Safety, pharmacokinetic, and pharmacodynamic evaluations of PI-2301, a potent immunomodulator, in a first-in-human, single-ascending-dose study in healthy volunteers.

PI-2301 is an amino acid copolymer acting as an immunomodulator for the treatment of autoimmune diseases. The present study evaluated the safety, pharmacokinetics (PK), and pharmacodynamics of PI-2301 in a single ascending dose, first-in-human study involving healthy, male adult volunteers. A total of 56 subjects were given a subcutaneous injection of PI-2301 ranging from 0.035 to 60 mg. The only consistent side effect was transient injection site reactions. We describe, for the first time, a pharmacokinetic assay to monitor amino acid copolymer concentration in human serum. PI-2301 was detected in the serum of subjects in the 10-, 30-, and 60-mg cohorts. Maximum serum concentration was achieved between 10 and 30 minutes postdosing with some compound detected 4 hours after dosing. PI-2301's lasting immunological properties were evident by an ex vivo recall assay showing T-cell proliferation and IL-13 production in subjects dosed with 1, 3, or 10 mg of PI-2301, up to 6 months after dosing. A transient increase in chemokine CXCL9 and CXCL10 plasma levels was seen in subjects dosed with 30 or 60 mg of PI-2301. These results are highly consistent with our preclinical findings and suggest that PI-2301 could facilitate the expansion of a favorable immune posture in patients with autoimmune disorders.