Of course, putting an application into a cloud data center is not enough. You have to think about application security, data security and compliance such as PCI DSS 2.0 or HIPAA if you are in the life science space.
But – in addition to cloud security, you need to make sure that your Web application is multi-tenant, i.e. that  you can support multiple customers in the same application, otherwise, the entire model is not going to scale very well.

You’ve built a single-tenant web-enabled application, but need to make it compatible with and effective in a cloud environment. What steps do you need to take to convert your application to a full-fledged, multi-tenant, cloud-ready SaaS application?

This article from IBM is a good checklist on How to convert a web application to a multi-tenant SaaS solution