The hydrochloride salt form of a metal chelating agent with potential anti-angiogenic activity. Trientine chelates excess copper (Cu) ions in the body; the excess copper is subsequently removed from the body through the kidneys. As Cu is an essential cofactor for cuproenzymes, such as superoxide dismutase 1 (SOD1), depletion of copper may inhibit the activation of signal transduction pathways required for cellular proliferation and angiogenesis. In addition, trientine may inhibit copper-induced secretion of interleukin-8 (IL-8).