Stephen Port was charged with four counts of murder last year but the new allegations relate to eight living complainants.
The 41-year-old from Barking denied the charges during a pre trial hearing at the Old Bailey.
He allegedly met the four murder victims on the internet between June 2014 and September 2015.
It is alleged he then invited them to his flat on Cooke Street where he is said to have poisoned them with the psychoactive drug GHB.
Mr Port faces 29 charges in total and is set to stand trial on 4 October.
He was originally charged with four counts of murder and four of administering a poison, but at the Old Bailey on Monday prosecutors added six more counts of administering a poison, seven charges of rape and four of sexual assault.
Mr Port now also faces four alternative charges of manslaughter.
These are alleged to have occurred between 2011 and 2015.
Some of the charges relate to the deaths of:
The deaths were not initially linked but after further investigation they were referred to the Metropolitan Police homicide and major crime command in October last year.
The force has referred its handling of the case to the Independent Police Complaints Commission (IPCC).
A man accused of murdering four men in east London has also been charged with poisoning, rape and sexual assault.