I got my H1B petition approved in May 2016, but I chose consular notification. I have not traveled outside the States to apply for an H1B visa to activate my H1B status, so I am still working under Employer A with my OPT STEM extension (which will expire in July 2017).
If I would like to change to a new job, is it possible for my new employer (say, Employer B) to transfer my H1B before I activate it? Are there any risks that I will lose my H1B if they do the transfer?

Thank you in advance!