RR) 0.5 (95% CI 0.08, 2.65), P = 0.60]. After completion of the open-label phase at week 64, two patients lost response, while an additional two patients attained the DOI in belimumab group and no patients originally assigned to placebo achieved the DOI; the difference between the two treatment groups remained not statistically significant [belimumab 33.3% vs placebo 0%; RR 0 (95% CI 0, 1.47), P = 0.23] (Fig. 2A, Supplementary Table S6, available at Rheumatology online).
Figure 2.
Distribution of responses in each arm at week 40 and week 64 over time. (A) Proportion of responders by the DOI, TIS ≥40 and TIS ≥60 at weeks 40 and 64. (B) TIS change of individual patients in the placebo arm (dashed line) and belimumab arm (solid line) and the mean TIS of patients on placebo (bold dashed line) and belimumab (bold solid line) over time (0–64 weeks)
Of patients in the belimumab group, 55.5% (5/9 patients) attained TIS ≥40 at week 40 and 44.7% (4/9 patients) reached TIS ≥40 at week 64. One-third of patients [33.3% (2/6 patients)] in the placebo arm attained moderate or major improvement by TIS at week 40, but no patients had any further alteration in their TIS at week 64 after crossing over to open-label belimumab at week 40. The differences between the treatment arms were not statistically significant at any of the time points [week 40: RR 0.6 (95% CI 0.16, 1.82), P = 0.61 and week 64: RR 0.75 (95% CI 0.19, 2.51), P = 0.99] (Fig. 2A, Supplementary Table S6, available at Rheumatology online). Only 2/15 patients in the study, both from the belimumab group, crossed the major response threshold at week 40 (TIS = 72.5) and sustained their major response to week 64. The mean TIS was similar between the two groups over the time (week 0–week 40); the change of TIS over time is shown in Fig. 2B. There was no difference observed in the change of each component of the CSMs between treatment arms.
Steroid-sparing effect
At baseline, almost 70% of patients in each arm (6/9 in the belimumab arm and 4/6 in the placebo arm) were on prednisone with a mean dose 8.5 mg and 5 mg. respectively Two patients in the belimumab group—one with PM and positive ANA and another with DM and positive ANA and SSA/SSB antibodies—required rescue steroids at week 8 and were not able to be tapered by week 12 to <25% above the baseline dose. This accounted for the wide mean prednisone dose distribution. As was predefined by the protocol, these patients were considered as treatment failure. At the time of randomization, one of the patients was not on prednisone and another was on 15 mg/day. Both were on background IS (one on mycophenolate and one on methotrexate). Acute muscle strength decline was the main reason for the increase in prednisone dose.
There were no patients that needed a prednisone dose increase after week 8 in either arm. No patients assigned to the placebo group received steroid rescue during the study. No steroid-sparing effect was observed by calculating either the absolute or relative prednisone dose change.
B cell phenotype
Flow cytometry was performed on paired samples from 10 patients, 7 of whom received belimumab for 64 weeks and 3 who received placebo for 40 weeks followed by belimumab for 24 weeks. Clinical characteristics, serum BAFF levels and responses to belimumab treatment of these patients are shown in Supplementary Table S7 and Supplementary Fig. S2, available at Rheumatology online.
At baseline, the percentage of B cells in the live lymphocyte population was 9.7 (s.d. 7.7). Compared with healthy controls previously reported by our group [15], patients with myositis had a trend towards an increase in the percentage of naive B cells and a decrease in the percentage of memory B cells at baseline (Supplementary Fig. S3, available at Rheumatology online).
After treatment with belimumab, there was no significant reduction in the absolute B cell count at 24, 40 or 64 weeks compared with the pre-treatment levels (Fig. 3A and Table 2). However, there was a shift in the distribution of B cell subsets, with a significant reduction in the percentages of naïve B cells and significant increases in the percentages of switched memory B cells at both 40 and 64 weeks (Fig. 3B–D and Table 2). The absolute number of naïve B cells was significantly decreased at week 64 and the number of switched memory B cells was significantly increased at 40 weeks with a reversion to baseline by 64 weeks. There were no significant changes in the numbers of transitional B cells, unswitched memory cells, double negative B cells, activated naïve B cells, plasmablasts or CD3 T cells after treatment (Table 2 and Supplementary Fig. S4, available at Rheumatology online).
Figure 3.
