Immunosuppressive properties and circulating life of Achromobacter glutaminase-asparaginase covalently attached to polyethylene glycol in man.

The immunosuppressive effects and circulating life of Achromobacter glutaminase-asparaginase (GA) covalently attached to polyethylene glycol (PEG) were examined in human subjects following a single iv dose of 1000 IU/m2. Plasma half-life of PEG-GA was 72 hours. Skin test reactivity to recall antigens (mumps and tuberculin) was lost in all four patients tested. In vitro phytohemagglutinin-induced blastogenesis, "natural killing," and phytohemagglutinin-induced cell cytotoxicity was diminished as long as enzyme levels were detectable. In vivo and in vitro activities returned to normal following total plasma clearance of enzyme.