Thymalfasin, a synthetic version of thymosin-α-1, a polypeptide (protein fragment) was being developed by SciClone Pharmaceuticals for the treatment of liver disease. SciClone developed and launched Thymalfasin, under the trade name Zadaxin, for the treatment of hepatitis B and hepatitis C virus infections. The drug is also being developed for the treatment of non-small cell lung cancer (NSCLC), hepatocellular carcinoma, AIDS and malignant melanoma. Thymalfasin exerts a dual action against infections: immune modulating and direct-acting effect. Thymalfasin exerts its immune-modulating activity through the interaction with Toll-like receptors (TLR), a group of proteins involved in the regulation of innate immunity, and in particular with TLR9 and TLR2 on dendritic cells (DCs) and precursor T-cells. Thymalfasin is also able to prevent a pro-inflammatory cytokine storm and possibly autoimmune events. Regarding direct-acting effects, Thymalfasin has been shown to increase the expression of MHC Class I and II, which are important for the antigen presentation and recognition by the immune system of the virally infected cells. v has also been shown to directly inhibit the in vitro growth of virally infected and cancer cells. Thymalfasin is not approved by the FDA but it is widely used in China and some other countries.