Markets

Kiniksa Stock Soars 22%, Adding $1.3 Billion, After Raising Its Arcalyst Forecast

The drugmaker's shares hit a 52-week high after third-quarter profit climbed and management lifted its full-year Arcalyst outlook.

Kiniksa Pharmaceuticals International, which sells the pericarditis drug Arcalyst, saw its shares soar 22.23% to $89.20 at Tuesday's close, a new 52-week high, after it raised its full-year Arcalyst sales forecast alongside third-quarter results. The jump added $1.3 billion in market value.

Forecast lifted to $1.05 billion

In an 8-K filed Tuesday, Kiniksa raised its 2026 Arcalyst net product revenue forecast to a range of $1.045 billion to $1.050 billion. The prior range was $980 million to $995 million.

Third-quarter revenue reached $286 million, up 58.1% from a year earlier, the company reported. Profit was $47.3 million, up from $18.4 million a year earlier, according to a MarketWatch report on the results.

It was the stock's biggest one-day gain since July 28, when it rose 25.0%. Kiniksa's total market value stood at $6.96 billion at Tuesday's close.

A pericarditis drug carries the company

Kiniksa, a biopharmaceutical company focused on heart and blood vessel conditions, has one commercial product: Arcalyst, a weekly injection approved in the United States for recurrent pericarditis, a painful inflammation of the sac around the heart. It is also approved for two rare inflammatory conditions, CAPS and DIRA. Kiniksa licenses the drug from Regeneron, which makes it and splits profits with Kiniksa evenly.

The stock entered the session up about 77% this year as of Monday's close, well ahead of the S&P 500's gain of about 12%.

Blockbuster talk and a 2027 readout

Management said on the day of the results that Arcalyst is positioned to reach blockbuster status this year. A late-stage readout for the monthly follow-on drug is due in the second half of 2027, ahead of a possible launch in 2028 to 2029.

The next hard data point is the second half of 2027, when the late-stage readout on Kiniksa's monthly follow-on drug is due.