This conversion basically represents a standard workflow in Wwise, where you export a project (.wproj) to a finished audio export (.wem). It is highly unlikely that any other program would be capable of this conversion as projects can usually be only exported in the original program.
Convert Wwise project to Wwise Encoded Media audio file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert wproj to wem on Windows
A professional audio management and procesing utility
Convert from wproj file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.