A Study of the Safety and Efficacy of A-60444 in Adults With Respiratory Syncytial Virus (RSV) Infection Following HSCT

Objectives Primary Objectives: * Pilot Study: A preliminary assessment of the exposure and safety of oral A-60444 in post-stem cell transplant patients with RSV infection. * Main Study: To determine the antiviral effect of oral A-60444 versus placebo in post-stem cell transplant patients with RSV infection and to assess the safety of oral A-60444 in post-stem cell transplant patients with RSV infection. Secondary Objectives: * To study the pharmacokinetics of A-60444 in the presence of concomitant medications such as immunosuppressants and antifungals, in post-stem cell transplant patients with RSV infection. Sample Size: Six patients will be included in the open, pilot phase of the study and there is an option to include a further 22 patients into the main, placebo-controlled study, depending on the pilot study findings. An independent Data Safety Monitoring Board will assess the findings of the pilot study.