B cell counts and subset distribution before and after belimumab treatment. (A) Percent (left) and number (right) of B cells in peripheral blood of IIM patients before (D0) and 40 weeks (W40) and 64 weeks (W64) after belimumab treatment (n = 7). Individual patients are colour coded. (B) Representative tNSE plots of one patient show the distribution of B cell subsets before (left) and after (right) treatment. Percent (left) and number (right) of (C) naïve and (D) switched memory B cells in peripheral blood of IIM patients as in (A). ANOVA Friedman test with Dunn’s multiple comparisons. *P < 0.05, **P < 0.005, ns = P not significant. tNSE: t-distributed neighbor embedding
Table 2.
Absolute B cell count at 24, 40 or 64 weeks compared with the pretreatment levels.
| Cell population | D0 | Week 24 | Week 40 | Week 60 |
|---|---|---|---|---|
| CD19+ | ||||
| % (s.d.)a | 9.7 (7.7) | 10.9 (7.7) | 5.3 (3.7) | 4.3 (2.9) |
| n/µl (s.d.) | 143.4 (140.8) | 131.4 (113.9) | 148.8 (192.3) | 77.0 (89.1) |
| T1b | ||||
| % (s.d.) | 0.8 (1.4) | 1.3 (1.1) | 3.0 (5.2) | 2.5 (3.7) |
| n/µl (s.d.) | 0.4 (0.9) | 2.0 (2.4) | 0.8 (0.9) | 0.7 (0.8) |
| T2b | ||||
| % (s.d.) | 2.7 (3.0) | 5.7 (5.5) | 3.2 (3.7) | 3.0 (3.2) |
| n/µl (s.d.) | 2.3 (3.5) | 11.1 (16.4) | 1.1 (0.7) | 1.1 (1.3) |
| T3b | ||||
| % (s.d.) | 6.7 (7.4) | 22.3 (16.5) | 8.2 (5.7) | 6.5 (4.2) |
| n/µl (s.d.) | 6.4 (6.1) | 31.8 (35.7) | 6.5 (5.8) | 3.8 (4.7) |
| MTG+CD24+CD38−b | ||||
| Count, % (s.d.) | 1.4 (1.6) | 2.8 (2.6) | 1.9 (1.2) | 2.9 (1.4) |
| Count, n/µl (s.d.) | 1.5 (1.5) | 1.9 (1.8) | 2.9 (4.2) | 2.0 (2.5) |
| Naïveb, % (s.d.) | 65.6 (19.4) | 22.9 (7.2) | 34.2 (22.5) | 34.2 (26.8) |
| Naïveb, n/µl (s.d.) | 109.9 (29.7) | 35.5 (40.0) | 83.8 (134.3) | 41.9 (66.4) |
| Activated naïveb | ||||
| % (s.d.) | 4.5 (5.0) | 6.1 (8.4) | 1.5 (1.7) | 2.6 (3.4) |
| n/µl (s.d.) | 3.6 (4.7) | 14.3 (23.3) | 1.4 (1.5) | 1.5 (1.7) |
| DNb | ||||
| % (s.d.) | 7.0 (6.5) | 9.8 (11.2) | 10.8 (8.4) | 18.8 (9.7) |
| n/µl (s.d.) | 7.6 (8.9) | 10.3 (8.1) | 8.8 (6.9) | 12.1 (12.6) |
| Unswitched memoryb | ||||
| % (s.d.) | 4.0 (6.1) | 7.7 (6.3) | 10.7 (9.5) | 5.3 (4.3) |
| n/µl (s.d.) | 3.9 (5.1) | 5.3 (3.7) | 11.7 (12.4) | 2.1 (2.2) |
| Switched memoryb | ||||
| % (s.d.) | 5.9 (4.4) | 20.9 (12.9) | 24.4 (14.4) | 20.2 (17.4) |
| n/µl (s.d.) | 6.7 (7.0) | 18.4 (4.9) | 29.7 (31.0) | 10.0 (10.3) |
| Plasmablasts (PB)a | ||||
| % (s.d.) | 0.1 (0.1) | 0.1 (0.0) | 0.1 (0.3) | 0.2 (0.3) |
| n/µl (s.d.) | 0.002 (0.001) | 0.001 (0.001) | 0.001 (0.002) | 0.002 (0.002) |
% in lymphocytes.
% in B cells.
