A covalent conjugate of recombinant human interleukin-10 (IL-10) and polyethylene glycol (PEG), with potential anti-fibrotic, anti-inflammatory, immunomodulating and antineoplastic activities. Upon subcutaneous administration, pegylated recombinant human interleukin-10 AM0010 may activate cell-mediated immunity against cancer cells by stimulating the differentiation and expansion of tumor specific cytotoxic CD8+ T cells. This agent may also lower serum cholesterol levels and reduce atherosclerotic plaques by inhibiting the synthesis of pro-inflammatory cytokines, such as Interferon-gamma, IL-2, IL-3, TNF-alpha, and GM-CSF. The PEG moiety inhibits proteolytic breakdown and clearance of AM0010, which prolongs its half-life, extends the duration of its therapeutic effects and allows less frequent dosing.