While he was in medical school, he founded a company called Ganogen to develop methods to use fetal tissue implants in organ transplantation.

[3][4] In 2012 Gu and Nick K. Chang, who had also gone to Stanford and was a Duke medical student, founded Ganogen, Inc., as a vehicle to further develop these methods.

[3][5] Gu put the work on hold when he started his residency,[6] and took down the company's website after he was harassed in the wake of the Planned Parenthood 2015 undercover videos controversy.

A May 17 letter to Gu from VUMC General Counsel Michael Regier, which was obtained by the Duke Chronicle, cited "lack of sufficient improvement in performance and conduct in key areas.

[16] Gu was noted for having a vocal presence on the site Twitter, where he advocated for social justice causes,[17] and for his critical commentary of then-U.S. president Donald Trump.