Sample stability and variability of B-cell subsets in blood from healthy subjects and patients with systemic lupus erythematosus

Immune phenotyping in a pediatric multicenter transplant study: Suitability of a preformulated dry-antibody panel system

Flow-cytometric immune phenotyping is influenced by cryopreservation and inter-laboratory variability limiting comparability in multicenter studies. We assessed a system of optimized, pre-mixed dry-antibody panel tubes requiring small amounts of whole blood for validity, reliability and challenges in a Canadian multicenter study (POSITIVE) with long-distance sample shipping, using standardized protocols. Thirty-seven children awaiting solid-organ transplant were enrolled for parallel immune-phenotyping with both validated, optimized in-house panels and the dry-antibody system. Samples were collected before, 3 and 12 months post-transplant. Quality-assurance measures and congruence of phenotypes were compared using Bland-Altman comparisons, linear regression and group comparisons. Samples showed excellent lymphocyte viability (mean 94.8 %) and recovery when processed within 30 h. Comparing staining methods, significant correlations (Spearman correlation coefficient >0.6, p < 0.05), mean difference <5 % and variation 2SD <25 % were found for natural-killer, T and B cells, including many immunologically important cell subsets (CD8+, naïve, memory CD4+ T; switched-memory, transitional B). Some subgroups (plasmablasts, CD1d+CD5hi B cells) showed weak correlations, limiting interpretation reliability. The dry-antibody system provides a reliable method for standardized analysis of many immune phenotypes after long-distance shipping when processed within 30 h, rendering the system attractive for pediatric studies due to small blood amounts required and highly standardized processing and analysis.

Blisibimod for treatment of systemic lupus erythematosus: with trials you become wiser

INTRODUCTION

Blisibimod is a potent and selective inhibitor of B cell activating factor (BAFF), a mediator of differentiation, maturation and survival of B cells. It has a unique tetravalent, 'peptibody' structure and resulting high potency, and is currently in clinical evaluation for the treatment of SLE. The importance of BAFF in the pathogenesis of systemic lupus erythematosus (SLE) is under intense investigation. The anti BAFF monoclonal antibody belimumab was approved by the FDA for the treatment of SLE.

AREAS COVERED

The general properties of blisibimod are reviewed including pharmacokinetic and pharmacodynamic properties in patients with SLE, efficacy and safety in the phase 2 PEARL-SC and open-label extension trials, and the focus in the ongoing phase 3 trial (CHABLIS-SC1) on the hypothesized 'responder' population. In addition, the rationale for evaluating blisibimod in patients with IgA nephropathy, a common nephritic disease for which there is no approved therapy, is presented.

EXPERT OPINION

Blisibimod's unique tetravalent, peptibody structure and resulting high potency, and the deliberate focus of the Phase 3 clinical development program on the 'responder populations' identified in completed trials in SLE raise the possibility that blisibimod will become an important medication for treatment of SLE and IgA nephropathy.

Treatment of systemic lupus erythematosus patients with the BAFF antagonist "peptibody" blisibimod (AMG 623/A-623): results from randomized, double-blind phase 1a and phase 1b trials

INTRODUCTION

Blisibimod is a potent B cell-activating factor (BAFF) antagonist that binds to both cell membrane-expressed and soluble BAFF. The goal of these first-in-human studies was to characterize the safety, tolerability, and pharmacokinetic and pharmacodynamic profiles of blisibimod in subjects with systemic lupus erythematosus (SLE).

METHODS

SLE subjects with mild disease that was stable/inactive at baseline received either a single dose of blisibimod (0.1, 0.3, 1, or 3 mg/kg subcutaneous [SC] or 1, 3, or 6 mg/kg intravenous [IV]) or placebo (phase 1a; N = 54), or four weekly doses of blisibimod (0.3, 1, or 3 mg/kg SC or 6 mg/kg IV) or placebo (phase 1b; N = 63). Safety and tolerability measures were collected, and B cell subset measurements and pharmacokinetic analyses were performed.

RESULTS

All subjects (93 % female; mean age 43.7 years) carried the diagnosis of SLE for ≥ 1 year. Single- and multiple-dose treatment with blisibimod produced a decrease in the number of naïve B cells (24-76 %) and a transient relative increase in the memory B cell compartment, with the greatest effect on IgD(-)CD27+; there were no notable changes in T cells or natural killer cells. With time, memory B cells reverted to baseline, leading to a calculated 30 % reduction in total B cells by approximately 160 days after the first dose. In both the single- and multiple-dosing SC cohorts, the pharmacokinetic profile indicated slow absorption, dose-proportional exposure from 0.3 through 3.0 mg/kg SC and 1 through 6 mg/kg IV, linear pharmacokinetics across the dose range of 1.0-6.0 mg/kg, and accumulation ratios ranging from 2.21 to 2.76. The relative increase in memory B cells was not associated with safety signals, and the incidence of adverse events, anti-blisibimod antibodies, and clinical laboratory abnormalities were comparable between blisibimod- and placebo-treated subjects.

CONCLUSIONS

Blisibimod changed the constituency of the B cell pool and single and multiple doses of blisibimod exhibited approximate dose-proportional pharmacokinetics across the dose range 1.0-6.0 mg/kg. The safety and tolerability profile of blisibimod in SLE was comparable with that of placebo. These findings support further studies of blisibimod in SLE and other B cell-mediated diseases.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02443506 . Registered 11 May 2015. NCT02411136 Registered 7 April 2015.