Shortages of weight-loss drugs are driving pharmaceutical companies to scramble to shore up supplies.

Why it matters: Booming demand for anti-obesity drugs, known as GLP-1s, has led to a windfall of revenue for pharma giants like Novo Nordisk and Eli Lilly.

Driving the news: Novo Nordisk parent company Novo Holdings on Monday announced a two-part deal valued at $16.5 billion to buy drug manufacturer Catalent.

• The deal will result in Novo Nordisk acquiring Catalent drug-making sites in Italy, Belgium and the U.S., intended to increase manufacturing capacity for its Wegovy and Ozempic drugs.

Meanwhile, Lilly reported Tuesday that it's pressing ahead with its "manufacturing expansion agenda."

The impact: Lilly, which sells Mounjaro and Zepbound, reported a 39% increase in U.S. fourth-quarter revenue from a year earlier, to $6.46 billion.

• 27 percentage points of that jump was due to price increases, while 12 points were due to volume increases. Mounjaro drove the higher prices, Lilly said.

Yes, but: Drug manufacturing takes years to ramp up — and this is no exception.

• Novo Nordisk said it doesn't expect the Catalent deal to increase its production capacity until 2026.
• And despite its manufacturing expansion, Lilly said it still expects demand for GLP-1 drugs to "outpace supply" this year.

What they're saying: "These are technically complex facilities," Lilly CEO David Ricks said today on an earnings call.

• "There's not an infinite number of people who know how to set them up. And the supply chain for the machines that make the products is also constrained. So at this point, I don't think there's an easy way forward."

The bottom line: Shortages will continue.

• "I know it's frustrating for investors, it's frustrating for us. It's even more frustrating for patients," Ricks said.