Sometimes, paying nearly a billion dollars is actually good news. That's the curious math behind Moderna Inc. (MRNA)'s after-hours rally on Tuesday, when shares jumped more than 10% after the company announced it had settled a long-running patent dispute.

The biotech giant said it reached a settlement agreement with Arbutus Biopharma and Genevant Sciences, finally putting to bed all the global litigation related to its COVID-19 vaccine Spikevax and its RSV vaccine mRESVIA. Think of it as a very expensive peace treaty that clears the legal fog from Moderna's horizon.

"Resolving this legacy matter from our pandemic response removes uncertainty and allows us to turn our full focus to Moderna's exciting near-term future," said CEO Stéphane Bancel. In corporate-speak, that translates to: "We can stop worrying about lawyers and start worrying about science again."

Here's how the financials of the settlement shake out. Moderna will write a check for $950 million in the third quarter of 2026. That's not pocket change, but it's a known quantity. The company will then appeal to the Federal Circuit, arguing that its government-contractor immunity from the pandemic era should limit its liability.

If Moderna wins that appeal, the story ends there—no more payments. If it loses, the company has agreed to pay an additional amount, up to $1.3 billion, within 90 days of the decision. So the total potential bill ranges from $950 million to $2.25 billion, but investors clearly think the certainty is worth the price.

The settlement also provides what the company calls "certainty going forward" for its current infectious disease portfolio, which includes pipeline candidates mNEXSPIKE and mCOMBRIAX. In other words, Moderna can now develop these products without looking over its shoulder at patent lawsuits.

Of course, writing a check for up to $2.25 billion does have an impact on the balance sheet. Moderna updated its cash forecast, saying it now expects to end 2026 with $4.5 billion to $5 billion in cash and cash equivalents. That's down from its previous guidance of $5.5 billion to $6 billion—a reduction that essentially matches the initial settlement payment.

The market's reaction was unambiguous. Moderna shares surged 10.23% in after-hours trading, hitting $54.93. When a stock jumps on news that the company might have to pay billions of dollars, you know investors were really worried about the alternative—years of legal battles with uncertain outcomes.

So here's the takeaway: Moderna just bought itself a clear path forward. For a company trying to move beyond its pandemic-era success and build a sustainable pipeline, that clarity might be worth every penny of that $950 million check.