Eli Lilly on Friday said it will spend more than $3.5 billion to build a manufacturing plant in Pennsylvania’s Lehigh Valley that will help make its next-generation obesity drugs.

That includes a closely watched experimental drug called retatrutide, which has shown the highest weight loss seen to date for any treatment in a late-stage trial.

It is the fourth facility in a string of new planned U.S. investments by the pharmaceutical giant. Lilly announced in February 2025 that it would spend at least $27 billion to build new domestic manufacturing facilities, adding to $23 billion in previous investments since 2020.

On Thursday, President Donald Trump said Lilly CEO Dave Ricks has told him the drugmaker aims to build six plants in the U.S. But Lilly has not confirmed those plans.

The company on Friday said it expects construction of the Pennsylvania plant to start this year and for the site to be operational in 2031.

That added production capacity for upcoming weight loss treatments is crucial. Retatrutide is viewed as a key pillar of Lilly’s long-term obesity strategy after its popular injection Zepbound and upcoming obesity pill.

Some health experts say retatrutide, which works by targeting three gut hormones rather than one or two, can reach patients with severe obesity who would benefit from even more weight loss than what existing injections can offer. Lilly plans to release data from seven other Phase 3 trials on the drug this year.

The company and its chief rival, Novo Nordiskhave invested heavily in boosting production capacity after previously facing supply shortages for their existing weekly injections in the U.S.

Preparing enough supply of upcoming drugs is also central to Lilly’s efforts to maintain its dominance in the booming GLP-1 market. The company secured the majority share in the space last year for the first time, overtaking Novo.

But the Danish drugmaker is hoping to close the gap with the launch of the first-ever GLP-1 pill for obesity this month, which has already racked up thousands of U.S. prescriptions. Lilly has its own pill, orforglipron, that could win approval and launch later this year.

Drugmakers have been scrambling to boost their production in the U.S. after threats by President Donald Trump to impose tariffs on pharmaceuticals imported into the U.S. But concerns about those potential tariffs have eased following voluntary drug pricing deals with Trump in recent months that exempt companies — including both Lilly and Novo — from the levies for three years.

Eli Lilly said the Pennsylvania site will bring 850 jobs to the area, including engineers, scientists, operations personnel and lab technicians, as well as 2,000 construction jobs.