A derivative of the antitumor antibiotic spergualin with immunosuppressant activity. Gusperimus inhibits the interleukin-2-stimulated maturation of T cells to the S and G2/M phases and the polarization of the T cells into IFN-gamma-secreting Th1 effector T cells, resulting in the inhibition of growth of activated naive CD4 T cells; this agent may suppress growth of certain T-cell leukemia cell lines.