Nektar Therapeutics pain drug for knee arthritis fails study

(Reuters) – Nektar Therapeutics said its experimental drug to treat chronic pain in patients with arthritis of the knee failed to meet its main goal in a mid-stage clinical trial. The drugmaker’s shares fell nearly 30 percent in extended trading on Thursday. The study failed mainly because patients on placebo did not show the expected increase in pain scores observed in similar studies, Nektar said in a statement. This lack of a placebo rebound was “unusual,” the company said. Half the 213 patients in the study were dosed with Nektar’s NKTR-181 drug, while the other half was given a placebo. …