Medical technology business Smith & Nephew has revealed negative results for the phase-three study on its living cell spray-on therapy, which failed to meet its primary goal.The treatment is designed to work with the body's own cells to stimulate healing of venous leg ulcers, but failed to result in a statistically significant improvement in healing over a placebo.Olivier Bohuon, Chief Executive Officer of Smith & Nephew, said: "A thorough assessment is under way to determine why the preliminary results of the first phase three study are inconsistent with the strongly positive phase 2a/2b results."While this is an unexpected and disappointing development with this one product, we remain excited by the prospects for advanced wound bioactives as unique treatments for unmet patient needs."The FTSE 100 group will carry out full analysis of the data and study methodology and is planning a second phase-three study in the European Union, with the results expected to be released in 2016.In 2011, the phase-two study results demonstrated that the therapy was able to meet both its primary and secondary endpoints and entered a phase three trial in North America in 2012.This study reported complete wound closure over a 12-week period in patients treated with the drug and standard care compression.