If you see the following error when you try to install a new assembly into the GAC as part of deploying to BizTalk…
Failed to install assembly into the global assembly cache. Result Code: -2146234300
The fix it probably to ensure that you have signed your assembly.
Add your .snk file to the project, right click the project and view its properties, select signing, and ensure you are singing using your key.
Rebuild and redeploy.