Method: This is a multicentre, double blind, randomized 52 week parallel trial comparing active TLA treatment with Placebo. For ethical reasons the randomization is 2 to 1 for active and placebo treatment, respectively. A 2 weeks run-in period is inserted between inclusion and randomization, during which the patient shall get familiar with the use of the patient asthma diary and to adhere to the requirements of the study participation. First 12 weeks an unchanged maintenance medication will be kept and week 13-52 medication will be modified to obtain asthma control according to international guidelines (GINA). After inclusion, run-in, randomization and baseline measurements active/placebo treatment with AA will be implemented over 52 weeks.