6.2 Clinical Trials in MS
In 2011, Stein and coworkers [
55] performed a 6-month double-blind RCT of high-dose vitamin D
2 6000 IU, versus 1000 IU of vitamin D
2, with the aim of achieving serum 25(OH)D 130–175 nmol/L in 23 RRMS patients, of whom 19 were treated with IFN-β or glatiramer acetate [
55]. Patients on immunomodulatory treatment had to have at least one relapse within the last 24 months. Brain MRI was performed at baseline and at months 4, 5, and 6, and primary endpoints were the cumulative number of new gadolinium-enhancing lesions and change in the volume of T2 lesions. Median 25(OH)D increased from 54 to 69 nmol/L (Δ 15 nmol/L) in the low-dose and from 59 to 120 nmol/L (Δ 61 nmol/L) in the high-dose vitamin D
2 group. The primary outcome was negative, but after adjusting for entry EDSS, the exit EDSS was higher in the high-dose vitamin D group (
p = 0.05), where four relapses were recorded versus two in the low-dose group (
p = 0.04).
Kampman et al. [
56] compared weekly supplementation with 20,000 IU of vitamin D
3 and placebo for 96 weeks in 68 RRMS patients with EDSS ≤ 4.5 [
56]. Approximately 50% of the patients received immunomodulatory drugs, mostly IFN-β. The trial was designed to study the effect on bone mass density, and no MRI outcomes were included. Neither bone mass density nor turnover were affected by vitamin D supplementation [
57,
58]. The mean annualized relapse rate (ARR) at baseline was low (0.11 and 0.15 in the vitamin D and placebo groups, respectively). Mean 25(OH)D levels increased from 55.6 to 123.1 nmol/L (Δ 67.5 nmol/L) in the vitamin D group and from 57.3 to 61.8 nmol/L (Δ 4.5 nmol/L) in the placebo group. After 96 weeks, there was no significant difference in ARR (absolute difference 0.10, 95% confidence interval [CI] − 0.07 to 0.27), EDSS (absolute difference − 0.01, 95% CI − 0.35 to 0.35), or MS functional composite components, grip strength, or fatigue. Secondary studies revealed no effect of vitamin D on inflammation markers or neurofilament light chain in serum, except a non-significant reduction in neurofilament light chain levels among patients not using conventional disease-modifying treatment [
59,
60]. Serum anti-EBNA1 antibody levels decreased significantly after 48 weeks’ supplementation, but not after 96 weeks [
61].
Soilu-Hänninen et al. [
62] compared weekly supplementation with 20,000 IU vitamin D
3 with placebo for 1 year. All 66 patients had RRMS and had used IFN-β for at least 1 month prior to inclusion. As for the Kampman et al. [
56] study, recent disease activity was not an inclusion criterion, but the ARR was higher (around 0.5 in both treatment arms). The primary endpoint was T2 burden. Mean serum 25(OH)D changed from 54 nmol/L at baseline to 110 nmol/L at 12 months in the vitamin D-treated group (Δ 56 nmol/L), and from 56 to 50 nmol/L in the placebo group. T2 lesion volume increased more in the placebo group (median change 287 mm
3) than in the vitamin D group (median change 83 mm
3). The vitamin D group also accumulated fewer new T2 lesions, but neither of these differences were statistically significant (
p = 0.105 and 0.286, respectively). The ARR at study end was similar (0.26 and 0.28). The vitamin D group did, however, have significantly fewer T1 enhancing lesions (
p = 0.004), as well as a tendency to reduced disability accumulation (
p = 0.071) and improved timed tandem walk (
p = 0.076). An array of soluble inflammatory mediators was analyzed, of which only the latency activated peptide of transforming growth factor (TGF)-β (47–55 pg/mL;
p = 0.0249) was reported as a single regulated molecule within the vitamin D arm [
63].
