EMA401  EMA401 is a drug under development for the treatment of peripheral neuropathic pain. Trials were discontinued in 2015, with new trials scheduled to begin March, 2018. It was initially established as a potential drug option for patients suffering pain caused by postherpetic neuralgia. It may also be useful for treating various types of chronic neuropathic pain  EMA401 has shown efficacy in preclinical models of shingles, diabetes, osteoarthritis, HIV and chemotherapy. EMA401 is a competitive antagonist of angiotensin II type 2 receptor (ATR) being developed by the Australian biotechnology company Spinifex Pharmaceuticals. EMA401 target angiotensin II type 2 receptors, which may have importance for painful sensitisation. Angiotensin II is an octapeptide hormone central to the renin-angiotensin system. It regulates blood pressure control, water fluid homeostasis, and neuronal excitability. Receptor agonists and antagonist of angiotensin II receptors that target various parts of the complicated renin-angiotensin system were developed to increase knowledge of the renin-angiotensin system and aid the development of antihypertensive drug candidates. These investigations led to the discovery of two subtypes of membrane bound G protein-coupled angiotensin receptors within the renin-angiotensin system with vastly different functions: angiotensin II type 1 receptors (ATR) and angiotensin II type 2 receptors (ATR). ATR is the receptor subtype that was found to be mainly responsible for blood pressure, water fluid regulation, and other classical known physiological actions of angiotensin II on the renin-angiotensin system. Phase I clinical trial have indicated that doses of EMA401 up to 400 mg are safe in humans. Spinifex Pharmaceuticals reported the results of a phase 2 randomised placebo controlled - clinical trial results in which 183 patients with postherpetic neuralgia received either oral EMA401 or placebo for 28 days. Those assigned to EMA401 reported significantly less pain associated with post-herpetic neuralgia although the improvement was modest (6.9% better than placebo on a ten point pain scale). There was no evidence of any serious side effects caused by EMA401. Spinifex Pharmaceuticals plans to proceed with larger phase II clinical trial to test higher doses for longer periods of time. A nonrandomized Phase 2 study of EMA401 for the treatment of pain in patients with chemotherapy-induced peripheral neuropathy was approved and is currently underway.