Repeated 5-day cycles of low dose aldesleukin in amyotrophic lateral sclerosis (IMODALS): A phase 2a randomised, double-blind, placebo-controlled trial

Abstract

Background: Low-dose interleukin-2 (ld-IL-2) enhances regulatory T-cell (Treg) function in auto-inflammatory conditions. Neuroinflammation being a pathogenic feature of amyotrophic lateral sclerosis (ALS), we evaluated the pharmacodynamics and safety of ld-IL-2 in ALS subjects.

Methods: We performed a single centre, parallel three-arm, randomised, double-blind, placebo-controlled study. Eligibility criteria included age < 75 years, disease duration < 5 years, riluzole treatment > 3 months, and a slow vital capacity ≥ 70% of normal. Patients were randomised (1:1:1) to aldesleukin 2 MIU, 1 MIU, or placebo once daily for 5 days every 4 weeks for 3 cycles. Primary outcome was change from baseline in Treg percentage of CD4⁺ T cells (%Tregs) following a first cycle. Secondary laboratory outcomes included: %Treg and Treg number following repeated cycles, and plasma CCL2 and neurofilament light chain protein (NFL) concentrations as surrogate markers of efficacy. Safety outcomes included motor-function (ALSFRS-R), slow vital capacity (SVC), and adverse event reports. This trial is registered with ClinicalTrials.gov, NCT02059759.

Findings: All randomised patients (12 per group), recruited from October 2015 to December 2015, were alive at the end of follow-up and included in the intent-to-treat (ITT) analysis. No drug-related serious adverse event was observed. Non-serious adverse events occurred more frequently with the 1 and 2 MIU IL-2 doses compared to placebo, including injection site reactions and flu-like symptoms. Primary outcome analysis showed a significant increase (p < 0·0001) in %Tregs in the 2 MIU and 1 MIU arms (mean [SD]: 2 MIU: +6·2% [2·2]; 1 MIU: +3·9% [1·2]) as compared to placebo (mean [SD]: -0·49% [1·3]). Effect sizes (ES) were large in treated groups: 2 MIU ES=3·7 (IC95%: 2·3-4·9) and 1 MIU ES=3·5 (IC95%: 2·1-4·6). Secondary outcomes showed a significant increase in %Tregs following repeated cycles (p < 0·0001) as compared to placebo, and a dose-dependent decrease in plasma CCL2 (p = 0·0049). There were no significant differences amongst the three groups on plasma NFL levels.

Interpretation: Ld-IL-2 is well tolerated and immunologically effective in subjects with ALS. These results warrant further investigation into their eventual therapeutic impact on slowing ALS disease progression.

Funding: The French Health Ministry (PHRC-I-14-056), EU H2020 (grant #633413), and the Association pour la Recherche sur la SLA (ARSLA).

Keywords: Amyotrophic lateral sclerosis; Biomarkers; Low dose interleukin-2; Neuro-inflammation; Randomised clinical trial; Regulatory T cells.

Fig. 1.

Trial profile. ALSFRS-R: Amyotrophic Lateral Sclerosis Functional Rating Score – Revised; BT: Routine blood tests (see supplementary methods for detail); Cyt: Fresh Blood Cytometry (see supplementary methods for detail); SVC: slow vital capacity; PBMCs: Peripheral Blood Mononuclear Cells; Inj: sub-cutaneous injection; D: day; ECG: electrocardiogram; ITT: intention-to-treat. *Time frames corresponding to at-hospital visits.

Fig. 2.

Effect of IL-2 treatment on Treg number and frequency. Panels a to d: change in frequency (a-b) and absolute number (c-d) of Tregs throughout the study for all three arms (open triangles, placebo; blue squares, 1 MIU of IL2; black circles, 2 MIU of IL2). a & c: data points indicate mean values, and error bars their associated SEMs. b & d: change in the number and frequency of Tregs between baseline and the three days after the final injection of one treatment cycle (D8) or 3 treatment cycles (D64). Data points represent the per-patient change in Treg frequency (b) and number (d). Three group comparisons by the Kruskal-Wallis H test at D8 and D64 (p < 0.0001) for panel b and d. Panels e-f: iAUC of trough levels of Tregs during the study. Data points indicate mean values, and error bars their associated SEMs for Treg number (e) and frequency (f). Verum to placebo comparisons by the Mann-Whitney U test: *** p < 0.001, ** p < 0.01.

Fig. 3.

Effect of IL-2 treatment on Treg phenotype and suppressive function. Panel a to c: CD25 mfi expression on Tregs at baseline (D1) and 3 days after completion of 3 treatment cycles (D64) in all three study groups: (a) 2 MIU, (b) 1 MIU and (c) placebo. Panels d to f: autologous suppressive function of Tregs measured by in vitro co-culture assay at baseline (D1) and 3 days after completion of 3 treatment cycles (D64) in individuals treated with (d) 2 MIU, (e) 1 MIU and (f) placebo. Panel g: Change in suppressive function of Tregs following 3 cycles of treatment relative to baseline levels in all three groups. Bars represent mean values, and error bars their associated SEMs. Panels h-i: Relationship between the relative change in Treg frequency (h) and Treg CD25 mfi (i) measured by mechanistic immunophenotyping cytometry (x-axis) and Treg suppressive function (Y axis) following 3 cycles of treatment (values at D64 vs D1). Open triangles denote individuals receiving placebo, blue squares 1 MIU and black circles 2 MIU of IL2. **** p < 0.0001, *** p < 0.001, ** p < 0.01, ns: p > 0.05 by the Wilcoxon match paired sign rank test (a to f) and by the Mann-Whitney test (g).

Fig. 4.

Effect of IL-2 treatment on plasma chemokine concentrations. Panels a to c: variation in plasma chemokine levels throughout the study for CCL2 (a), CCL17 (b) and CCL18 (c). Concentrations are expressed as a percentage of baseline value for each individual and points indicate mean values, and error bars their associated SEMs. Open triangles denote individuals receiving placebo, blue squares 1 MIU and black circles 2 MIU of IL2. Three dose comparisons at D64 panels a to c, by the Kruskal-Wallis rank test: (a) p < 0.005; (b) p < 0.0001; (c) p < 0.0028.