Adverse Events
Safety data were analysed on all 17 randomized patients. A total of 45 AEs were observed through both phases of the trial (32 occurred during the randomized phase and 13 during the open-label phase). There were 17 events reported in the belimumab arm and 15 events in the placebo arm during the randomized phase. Multiple events were reported per patient. Two patients terminated the study before receiving five doses of belimumab. One early termination occurred in the belimumab arm at week 12 due to a perforated appendix with a complicated postoperative course. This event was classified as an SAE and one patient was terminated at week 4 due to incarceration.
Eleven infections were observed through the course of the trial. Seven events were recorded as mild respiratory infections during the randomized phase (two in belimumab arm and five in the placebo arm) and one mild respiratory infection in the open-label phase. One urinary tract infection was observed in the placebo arm during the randomization phase. Three additional infection events were recorded in the open-label phase: one respiratory, one urinary tract and one Candida esophagitis; all were considered mild.
One patient in the belimumab arm, during the randomization phase, developed an exacerbation of an adjustment disorder, determined not to be related to the drug: this patient continued in the study to the end of the open-label phase with no interruption of drug administration (Table 3).
Table 3.
Incidence of SAEs and AEs
| Characteristics | Randomized phase |
Open-label phase |
|
|---|---|---|---|
| Belimumab | Placebo | Belimumab | |
| Patients with an AE. % (n/N) | 60 (6/10) | 85 (6/7) | 42.9 (6/14) |
| Events, n | 17 | 15 | 13 |
| SAEs, n | 1 perforated appendixa | 0 | 0 |
| AEs of interest | |||
| Infections, n | |||
| Respiratory | 2 (1 influenza) | 5 (1 coronavirus) | 1 |
| Urinary tract | 0 | 1 | 1c |
| Candida esophagitis | 0 | 0 | 1 |
| Adjustment disorder, n | 1 | 0 | 0 |
| Transaminitis, n | 1 | 0 | 0 |
| Other side effects, n | |||
| Myalgia and arthralgia | 4b | 0 | 0 |
| Fatigue/somnolence | 0 | 3b | 0 |
| Light-headedness | 0 | 2b | 0 |
| Insomnia | 0 | 0 | 1 |
| Headache | 0 | 1 | 0 |
| Rash | 1 | 0 | 2 (1 pruritus and 1 rash at site of infusion) |
| Gout flare | 2b | 0 | 2b |
| Diabetes mellitus | 0 | 0 | 1 |
| Leg swelling | 1 | 0 | 1 |
| Heartburn/gastroesophageal reflux disease | 1 | 1 | 0 |
| Hyperlipidaemia | 0 | 0 | 1 |
| Other | 3 | 2 | 2 |
Event led to discontinuation of the drug and termination of participation in the study.
Multiple events per one patient.
Infection occurred after urethroplasty.
Discussion
Current treatment of IIM consists of combinations of glucocorticoids, IVIG (recently US Food and Drug Administration–approved Octagam) [16] and various IS agents, such as methotrexate, mycophenolic acid, azathioprine and tacrolimus. B cell targeting therapies are used in refractory cases despite inconclusive results from a large clinical trial of rituximab in IIM [1]. Recent observations suggest the potential importance of the BAFF pathway in the pathogenesis of IIM [6–10]. We report here the first proof-of-concept study in patients with refractory IIM that investigated the safety and efficacy of belimumab, a monoclonal antibody that inhibits BAFF, in addition to the SoC for the treatment of refractory IIM.
We did not observe statistical differences in the clinical response of patients randomized to belimumab compared with placebo at any time points. A higher proportion of patients in the belimumab group attained at least moderate response and two patients had major responses of TIS ≥60 by week 24, which were sustained until the end of the study. A high response rate was also observed in the placebo arm: all patients had at least minimal improvement and one-third of the patients had a moderate–major response by week 40. No patients in the placebo group reached a major TIS ≥60, nor was there a gain in TIS in the placebo group after switching to the open-label belimumab phase. These observations suggest that greater discrimination of responses might be detected with more stringent response criteria such as TIS ≥60. Treatment failures, requiring an increase in prednisone dose, were only observed in the belimumab group. These occurred early, at week 8 of the study, well before a response to belimumab is expected and contributed to our inability to detect a steroid-sparing effect.
B cell phenotyping of patients with myositis has been limited and interpretation of results may be challenging because of the concomitant use of IS drugs. Previous studies of patients with DM/PM have observed an increase in the percentages of naïve B cells and a decrease in the percentages of memory B cells in the peripheral blood [17–19], similar to what we report here. This higher ratio of naïve to memory B cells could be due to higher levels of BAFF in myositis subjects compared with healthy controls that normalizes upon treatment. While Piper et al. [20] demonstrated an increase in immature transitional B cells in active untreated juvenile DM, we did not observe an increase in transitional B cells, likely confounded by the fact that our patients were heavily pretreated with immunosuppression.
