Researchers suspect Exelixis used a minor tweak to cabozantinib to sidestep patent cliff

Exelixis' 2025 financial results highlighted the importance of its drug cabozantinib, which has been a major revenue source for the company.

A group of analysts argue that the company introduced a small modification to the molecule, which they describe as trivial, in order to obtain new patent protection and extend market exclusivity beyond the original expiry.

The strategy, if confirmed, would allow Exelixis to maintain sales from the drug while competitors are blocked, effectively hopping over the upcoming patent cliff.

The commentary raises questions about the balance between legitimate innovation and tactics that stretch patent life, and it may attract scrutiny from regulators and investors.