Novo Nordisk A/S said a kidney failure study of its diabetes drug Ozempic showed effectiveness surprisingly early, sending shares of the world’s biggest kidney dialysis providers down.

An independent data monitoring committee recommended halting the study, called FLOW, after finding that an interim analysis had already met pre-set criteria for efficacy, Novo said late on Tuesday. The Danish drugmaker will get full results of the study once the process of closing it is complete, expected by the first half of 2024.

Dialysis provider Fresenius Medical Care AG & Co. plunged as much as 20% in Frankfurt, the most on record, erasing €2.3 billion ($2.4 billion) in market value. Novo shares rose 4%. Other kidney-related stocks such as DaVita Inc. and Baxter International Inc. tumbled in late trading in the US.

The impact of Ozempic and a sister drug for obesity, Wegovy, looks likely to stretch into fields far beyond obesity and diabetes. Another large study recently showed that Wegovy cut the risk of heart attacks and strokes. And WalMart Inc. said last week it’s seeing an impact on shopping demand from people taking the drugs.

The FLOW trial, which started in 2019, looked at the progression of kidney impairment in people with type two diabetes and chronic kidney disease, enrolling more than 3,500 people in 28 countries.

(Updates with shares in the third paragraph)