Shaygannejad et al. [
64] compared calcitriol in escalating doses up to 0.5 µg/day and placebo in 50 RRMS patients. Recent disease activity was not an inclusion criterion. The patients had to be clinically stable during the last month before study entry, and to have 25(OH)D > 100 nmol/L at baseline. Further information about 25(OH)D levels throughout the study was not reported. ARR decreased significantly in both groups, and was 1.04 at baseline and 0.32 at study end in the vitamin D group and 1.04 and 0.40 in the placebo group. EDSS remained stable (1.6) in the vitamin D group and increased from 1.70 to 1.94 in the placebo group. When comparing between groups, only the difference in EDSS change was significant (
p < 0.05).
In 2013, Golan et al. [
65] performed a 1-year double-blind RCT of daily supplementation with 4370 versus 800 IU of vitamin D
3 in 45 patients on IFN-β, with reduction in flu-like symptoms as the primary endpoint. Mean serum 25(OH)D increased from 48 to 68 nmol/L (Δ 20 nmol/L) and from 48.2 to 122.6 nmol/L (Δ 74.4 nmol/L) in the low- and high-dose groups, respectively. The primary endpoint was negative, and there was no difference in ARR at the end of the study (mean ± standard deviation 0.34 ± 0.27 vs. 0.51 ± 0.34 in the low- and high-dose groups, respectively). One patient in the high-dose group with ARR 0 at baseline had three relapses during the study. Circulating interleukin (IL)-17 increased in the placebo (
p = 0.037) but not the vitamin D
3 group.
Achiron et al. [
66] compared the effect of 1 µg/day of the vitamin D
3 metabolite alfacalcidol for 6 months in 158 MS patients with significant fatigue [
66]. The majority of the patients had RRMS, with mean ± standard deviation disease duration 6.2 ± 5.5 years and EDSS score 2.9 ± 2.6. The effect on 25(OH)D levels was not reported. Alfacalcidol decreased the mean relative fatigue severity impact score, which was the primary endpoint, as compared with placebo (− 41.6% vs. − 27.4%;
p = 0.007). There was also an effect on relapses, with eight relapses in the alfacalcidol-treated arm compared with 25 in the placebo arm (
p = 0.006), but not on EDSS.
Sotirchos et al. [
67] compared 10,400 and 800 IU of vitamin D
3 daily for 6 months in 40 RRMS patients. Changes in the proportion of IFN-γ
+ and IL-17
+CD4
+ T cells were the primary endpoints [
67]. The majority of the patients were treated with either IFN-β, glatiramer acetate, natalizumab, or fingolimod. Mean 25(OH)D levels at baseline were 67.6 and 69.3 nmol/L in the low- and high-dose groups, and increased by 17.0 and 86.2 nmol/L, respectively. There was a reduction in the proportion of IL-17
+CD4
+ T cells, CD161
+CD4
+ T cells, and effector memory CD4
+ T cells in the high-dose vitamin D group only. Relapses were the only clinical outcome reported, with one in each study arm.
SOLAR was a randomized, double-blind, multicenter study comparing vitamin D
3 (6670 IU increasing to 14,000 IU per day after 4 weeks) with placebo for 48 weeks, including 232 RRMS patients aged 18–55 years from Denmark, Estonia, Finland, Germany, Italy, Latvia, Lithuania, The Netherlands, Norway, Portugal, and Switzerland [
9]. Three patients did not receive study medication, leaving 229 patients for the intention-to-treat (ITT) analyses. Inclusion criteria were first clinical event occurring within 5 years, EDSS score ≤ 4.0, relapse or gadolinium-enhancing MRI lesion within the last 18 months, no or low vitamin D supplementation, and treatment with IFN-β-1a 44 µg three times weekly for 3–18 months. Median 25(OH)D levels at baseline and week 48 were 53 and 215 nmol/L (Δ 162 nmol/L) in the vitamin D group, and 54 and 49 nmol/L (Δ − 5 nmol/L) in the placebo group. Due to slow inclusion, the primary endpoint was changed during the study from new T2 lesions at week 48 and the proportion of relapse-free patients at week 96 [
68] to no evidence of disease activity (NEDA-3), defined as no relapses, EDSS progression, or combined unique MRI activity (CUA; new gadolinium-enhancing or new/enlarging T2 lesions) at week 48. Overall, 36.3% of patients in the vitamin D group and 35.3% in the placebo group had NEDA-3 at 48 weeks (
p = 0.80). For the secondary endpoints, vitamin D supplementation was associated with a 32% reduction in the number of CUA lesions compared with placebo (
p = 0.0045) and change from baseline in total volume of T2 lesions at week 48 (3.57% vs. 6.07%;
p = 0.035). The vitamin D group also tended to have a lower ARR (30%;
p = 0.17) and risk of EDSS progression (odds ratio [OR] 0.77;
p = 0.39). The proportion of relapse-free patients at week 48 was similar and there were no statistically significant differences between vitamin D
3 and placebo for time to confirmed EDSS progression at week 48. No safety issues appeared.
