Was the Lambeth Poisoner also Jack the Ripper?

Three years after Jack the Ripper "disappeared" the Lambeth Poisoner was in the East End of London poisoning prostitutes. He was Dr Thomas Neil Cream. At his execution it is claimed that he uttered the words "I am Jack...." at the moment of being hung. Apart from the different modus operandi there is also the question about the dates that he may have been in London.
Is it possible that Cream was in fact Jack?

In the Shadow of Jack the Ripper: The Lambeth Poisoner