Transfer to biomedical sciences

Is it possible to transfer from applied medical sciences to biomedical sciences at UCL?

In theory, yes. There are quite a few criteria to be met (e.g. there needs to be capacity on the Biomedical Sciences course, you need to have a good attendance record and be demonstrably engaged with your studies, etc.). There are also deadlnes involved.
I suggest you read UCL's Change your Programme or Route page and Section 5: Programme Transfers of their Academic Manual.

Will international students on scholarship also be able to transfer to another course through this same process?

Did you read the web page I posted the link to? The reason I ask is that point 4 specifically explains how the process impacts those on a student visa and explains where to get further assistance.
I have no idea what the impact on your scholarship would be. That would depend on the terms of that specific scholarship.