A phase 1 proof-of-concept study evaluating safety, tolerability, and biological marker responses with combination therapy of CTLA4-Ig and interleukin-2 in amyotrophic lateral sclerosis

Abstract

Objective: To determine whether a combination therapy with abatacept (CTLA4-Ig) and interleukin-2 (IL-2) is safe and suppresses markers of oxidative stress, inflammation, and degeneration in ALS.

Methods: In this open-label study, four participants with ALS received subcutaneous injections of low dose IL-2 (1 × 10⁶ IU/injection/day) for 5 consecutive days every 2 weeks and one subcutaneous injection of CTLA4-Ig (125 mg/mL/injection) every 2 weeks coinciding with the first IL-2 injection of each treatment cycle. Participants received a total of 24 treatment cycles during the first 48 weeks in this 56-week study. They were closely monitored for treatment-emergent adverse events (TEAEs) and disease progression with the ALSFRS-R. Phenotypic changes within T cell populations and serum biological markers of oxidative stress [4-hydroxynonenal (4-HNE) and oxidized-LDL (ox-LDL)], inflammation (IL-18), and structural neuronal degeneration [neurofilament light chain (Nf-L)] were assessed longitudinally.

Results: CTLA4-Ig/IL-2 therapy was safe and well-tolerated in all four participants over the 56-week study. During the first 24 weeks, the average rate of change in the ALSFRS-R was +0.04 points/month. Over the 48-week treatment period, the average rate of change was -0.13 points/month with one participant improving by 0.9 points/month while the other three participants experienced an average decrease of -0.47 points/month, which is slower than the average - 1.1 points/month prior to initiation of therapy. Treg suppressive function and numbers increased during treatment. Responses in the biological markers during the first 16 weeks coincided with minimal clinical progression. Mean levels of 4-HNE decreased by 30%, ox-LDL decreased by 19%, IL-18 decreased by 23%, and Nf-L remained the same, on average, in all four participants. Oxidized-LDL levels decreased in all four participants, 4-HNE and IL-18 levels decreased in three out of four participants, and Nf-L decreased in two out of four participants.

Conclusion: The combination therapy of CTLA4-Ig and IL-2 in ALS is safe and well-tolerated with promising results of clinical efficacy and suppression of biomarkers of oxidative stress, neuroinflammation and neuronal degeneration. In this open-label study, the efficacy as measured by the ALSFRS-R and corresponding biomarkers suggests the therapeutic potential of this treatment and warrants further study in a phase 2 double-blind, placebo-controlled trial.

Clinical trial registration: ClinicalTrials.gov, NCT06307301.

Keywords: CTLA4-Ig; amyotrophic lateral scelerosis; clinical trial; interleukin-2 (IL-2); lipid perodixation; neuroinflammation; oxidative stress; phase 1.

Figure 1

Treg numbers and suppressive function increased with CTLA4-Ig/IL-2 treatment throughout the 48-week treatment period. Changes in Treg suppressive function (A), the percentage of CD4⁺CD25⁺FOXP3⁺ cells (B), the percentage of CD4⁺CD25⁺ cells (C), the percentage of CD4⁺CD25⁻ cells (D), and the percentage of CD8⁺ cells (E) throughout the study are shown. Changes in CD25 protein expression (F) and FOXP3 protein expression (G) in the CD4⁺CD25⁺FOXP3⁺ population by mean fluorescent intensity (MFI) throughout the study are shown. Data were analyzed by a one-way ANOVA with post-hoc Tukey test and p values less than 0.05 were considered significant. Data are expressed as mean ± SD. ^*p < 0.05, ^**p < 0.01.

Figure 2

Disease progression remained relatively unchanged during the first 24 weeks of CTLA4-Ig/IL-2 treatment. Dashed vertical lines represent either a CTLA4-Ig injection alone (week 0) or CTLA4-Ig injection simultaneously with 5 consecutive days of IL-2 injections (week 2–48). Clinical progression is depicted by the ALSFRS-R over the first 24 weeks (A) and over the entire 56-week study (B). At week 24, participant #1 improved by four points, participant #2 improved by three points, participant #3 was unchanged, and participant #4 decreased by six points. Throughout the entire 48-week treatment period, participant #1 improved by 11 points, participant #2 decreased by five points, participant #3 decreased by five points, and participant #4 decreased by seven points.

Figure 3

Biological markers of oxidative stress, inflammation, and structural degeneration showed a decreasing trend during the first 16 weeks of CTLA4-Ig/IL-2 treatment. Dashed vertical lines represent either a CTLA4-Ig injection alone (week 0) or CTLA4-Ig injection simultaneously with 5 consecutive days of IL-2 injections (week 2–24). The horizontal gray solid line and dashed lines indicate healthy control mean ± SD (n = 23) for each marker, respectively. Changes in the levels of two markers of oxidative stress, 4-HNE (A) and ox-LDL (B); a marker of inflammation, IL-18 (C); and a marker of neuronal structural degeneration, Nf-L (D) are shown over the first 24 weeks of the study in all four participants.