What caused Regeneron's tax expenses to fluctuate?

Regeneron's tax expenses fluctuated due to a combination of factors related to their business operations and market conditions:

1. **Income Taxes**: Regeneron's income tax expense for the most recent quarter was $40.4 million. This figure reflects the company's tax liability on its income, which can fluctuate based on factors such as revenue growth, profitability, and tax planning strategies.
2. **Market Conditions and Business Operations**: The fluctuation in tax expenses can also be attributed to changes in market conditions and the company's business operations. For instance, the introduction of new products, expansion into new markets, or changes in regulatory environments can all impact tax expenses.
3. **Tax Planning Strategies**: Companies like Regeneron may also actively manage their tax expenses through tax planning strategies. These can include optimizing their global tax structure, utilizing tax incentives, or managing their tax liabilities across different jurisdictions.

In conclusion, Regeneron's tax expenses are influenced by a mix of income taxes, market conditions, business operations, and tax planning strategies. These factors can cause tax expenses to fluctuate from one period to another.