BETHESDA, Md.--(BUSINESS WIRE)--REGENERX BIOPHARMACEUTICALS, INC. (AMEX:RGN) (www.regenerx.com) announced today that it has enrolled the first subject in its Phase IB clinical trial in which RGN-352 is being tested in 40 healthy subjects. RGN-352 is an injectable formulation of Tß4 being developed to reduce cardiac damage in patients after an acute myocardial infarction (AMI or heart attack), as well as for other potential systemic uses. The double-blind, placebo-controlled dose-escalating trial includes four groups of ten subjects each to assess the safety of multiple doses at escalating concentrations of RGN-352 injected into the blood stream. Each person will have a 28-day post-treatment assessment with a 6-month follow-up.