The FDA's rejection of Merck's new drug application for gefapixant is a significant regulatory hurdle, potentially delaying the drug's entry to the market and affecting Merck's revenue projections for this treatment. While the CRL does not pertain to safety, the need for additional evidence of effectiveness could lead to further research and trials, incurring more costs and time. This news is likely to be taken negatively by investors in the short term, as it represents a setback in Merck's pipeline development.