The show from Dutch playwright Maria Goos opened Tuesday to a lukewarm critical reception although Spacey said he "could not have hoped for a better launch," BBC reported Wednesday.
"I think it is going to be a play people recognize themselves in no matter what country they come from because it is about friendship. We all have friends," Spacey said.
Critics were less enthusiastic about "Cloaca," the Latin word for "sewer," a play centered on four male friends in middle age.
"I've had more fun lying in gutters than sitting through this comedy," said Charles Spencer, Britain's Daily Telegraph critic, adding the play was "slick, superficial and as unappealing as its title."
Paul Taylor, critic for Britain's Independent, described "Cloaca" as a "curiously underwhelming affair."