A phase 1b clinical trial evaluating sifalimumab, an anti-IFN-α monoclonal antibody, shows target neutralisation of a type I IFN signature in blood of dermatomyositis and polymyositis patients

Abstract

Objective: To assess the pharmacodynamic effects of sifalimumab, an investigational anti-IFN-α monoclonal antibody, in the blood and muscle of adult dermatomyositis and polymyositis patients by measuring neutralisation of a type I IFN gene signature (IFNGS) following drug exposure.

Methods: A phase 1b randomised, double-blinded, placebo controlled, dose-escalation, multicentre clinical trial was conducted to evaluate sifalimumab in dermatomyositis or polymyositis patients. Blood and muscle biopsies were procured before and after sifalimumab administration. Selected proteins were measured in patient serum with a multiplex assay, in the muscle using immunohistochemistry, and transcripts were profiled with microarray and quantitative reverse transcriptase PCR assays. A 13-gene IFNGS was used to measure the pharmacological effect of sifalimumab.

Results: The IFNGS was suppressed by a median of 53-66% across three time points (days 28, 56 and 98) in blood (p=0.019) and 47% at day 98 in muscle specimens post-sifalimumab administration. Both IFN-inducible transcripts and proteins were prevalently suppressed following sifalimumab administration. Patients with 15% or greater improvement from baseline manual muscle testing scores showed greater neutralisation of the IFNGS than patients with less than 15% improvement in both blood and muscle. Pathway/functional analysis of transcripts suppressed by sifalimumab showed that leucocyte infiltration, antigen presentation and immunoglobulin categories were most suppressed by sifalimumab and highly correlated with IFNGS neutralisation in muscle.

Conclusions: Sifalimumab suppressed the IFNGS in blood and muscle tissue in myositis patients, consistent with this molecule's mechanism of action with a positive correlative trend between target neutralisation and clinical improvement. These observations will require confirmation in a larger trial powered to evaluate efficacy.

Trial registration: ClinicalTrials.gov NCT00533091.

Keywords: Cytokines; Dermatomyositis; Polymyositis.

Figure 1

Median target neutralisation (with median absolute deviation error bars) of the IFN gene signature (IFNGS) as calculated based on the expression of 13 genes (see supplementary material, available online only) pre-dose and post-dose up to day 98 for dose cohorts of 0.3 mg/kg (green), 1 mg/kg (blue), 3 mg/kg (orange), 10 mg/kg (purple) and placebo (red) in (A) blood and (C) muscle specimens, as well as median combined dose cohorts (blue) versus placebo treatment cohorts (red) in (B) blood and (D) muscle specimens from dermatomyositis or polymyositis patients. The y-axis represents the percentage of IFNGS remaining following treatment; each line is the median of the respective dose cohort. p Values at each time point for each dose cohort are provided in supplementary material (available online only), while those with p<0.05 are marked with an asterisk.

Figure 2

Target neutralisation of the IFN gene signature (IFNGS) calculated at days 28 (n=36), 56 (n=31) and 98 (n=32) post-treatment in blood specimens (first three columns) and day 98 (n=30) post-treatment in muscle specimens (last column) with either sifalimumab (blue vertical bar) or placebo (green vertical bar) on a patient level (designated on the right y-axis). Each row indicates a patient with values approaching red, representing maximum neutralisation of the IFNGS and values approaching blue, representing minimum neutralisation. Both blood and muscle comparisons are made to day 0 (pre-treatment) and all columns are sorted based on the day 28 column values. Neutralisation values in black indicate missing data points.

Figure 3

Stratified target neutralisation curves representing the proportion of dermatomyositis (n=14) or polymyositis (n=10) patients dosed with sifalimumab who demonstrate neutralisation of their IFN gene signature (IFNGS) at day 98 at the provided threshold value on the x-axis in (A) blood and (B) muscle specimens. Plots include all IFNGS-positive patients. Patients who exhibited a 15% or greater improvement in MMT8 score at day 98 (compared to day 0) are represented by the blue lines (blood n=8; muscle n=7), while those patients who did not are represented by the purple lines (blood n=16; muscle n=17).

Figure 4

Three of the pathways most suppressed by sifalimumab at day 98 in muscle specimens from dermatomyositis or polymyositis patients and unique to type I IFN signalling. Each point indicates a gene in either the (A) leucocyte extravasation pathway, (B) antigen presentation pathway, or (C) B-cell development pathway treated with either sifalimumab (blue squares) or placebo (red triangles). The y-axis represents the percentage of patients with at least 37.5% neutralisation of pathway-enricheds transcripts at day 98 in muscle tissue specimens.

Figure 5

Correlation between target neutralisation of the IFN gene signature (IFNGS) and neutralisation of the (A) leucocyte index, (B) MHC class I signature and (C) immunoglobulin signature in dermatomyositis (DM; red squares) or polymyositis (PM; blue circles) patient muscle specimens. Red dashed lines flanking the black dotted least squares fit line indicate 95% CI. The plots indicate that the alterations of the three gene signatures display significant negative correlation with target neutralisation of the IFNGS in muscle.