Clinical responses to belimumab have been described in patients with SLE as early as 3 months after treatment initiation, with early loss of naïve and activated naïve B cells and a slower loss of other B cell subsets [21]. Switched memory B cells are resistant to belimumab treatment [15, 21–24] and there are conflicting reports about the effect of belimumab on plasma cells [15, 21, 23–25]. In the patients with myositis reported here, belimumab treatment did not deplete B cells but conferred the expected alteration in B cell phenotype with a decrease in naïve B cell frequency and number and an increase in switched memory B cells. However, while the expected biological effect of belimumab on B cell subset distribution was observed, the degree of B cell count changes was not predictive of response and did not correlate with the early and sustained major responses seen in the two patients from the belimumab arm.
Belimumab treatment was well tolerated and no new safety signals were observed during this study. Serious and non-serious infections were balanced between the treatment groups. One patient in the belimumab arm had an adjustment disorder exacerbation, determined not to be belimumab related, and the drug was continued with no interruption. The only SAE was observed after week 12 was in the belimumab arm; the patient had a perforated appendix and was terminated from the study.
The major limitations of this study were the small sample size and a higher-than-expected placebo response that reduced the power for the primary outcome analysis and did not allow for analysis of disease subsets. Based on the observed effect size of 20% in the difference of TIS ≥40 at week 40 between the belimumab and placebo arms, the number of subjects would need to be 158 (79 per each arm) to achieve 80% power.
The use of multiple background IS therapy in our study is likely a major confounding factor in the higher-than-expected placebo response rate. IS therapies are reported to affect the phenotypes of peripheral blood lymphocytes and cytokine production in IIM [26]. Furthermore, while steroids and hydroxychloroquine lower BAFF levels, other ISs may lead to BAFF excess, salvaging self-reactive B cells and therefore weakening the degree of response to belimumab [27–29]. Most patients in this trial were on background IS agents, with almost half of them failing multiple IS medications prior to enrolment (83% of patients in the placebo arm and 33% of patients in the belimumab arm). In addition, more patients in the placebo arm were on IVIG compared with the belimumab arm (67% in the placebo arm vs 33% in the belimumab arm) and a combination of IVIG with IS (50% in the placebo arm vs 22% in the belimumab arm). The use of multiple background IS medications could have decreased our ability to detect a clinical effect of belimumab.
In conclusion, the administration of belimumab to patients with refractory IIM on SoC therapy did not result in a statistically significant improvement in disease activity. However, greater proportions of patients on belimumab achieved the DOI and had attained at least a moderate TIS ≥40 or a major TIS ≥60. No steroid-sparing effect was detected. No new safety signals were identified. Modest biological effects of belimumab on B cell subsets occurred, but these changes did not correlate with clinical response. This pilot clinical trial provided valuable information that could contribute to the design of clinical trials in IIM with the use of more stringent response criteria. Furthermore, planning to target patients with early disease and on less background IS therapy may improve the effect size and power of future studies.
Supplementary Material
Contributor Information
Galina Marder, Division of Rheumatology, Northwell Health, Donald and Barbara Zucker School of Medicine, Great Neck, NY, USA.
Tam Quach, Institute of Molecular Medicine, Feinstein Institutes for Medical Research, Northwell Health, Manhasset, NY, USA.
Priyal Chadha, Division of Rheumatology, Northwell Health, Donald and Barbara Zucker School of Medicine, Great Neck, NY, USA.
Preeya Nandkumar, Division of Rheumatology, Northwell Health, Donald and Barbara Zucker School of Medicine, Great Neck, NY, USA.
Jimmy Tsang, Institute of Molecular Medicine, Feinstein Institutes for Medical Research, Northwell Health, Manhasset, NY, USA.
Todd Levine, Phoenix Neurological Associates, Phoenix, AZ, USA.
Elena Schiopu, Division of Rheumatology, University of Michigan, Ann Arbor, MI, USA.
Richard Furie, Division of Rheumatology, Northwell Health, Donald and Barbara Zucker School of Medicine, Great Neck, NY, USA.
