indication

Indicated as an adjuvant for influenza vaccine in elderly patients and as an adjuvant for both influenza and hepatitis B vaccines in chronic hemodialysis patients who failed to achieve adequate antibody titers from previous immunization.

pharmacology

Thymalfasin is a 28-amino acid polypeptide produced synthetically but originally isolated from thymosin fraction 5, a bovine thymus extract containing a number of immunologically active peptides. In vitro studies have shown that Thymalfasin can influence T-cell production and maturation, stimulate production of Th1 cytokines such as interferon-gamma and interleukin-2, and activate natural killer cell-mediated cytotoxicity.

mechanism of action

The mechanism of action of thymalfasin is not completely understood but is thought to be related to its immunomodulating activities, centered primarily around augmentation of T-cell function. In various in vitro assays, thymosin alpha 1 has been shown to promote T-cell differentiation and maturation; for example, CD4+, CD8+, and CD3+ cells have all been shown to be increased. Thymosin alpha 1 has also been shown to increase production of IFN-g, IL-2, IL-3, and expression of IL-2 receptor following activation by mitogens or antigens, increase NK cell activity, increase production of migratory inhibitory factor (MIF), and increase antibody response to T-cell dependent antigens. Thymosin alpha 1 has also been shown to antagonize dexamethasone-induced apoptosis of thymocytes in vitro. In vivo administration of thymosin alpha 1 to animals immunosuppressed by chemotherapy, tumor burden, or irradiation showed that thymosin alpha 1 protects against cytotoxic damage to bone marrow, tumor progression and opportunistic infections, thereby increasing survival time and number of survivors. Many of the in vitro and in vivo effects of thymosin alpha 1 have been interpreted as influences on either differentiation of pluripotent stem cells to thymocytes or activation of thymocytes into activated T-cells. Thymalfasin also has been shown in vitro to upregulate expression of toll like receptors (TLR) including TLR2 and TLR9 in mouse and human dendritic cells, as well as activate NF-kB and JNK/P38/AP1 pathways. Thymalfasin's activation of dendritic cells provides another possible pathway explaining thymalfasin's immunomodulatory and antiviral effects.

toxicity

There are no reported instances of deliberate or accidental overdosage in humans. Animal toxicology studies have shown no adverse reactions in single doses up to 20 mg/kg and in repeated doses up to 6 mg/kg/day for 13 weeks, which were the highest doses studied. The highest single dose tested in animals represents 800-times the clinical dose.

absorption

Rapidly absorbed with peak serum levels achieved at approximately 2 hours.

half life

Approximately 2 hours. There is no evidence of accumulation following multiple subcutaneous doses.