Key Takeaways NVNO stock sank 76.1% after the FDA issued a not-approvable letter for VenoValve.The FDA flagged insufficient NVNO's SAVVE study data and raised surgical safety concerns.NVNO eyes an IDE filing for its non-surgical enVVe valve as the next pipeline step.Shares of enVVeno Medical (NVNO) have crashed 76.1% since Aug. 19. The significant decline was due to the FDA’s not-approvable letter in response to its Premarket Approval (“PMA”) application for Veno Valve.The company submitted the PMA applicat ...