Table 4

Clinical trials with expanded regulatory T cells (Tregs) in autoimmunity

Diseases and clinical trials	Number of patients, source of cells, dose and route of administration	Outcomes	Comments
Ex-vivo expanded Tregs
Diabetes
1. Marek-Trzonkowska et al (2012)121 Phase I non-randomised study	10 children with type 1 diabetes received autologous Tregs intravenously in two dosing cohorts (10×10⁶ and 20×10⁶ cells/kg body weight). A matched control group of 10 children did not receive a placebo. In the extension study,122 two extra patients were recruited for treatment, and 6 out of the total 12 patients received an additional infusion at 6–9 months (either 10×10⁶ or 20×10⁶ cells/kg) making up a total dose of 30×10⁶ cells/kg. Here, patients were followed up for 1 year.	No serious adverse events. Generally, treated children had lower insulin requirements at 6 months compared with matched controls, and recorded significantly higher c-peptide levels. A higher dose of 30×10⁶ cells/kg was also safely tolerated and was associated with better clinical outcomes (more patients in this group achieved remission, at 1 year with highest fasting and stimulated c-peptide levels and lowest HbA1C levels.	First in-human study of Tregs for autoimmunity
2. Bluestone et al (2015)50 Phase I dose-escalation study	14 adults with type 1 diabetes received intravenous autologous polyclonal Tregs in four dosing cohorts (0.056 to 23.5×10⁸ cells).	Safe. Transferred Tregs were long-lived and stable, with up to 25% surviving up to 1 year. Small sample size and heterogeneity of diabetes did not allow for efficacy assessment	Expanded Tregs had up to 4–8-fold higher suppressive activity than non-expanded Tregs from the same individual
Crohn’s disease
3. Desreumaux et al (2012)123 Phase I/IIa multicentre study	20 patients with refractory Crohn’s disease received intravenously ovalbumin-specific Tr1 cells at 4 dose cohorts (10⁶, 10⁷, 10⁸, 10⁹ cells)	Safely tolerated with few adverse events. Clinical improvement with a reduction in Crohn’s disease activity index and inflammatory bowel disease questionnaires	First in human study of use of Tr1 cells for treatment of autoimmunity. Authors argue that ovalbumin is widely distributed in the GI tract and will activate Tr1 cells.
In-vivo expanded Tregs
HCV-induced vasculitis
4. Saadoun et al (2011)134 Phase I/IIa study in HCV-induced vasculitis	10 patients with HCV-induced vasculitis refractory to HCV therapy received 1.5×10⁶ IU subcutaneous (SC) IL-2 daily for 5 days, followed by three 5 day courses of 3×10⁶ IU/day at weeks 3, 6 and 9.	Safe with no major adverse events. There was a reduction in cryoglobulinaemia in 90% of patients and improvement in vasculitis in 80%. FoxP3⁺ Tregs also increased in peripheral blood.	Treatment did not induce effector T cell activation, vasculitis flare, or increased HCV viremia
Diabetes
5. Long et al (2012)135 Phase 1 study in type 1 diabetes	9 patients with type 1 diabetes received 2–4 mg/day rapamycin for 3 months and 4.5×10⁶ IU IL-2 SC. thrice weekly for 1 month,	Safe with transient Treg increase in the first month but clinical and metabolic data showed worsening of β-cell function in all subjects.	No change in effector T cell frequencies but eosinophils and natural killer cells increased.
6. Hartemann et al (2013)158 Phase I/II randomised, double-blind placebo-controlled study in diabetes	24 patients with type 1 diabetes received either a placebo or one of three doses of IL-2. (0.33×10⁶ IU/day, 1×10⁶ IU/day or 3×10⁶ IU/day) SC for 5 days	Well-tolerated and few treatment related adverse events were reported (flu-like symptoms and injection site reactions). There was a significant dose-dependent increase in the proportion of Tregs in peripheral blood of patients.
7. Todd et al (2016)140 Phase I/II non-randomised, open label, adaptive dose-finding trial	40 adults with type 1 diabetes received one injection of IL-2 SC in different dosing cohorts (0.04×10⁶ to 1.5×10⁶ IU/m²) and followed up for 7 days. The end point was the maximum percentage increase in Tregs (CD3⁺CD4⁺CD25^highCD127^low) from baseline frequency.	Well-tolerated. Optimum dose of IL-2 to induce 10% and 20% increases in Tregs were 0.101×10⁶ IU/m² and 0.497×10⁶ IU/m², respectively.	First adaptive dose-finding trial of IL-2 in diabetes.
8. Seelig et al (2017) 142 Phase I/II response-adaptive trial of repeat doses of IL-2 in diabetes	36 patients with type 1 diabetes received IL-2 at different dose-frequency combinations. Preliminary analysis of all accumulated data after completion of each cohort informed dose-frequencies of the following cohort. An initial learning phase involved 12 participants. Subsequent confirmatory cohorts were eight patients each.	Well tolerated apart from injection site reactions. The optimum regimen to maintain a steady state increase in Treg of 30% and CD25 expression of 25% without Teff expansion was 0.26×10 IU/m² every 3 days.	Preprint data at the time of this review
ALOPECIA AREATA
9. Castela et al (2014)159 Case series of low dose IL-2 in alopecia areata	5 patients received 1.5×10⁶ IU/day IL-2 SC for 5 days followed by 3 courses of 3×10⁶ IU/day at weeks 3, 6, and 9.	Safe with improvement in severity of alopecia tool (SALT) score (evaluated by two independent investigators). Significant increase in the number of Tregs was also seen in 80% of patients.
SLE
10. Humrich et al (2015)137 A case report of low-dose IL-2 in a patient with refractory SLE	1 patient received four treatment cycles of 1.5x10⁶ or 3x10⁶ IU IL-2 SC for five consecutive days with a washout period of 9–16 days after each course.	Clinical improvement was observed with reduction in anti-ds-DNA titre and SLEDAI score,	First evidence of possible therapeutic effect of low dose IL-2 in SLE.
11. von Spee-Mayer et al (2016)136 Phase I study in refractory SLE.	5 patients with refractory SLE were treated daily with 1.5×10⁶ IU IL-2 SC for five consecutive days	Safe with increased CD25 expression in Tregs and increased number of FoxP3⁺CD25^highCD27^low Tregs during the treatment course.
12. He et al (2016)138 Phase I study in active SLE	40 patients were treated with 3 courses of IL-2. Each course consisted of 1×10⁶ IU IL-2 SC alternate days for 2 weeks, with a 2 week drug-free period.	Treatment was safe and associated with a significant increase in CD25^highCD127^low Tregs in the CD4⁺ T cell population. Significant clinical improvement was also observed such that up to 89.5% of patients had at least a 4-point decrease (SRI-4) in the SLEDAI after 12 weeks.

IL, interleukin; SLE, systemic lupus erythematosus; SLEDAI, Systemic Lupus Erythematosus Disease Activity Index; UC, umbilical cord.