Thalidomide was famously never approved by the FDA, and is used as the main evidence for why the FDA requires entirely separate trials before any product is allowed to be sold in the US. When I worked at a pharma company, we were required to have trial results dating back almost a decade before we were allowed in the US, and even then we were apparently not entirely in the clear. However it did lead to the wildest party in company history when we got our clearance for sale in both the US and CHina within a couple of weeks of each other.