Three serious adverse events have led the U.S. FDA to place a clinical hold on Diamedica Therapeutics Inc.’s phase II/III study of DM-199, a synthetic form of human tissue kallikrein-1 for treating acute ischemic stroke. The blood pressure in three participants dropped to a significantly low level shortly after receiving an I.V. dose of the therapy. All three bounced back to normal within minutes of stopping the I.V.