When people with asthma get respiratory virus such as a cold or flu it often increases asthma symptoms. The investigators will test the study medication to find out if it can prevent the virus spreading from the nose to the lungs.

SNG001 contains Interferon-beta that occurs naturally in the body. In this study, SNG001 will be given by a nebuliser.

The study will consist of a Pre-Treatment Phase into which subjects potentially eligible for the Treatment Phase will be recruited. Subjects will remain in the Pre-Treatment Phase until they experience respiratory virus symptoms at which time they will be further screened for eligibility for entry into the Treatment Phase. If eligible, subjects will be randomised 1:1 to receive SNG001 or placebo once daily for 14 days. Doses will be delivered by a CE marked breath actuated nebuliser (I-neb Philips Respironics). Subjects will be assessed for changes in changes in respiratory virus symptoms and asthma symptoms at home using a text message system, and via telephone questionnaire. Lung function will be measured both at home by the subjects (PEFR only) and in the clinic. Efficacy and safety will be monitored until at least 30 days post treatment.

1. Male or female aged 18 to 65 years of age at the time of screening.

2. Symptoms of asthma for at least 2 years pri or to the Screening Visit, confirmed by a medical history and:

   1. ≥12% and 200mL bronchodilator reversibility at screening or documented in the past, OR,
   2. evidence of bronchial hyper-responsiveness at screening or documented in the past, OR,
   3. a documented hospital admission (including an Accident and Emergency admission) for asthma since the age of 18, OR.
   4. documented evidence that they have attended their GP surgery, out-of-hours clinic (or alternative health care provider) for worsening of asthma symptoms, since the age of 18

3. Must answer "Yes" to the question "Does a cold make your asthma worse?"

4. To have had at least one asthma exacerbation suspected to have been caused by a respiratory virus in the last 24 months which required the use of oral steroids and/or additional treatment with antibiotics on one or more occasion.

5. Must be taking regular inhaled corticosteroids.

6. Pre-bronchodilator FEV1 ≥ 40 % predicted at screening.

7. Post-bronchodilator FEV1 ≥ 50 % predicted at screening.

8. Provide written informed consent.

9. Females of childbearing potential must be using a medically acceptable adequate form of birth control and agree to maintain this usage throughout the duration of and four weeks post the Treatment Phase of the study.

10. Motivation (in the Investigator"s opinion) to complete all study visits, the ability to communicate well with the Investigator and be capable of understanding the nature of the research and its treatment including its risks and benefits.