Anne Davidson, Division of Rheumatology, Northwell Health, Donald and Barbara Zucker School of Medicine, Great Neck, NY, USA; Institute of Molecular Medicine, Feinstein Institutes for Medical Research, Northwell Health, Manhasset, NY, USA.
Sonali Narain, Division of Rheumatology, Northwell Health, Donald and Barbara Zucker School of Medicine, Great Neck, NY, USA.
Supplementary material
Supplementary material is available at Rheumatology online.
Data availability
The data underlying this article are available in the article and in its online supplementary material.
Funding
Funding was received from a GlaxoSmithKline research grant and the National Institutes of Health (NIH1R21AR070540-01 and K01 AR075097).
Disclosure statement: G.M. received a GlaxoSmithKline research grant. R.F. has received consultant and research support from GlaxoSmithKline. The remaining authors have declared no conflicts of interest.
References
- 1. Oddis CV, Reed AM, Aggarwal R. et al. Rituximab in the treatment of refractory adult and juvenile dermatomyositis and adult polymyositis: a randomized, placebo-phase trial. Arthritis Rheum 2013;65:314–24. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Levine TD. Rituximab in the treatment of dermatomyositis: an open-label pilot study. Arthritis Rheum 2005;52:601–7. [DOI] [PubMed] [Google Scholar]
- 3. Chung L, Genovese MC, Fiorentino DF.. A pilot trial of rituximab in the treatment of patients with dermatomyositis. Arch Dermatol 2007;143:763–7. [DOI] [PubMed] [Google Scholar]
- 4. Valiyil R, Casciola-Rosen L, Hong G. et al. Rituximab therapy for myopathy associated with anti-signal recognition particle antibodies: a case series. Arthritis Care Res (Hoboken) 2010;62:1328–34. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Mahler EA, Blom M, Voermans NC. et al. Rituximab treatment in patients with refractory inflammatory myopathies. Rheumatology (Oxford) 2011;50:2206–13. [DOI] [PubMed] [Google Scholar]
- 6. Salajegheh M, Pinkus JL, Amato AA. et al. Permissive environment for B‐cell maturation in myositis muscle in the absence of B‐cell follicles. Muscle Nerve 2010;42:576–83. [DOI] [PubMed] [Google Scholar]
- 7. Kryštůfková O, Vallerskog T, Helmers SB. et al. Increased serum levels of B cell activating factor (BAFF) in subsets of patients with idiopathic inflammatory myopathies. Ann Rheum Dis 2009;68:836–43. [DOI] [PubMed] [Google Scholar]
- 8. Kryštůfková O, Hulejová H, Mann HF. et al. Serum levels of B-cell activating factor of the TNF family (BAFF) correlate with anti-Jo-1 autoantibodies levels and disease activity in patients with anti-Jo-1positive polymyositis and dermatomyositis. Arthritis Res Ther 2018;20:158. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9. Kryštůfková O, Helmers SB, Venalis P. et al. Expression of BAFF receptors in muscle tissue of myositis patients with anti-Jo-1 or anti-Ro52/anti-Ro60 autoantibodies. Arthritis Res Ther 2014;16:454. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10. Baek A, Park HJ, Na SJ. et al. The expression of BAFF in the muscles of patients with dermatomyositis. J Neuroimmunol 2012;249:96–100. [DOI] [PubMed] [Google Scholar]
- 11. Zhao Y, Zhang W, Liu Y, Wang Z, Yuan Y.. Factors associated with refractory autoimmune necrotizing myopathy with anti-signal recognition particle antibodies. Orphanet J Rare Dis 2020;15:181. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Rider LG, Werth VP, Huber AM. et al. Measures of adult and juvenile dermatomyositis, polymyositis, and inclusion body myositis: physician and Patient/Parent Global Activity, Manual Muscle Testing (MMT), Health Assessment Questionnaire (HAQ)/Childhood Health Assessment Questionnaire (C-HAQ), Childhood Myositis Assessment Scale (CMAS), Myositis Disease Activity Assessment Tool (MDAAT), Disease Activity Score (DAS), Short Form 36 (SF-36), Child Health Questionnaire (CHQ), physician global damage, Myositis Damage Index (MDI), Quantitative Muscle Testing (QMT), Myositis Functional Index-2 (FI-2), Myositis Activities Profile (MAP), Inclusion Body Myositis Functional Rating Scale (IBMFRS), Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI), Cutaneous Assessment Tool (CAT), Dermatomyositis Skin Severity Index (DSSI), Skindex, and Dermatology Life Quality Index (DLQI). Arthritis Care Res (Hoboken) 2011;63(Suppl 11):S118–57. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13. Rider LG, Giannini EH, Brunner HI. et al. International consensus on preliminary definitions of improvement in adult and juvenile myositis. Arthritis Rheum 2004;50:2281–90. [DOI] [PubMed] [Google Scholar]
