Prilosec to Nexium (2000–2001)
As AstraZeneca's blockbuster acid-reflux drug omeprazole (Prilosec) neared US patent expiry, the company launched esomeprazole (Nexium) in 2001. Nexium was the S-enantiomer, a mirror-image version of the same molecule, marketed as a distinct new drug with its own patent protection.
Nexium became one of the best-selling drugs in the world as Prilosec went generic.
The case became the template for product lifecycle management, where chemical variants extend commercial exclusivity beyond an original patent.
It shows how a chemical modification of an approved drug can reshape market competition, the same logic Handa applied with a different salt form.
