Please start over

Sure, I can provide a fresh analysis.

The stock price of Elanco Animal Health (ELAN) experienced an increase of 2.87% on September 19, 2024, following the FDA approval of Zenrelia, a once-daily oral JAK inhibitor for dogs with allergic and atopic dermatitis. However, on September 20, 2024, the stock price decreased by 6.64%. This mixed reaction can be attributed to several factors:

1. **Market Perception and Analyst Ratings**: Despite the FDA approval, the stock rating remained Neutral with a price target of $16.00, suggesting that the market did not anticipate a significant price surge based on the FDA approval.
2. **Label Warnings and Efficacy Concerns**: The FDA approval of Zenrelia came with a boxed warning regarding the need to discontinue the drug 28 days to 3 months before any vaccination, which could potentially slow down market penetration. Additionally, there were concerns about the actual efficacy of Zenrelia compared to the market incumbent JAK inhibitor, Apoquel, as indicated by a higher placebo effect and a lower rate of clinical remission of itch in the FDA study.
3. **Investor Expectations**: Despite the approval, investor expectations for Zenrelia over the next two years were already elevated, which could imply that the market had already priced in the potential of the drug.
4. **Competitive Market Dynamics**: The canine dermatology market is competitive, and Zenrelia faces competition from established treatments like Apoquel. The market response to Zenrelia may be influenced by its positioning relative to these competitors.
5. **Short-Term Impact**: The stock price movement may also reflect short-term market dynamics, where the initial approval news was already factored into the stock price, and any subsequent price target adjustments or market perceptions might have led to a decrease.

In conclusion, while the FDA approval of Zenrelia was a significant milestone for Elanco, the stock price increase was not substantial due to a combination of factors including market perception, label warnings, efficacy concerns, investor expectations, competitive dynamics, and short-term market impacts.