- 14. Aggarwal R, Rider LG, Ruperto N. et al. 2016 American College of Rheumatology/European League Against Rheumatism Criteria for minimal, moderate, and major clinical response in adult dermatomyositis and polymyositis: an international myositis assessment and clinical studies. Ann Rheum Dis 2017;76:792–801. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15. Huang W, Quach TD, Dascalu C. et al. Belimumab promotes negative selection of activated autoreactive B cells in systemic lupus erythematosus patients. JCI Insight 2018;3:e122525. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16. Aggarwal R, Charles-Schoeman C, Schessl J. et al. Trial of intravenous immune globulin in dermatomyositis. N Engl J Med 2022;387:1264–78. [DOI] [PubMed] [Google Scholar]
- 17. Ishii W, Matsuda M, Shimojima Y. et al. Flow cytometric analysis of lymphocyte subpopulations and TH1/TH2 balance in patients with polymyositis and dermatomyositis. Intern Med 2008;47:1593–9. [DOI] [PubMed] [Google Scholar]
- 18. Dzangué-Tchoupou G, Allenbach Y, Preuße C. et al. Mass cytometry reveals an impairment of B cell homeostasis in anti-synthetase syndrome. J Neuroimmunol 2019;332:212–5. [DOI] [PubMed] [Google Scholar]
- 19. Wilfong EM, Bartkowiak T, Vowell KN. et al. High-dimensional analysis reveals distinct endotypes in patients with idiopathic inflammatory myopathies. Front Immunol 2022;13:756018. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20. Piper CJM, Wilkinson MGL, Deakin CT. et al. CD19+CD24hiCD38hi B cells are expanded in juvenile dermatomyositis and exhibit a pro-inflammatory phenotype after activation through toll-like receptor 7 and interferon-α. Front Immunol 2018;9:1372. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. Ramsköld D, Parodis I, Lakshmikanth T. et al. B cell alterations during BAFF inhibition with belimumab in SLE. EBioMedicine 2019;40:517–27. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22. Brooks JF, Zikherman J.. The BAFFling persistence of memory B cells. J Exp Med 2021;218:e20202057. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23. Parodis I, Gomez A, Lindblom J. et al. Early changes in B and plasma cell subsets and traditional serological markers as predictors of SRI-4 response to therapy in systemic lupus erythematosus. Front Med (Lausanne) 2022;9:852162. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24. Stohl W, Hiepe F, Latinis KM. et al. Belimumab reduces autoantibodies, normalizes low complement levels, and reduces select B cell populations in patients with systemic lupus erythematosus. Arthritis Rheum 2012;64:2328–37. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25. Jacobi AM, Huang W, Wang T. et al. Effect of long-term belimumab treatment on B cells in systemic lupus erythematosus: extension of a phase II, double-blind, placebo-controlled, dose-ranging study. Arthritis Rheum 2010;62:201–10. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 26. Shimojima Y, Ishii W, Matsuda M. et al. Phenotypes of peripheral blood lymphocytes and cytokine expression in polymyositis and dermatomyositis before treatment and after clinical remission. Clin Med Insights Arthritis Musculoskelet Disord 2012;5:77–87. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27. Hernández-Breijo B, Gomez A, Soukka S, Johansson P, Parodis I.. Antimalarial agents diminish while methotrexate, azathioprine, and mycophenolic acid increase BAFF levels in systemic lupus erythematosus. Autoimmun Rev 2019;18:102372. [DOI] [PubMed] [Google Scholar]
- 28. Thien M, Phan TG, Gardam S. et al. Excess BAFF rescues self-reactive B cells from peripheral deletion and allows them to enter forbidden follicular and marginal zone niches. Immunity 2004;20:785–98. [DOI] [PubMed] [Google Scholar]
- 29. Cepika AM, Soldo Jureša D, Morović Vergles J. et al. Decrease in circulating DNA, IL-10 and BAFF levels in newly diagnosed SLE patients after corticosteroid and chloroquine treatment. Cell Immunol 2012;276:196–203. [DOI] [PubMed] [Google Scholar]
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Data Availability Statement
The data underlying this article are available in the article and in its online supplementary material.