While I am not sure of the exact number, there are current and former Monsanto employees that had worked for FDA. There are also current employees that had worked for other U.S. regulatory agencies like USDA and EPA.
In fact, I worked for USDA for over 22 years in both research and regulatory roles. I spent over 12 years at various USDA-ARS labs in West Virginia, Florida and Washington DC working to develop improved plant varieties using biotechnology methods. For the last 10 years of my time in USDA, I worked in Biotechnology Regulatory Services (the program within USDA-APHIS that regulates field testing and makes deregulation decisions about biotechnology-derived plants). That program has responsibility for assessing the environmental safety of biotech products by verifying that they have no plant pest potential.
After I was offered early retirement from USDA, I still wanted to use my education and knowledge to make positive contributions to agriculture and have long recognized Monsanto as a leader in the field. I was fortunate enough to be offered a position with Monsanto and flexible enough in my non-work life to be able to make that move, even at this stage of my career. As a former regulator with USDA, I have strict U.S. government ethics prohibitions on certain aspects of how and when I can interact with my former Agency.
I have never thought that my work at Monsanto presents a conflict. Although I understand the U.S. regulatory process very well, the employees who work at USDA do independent and thorough reviews of every product that is petitioned for deregulation. I am a firm believer in a person being able to work anywhere they want and being able to use their skills and talents in an ethically acceptable way for any employer, regardless of previous employment.