A subgroup of 53 Dutch participants in SOLAR was analyzed in a substudy, SOLARIUM (SOLAR ImmUne Modulating effects). In the treatment arm of this subgroup, 25(OH)D levels increased from 60 to 231 nmol/L (Δ 171 nmol/L) and remained stable in the placebo group (54 and 60 nmol/L, respectively [Δ 6 nmol/L]). On the whole, there were no differences between treatment arms regarding proportions of regulatory T and B cell subsets or T cell cytokine profiles [
69,
70]. A within-treatment arm 48-week reduction of IL-4-positive T cells (mean 3.7–2.9%;
p = 0.04), a reduction of CD25 protein expression by regulatory T cells, and a reduction in soluble CD25 was observed in the placebo group but not in the vitamin D-supplemented group [
69,
71]. Definitive interpretation of these data requires further study. In the vitamin D group, there was a reduction of anti-EBNA1 IgG levels (median 526–455;
p < 0.001), which was not seen in the placebo-group [
72].
CHOLINE was a multicenter, double-blind, placebo-controlled, parallel-group randomized controlled trial in RRMS patients across 27 centers in France comparing vitamin D
3 (100,000 IU every other week) to placebo for 96 weeks [
10]. A total of 181 patients were recruited, of whom 129 were randomly assigned to receive vitamin D
3 (
n = 63) or placebo (
n = 66). Inclusion criteria were age 18–65 years, EDSS score from 0 to 5, at least one documented relapse during the previous 2 years, stable disease (no episode in the 30 days before screening), serum 25(OH)D concentration < 75 nmol/L, and treatment with subcutaneous IFN-β-1a 44 µg three times weekly for 4 ± 2 months. The primary endpoint was ARR at 96 weeks. Change in time of MRI parameters, EDSS, 3-level version of EQ-5D (EQ-5D-3L), Paced Auditory Serial Addition Task 3, second version (PASAT-3) scores, and safety were the secondary endpoints. Mean serum 25(OH)D levels in the vitamin D
3 group raised from 49.19 nmol/L at baseline to 156.92 nmol/L at 2 years (Δ 107.73 nmol/L). ARR was reduced by the vitamin D
3 treatment but the difference was statistically non-significant in the ITT sample (rate ratio [rR] = 0.799, 95% CI 0.481–1.32;
p = 0.379), as well as on a per protocol basis (rR = 0.630, 95% CI 0.353–1.101;
p = 0.111). Safety was good. A total of 39 patients could not reach the 2-year follow-up; thus, the completers’ population was composed of 90 subjects (45 vitamin D
3 and 45 placebo). In those patients, treatment with vitamin D
3 was associated with a lower ARR (rR = 0.403, 95% CI 0.208–0.814;
p = 0.012), a reduction in the number of new T1-weighted lesions (rR = 0.494, 95% CI 0.267–0.913;
p = 0.025), a lower volume of hypointense T1-weighted MRI lesions (− 312, 95% CI − 596 to − 29;
p = 0.031), and a lower progression of EDSS (− 0.06 ± 0.78 vs. 0.32 ± 0.87, 95% CI − 0.614 to − 0.043;
p = 0.026).