BRIDGEWATER, N.J.--(BUSINESS WIRE)--Enzon Pharmaceuticals, Inc. (Nasdaq: ENZN) today announced that the U.S. Food and Drug Administration (FDA) has approved its Investigational New Drug (IND) application for PEG-SN38, Enzon’s PEGylated form of SN38, the active metabolite of the cancer drug Camptosar® (irinotecan HCl injection). The Company plans to begin a Phase I trial investigating PEG-SN38 in patients with solid tumors or lymphoma in the fist half of this year.