(Reuters) -Amgen on Thursday said its first-quarter profit rose 24%, driven by product sales, and said that while it is premature to speculate on the impact of U.S. tariffs, tax policy would be a more effective way to influence U.S. manufacturing.

President Donald Trump's administration has opened a national security investigation into pharmaceuticals in a bid to demonstrate why the U.S. needs tariffs to increase domestic manufacturing.

"We agree with our peers that the most effective answer is not tariffs, but tax policy," Amgen CFO Peter Griffith said on a conference call.

Johnson & Johnson CEO Joaquin Duato last month said tariffs on pharmaceuticals can create supply chain disruptions and favorable tax policies would be a more effective tool to boost U.S. manufacturing capacity of both drugs and medical devices.

Pharmaceutical companies in recent decades moved production capacity outside of the U.S., including to European Union countries like Ireland, in part because of lower income-tax rates for intellectual property.

Amgen recently announced a $900 million expansion of its Ohio biotech manufacturing facility, joining a number of other drugmakers, including Eli Lilly, Merck and J&J, pledging to increase U.S. plant capacity.

For the first quarter, Amgen reported adjusted earnings per share of $4.90, beating the average analyst estimate of $4.30, as compiled by LSEG. Revenue rose 9% to $8.1 billion, which was in line with Wall Street estimates.

Shares of the biotechnology company, which fell more than 2% in regular trading, were up about 1% at $286 after hours.

For the full year, Amgen said it still expects adjusted earnings per share of $20.00 to $21.20 on revenue of $34.3 billion to $35.7 billion. Analysts, on average, have estimated earnings of $20.63 per share on revenue of $35.1 billion.

Amgen said its 2025 outlook includes the impact of implemented tariffs, but does not account for any future levies, including potential sector-specific tariffs.

The company is slated to present at a medical meeting next month full results from a mid-stage trial of its experimental weight-loss drug MariTide, viewed by many investors as a potential blockbuster.

Amgen is conducting late-stage trials of the drug in patients with and without diabetes, and results from a Phase 2 diabetes trial will be announced later this year.

The company also said the U.S. Food and Drug Administration has lifted its clinical hold on an early-stage trial of a different experimental weight-loss drug known as AMG 513.

The first-quarter results "suggest momentum for established products, but uncertainty is apparent in the newer growth portfolio, both of which highlight the importance of obesity as a future driver for shares," Citi Research analyst Geoff Meacham said in a note to clients.

Amgen's sales of bone drug Prolia rose 10% to $1.1 billion, but the company said it expects lower sales of the medication later in the year as biosimilar competitors are launched.

Sales of cholesterol-lowering medication Repatha rose 27% to $656 million, while sales of arthritis drug Enbrel fell 10% to $567 million.

In the rare disease space, sales of thyroid eye disease drug Tepezza fell 10% to $381 million, and sales of gout treatment Krystexxa were flat at $236 million. Both were acquired with Amgen's 2023 purchase of Horizon Therapeutics.

Sales of rare disease drug Uplinza rose 14% to $91 million. Amgen said the FDA has accepted its application seeking approval of Uplinza as a treatment for myasthenia gravis, with a decision due by December 14.