Endorsement Letter

Im in the process of applying for a hospital inclusion for a new drug and the therapeutics committee needs an endorsement letter from healthcare professionals within the hospital to endorse the drug..problem is its my first time to do this and the HCP's requested me to make a formal letter for them to just sign..can u help me on any ideas how to start or any best way to create a good letter or any sample letters for this really need ur help big time thanks!