IRX-2 and thymosin alpha1 (Zadaxin) increase T lymphocytes in T lymphocytopenic mice and humans

Ann N Y Acad Sci. 2007 Sep;1112:245-55. doi: 10.1196/annals.1415.032. Epub 2007 Jun 28.


Mouse studies showed a synergy of thymosin alpha1 (Talpha1) and a natural cytokine mixture (IRX-2) in increasing T lymphocyte number and responses. Clinical studies with IRX-2 showed increases of T lymphocytes in lymphocytopenic cancer patients but relatively little effect on irradiated, lymphocytopenic patients. The present phase 1 and 2 study shows that Talpha1 enhances the effect of IRX-2 in these lymphocytopenic patients. Patients (seven) were treated with subcutaneously injected IRX-2 (200 units IL-2 equivalence), Talpha1 (1.6 mg/day) (four patients), or the combination of IRX-2 and Talpha1 (seven patients) daily for 10 days. Peripheral blood lymphocytes (T, B, NK) and subsets (CD4, CD8) were measured at the start of treatment and on day 11. IRX-2 and Talpha1 had little or no significant effect. The combination markedly increased various lymphocyte populations (>350 cells/microL). Four patients followed for 6 weeks displayed sustained increases involving both naïve and memory T cells. Responses to persistent infections were observed in three of the four patients and no significant toxicity was observed. Talpha1 and IRX-2 synergize to increase safely T cells in lymphocytopenic patients.

MeSH terms

  • Animals
  • CD4-Positive T-Lymphocytes / drug effects
  • CD4-Positive T-Lymphocytes / immunology
  • CD8-Positive T-Lymphocytes / drug effects
  • CD8-Positive T-Lymphocytes / immunology
  • Cytokines / pharmacology*
  • Cytokines / therapeutic use*
  • Humans
  • Lymphopenia / drug therapy*
  • Lymphopenia / immunology
  • Mice
  • T-Lymphocytes / drug effects
  • T-Lymphocytes / immunology*
  • Thymalfasin
  • Thymosin / analogs & derivatives*
  • Thymosin / pharmacology
  • Thymosin / therapeutic use


  • Cytokines
  • IRX 2
  • Thymosin
  • Thymalfasin