The Food and Drug Administration allows faster drug approvals based on preliminary study data if the drug fulfills an unmet medical need. But the speedy approval comes with a promise that the drugmaker does another clinical trial once the drug is on the market to prove it really works. If not, the FDA can rescind the approval. How are the companies doing and how well does the agency enforce that system? Pharmaceuticals correspondent Sydney Lupkin investigated the 30-year track record for accelerated approvals. Today, her findings on stalled trials and missing evidence.