Illumina Inc. cut its full-year adjusted profit guidance for the second time in three months as it grapples with the impact of tariffs and China banning imports of its gene-sequencing machines.

The maker of DNA sequencing machines now expects adjusted earnings of $4.20 per share to $4.30 per share for the fiscal year, it said in a statement. That’s a reduction from its March forecast of $4.50 a share, which was down from the $4.50 per share to $4.65 a share it offered in February.

Illumina’s shares declined 2.7% in after-hours trading. They have fallen 40% so far this year, through Thursday’s close.

The lower profit guidance is due largely to the impact of tariffs, the San Diego-based company said Thursday. President Donald Trump’s administration has imposed across-the-board tariffs on most imports, and targeted some countries and industries for additional levies.

Illumina projects revenue this year will decline between 1% and 3%, a cut from its previous forecast of low-single-digit sales growth. The company’s sales have declined for the past two years.

The lower financial forecast and geopolitical turmoil overshadowed what had been a positive start to the year, with first-quarter sales and adjusted profit topping Wall Street’s expectations.

While it dominates the market for machines that decode DNA, Illumina faces multiple challenges to its business.

In March, China banned the import of its gene-sequencing machines as part of a wave of retaliatory measures against fresh US tariffs on all Chinese goods. About a week later, Illumina announced plans to cut about $100 million in costs, partly through changes to stock-based compensation, to account for the impact on its China business.

The company has said it “respects” China’s decision and would continue to serve existing customers in the country.

It’s also facing other challenges. Biotechnology companies that use Illumina’s equipment are holding off purchases and conserving cash in a difficult fundraising environment. The Trump administration’s cuts to the National Institutes of Health, one of Illumina’s largest customers, is also curtailing demand.