Positives

• In a phase 2a basket trial, 81 patients with one of 13 different autoimmune diseases received 1 million IU/day for 5 days, then fortnightly injections, and saw selective Treg expansion plus disease-score improvement in lupus, Sjogren's, Behcet's, ankylosing spondylitis, and systemic sclerosis ScienceDirect.
  
  
• Treated patients carried a long-lived anti-inflammatory gene-expression signature in T and NK cells one month after the course, the inverse of the inflammatory signature seen in COVID-19 patients medRxiv.
  
  

Negatives

• In a phase 2b ALS add-on trial, patients on low-dose IL-2 had injection-site reactions and transient flu-like symptoms, with overall safety acceptable but not free of adverse effects Lancet.
  
  
• Patients with ME/CFS or Long COVID seeking the therapy noted that no dedicated Long COVID low-dose IL-2 trial has yet reported, leaving them reliant on extrapolation from autoimmune cohorts PMC.
  
  

Hurdles & Side Effects

• A patient interested in trying Proleukin off-label found access limited to research centers and trial sites, with subcutaneous dosing courses requiring physician supervision PubMed.