Circassia, once considered one of the UK's most promising biotech companies, has faced an uncertain future since its much-hyped cat allergy drug failed spectacularl y in final clinical trials nine months ago, sending its shares downy by 64pc. Since then, Steve Harris, the chief executive, has attempted to set out a fresh direction, focusing on Circassia's respiratory portfolio, which includes a pipeline of generic drugs and an asthma monitoring device called Niox that is already on the market. Under the terms of the deal with AstraZeneca, Circassia will get the commercial rights in the US to two of its respiratory drugs, Tudorza and Duaklir.