Alexander: It’s true. First, it has to be tested on animals or in a lab, and then it has to go through clinical trials. Only then is it put through a rigorous review by the FDA, which alone can take years.
Florence: You’re right. I had no idea.
Alexander: In the meantime, I’m suffering needlessly.
Is this a typo? **only then is it put ......
I listened to the conversation on this page and it was read like the text. Which one is correct? "Only then is it put through..." VS " Only then it is put through ...." and what the diffrence is?