RESEARCH PLAN The study is a randomised, double-blind, placebo-controlled trial with three parallel groups, two assigned different doses of active treatment and one assigned placebo. The total study period for participants will be an average of seven weeks comprised of a two-week placebo treatment run-in period prior to randomisation and a five-week follow-up on randomised treatment. An estimated 400 participants will be commenced on run-in with the expectation that 300 (100 in each group) will go on to randomisation.