Battle over prostate drug patent reaches Constitutional Court

A Japanese pharmaceutical giant, Astellas, and the University of California, are taking their dispute over a prostate cancer drug patent to the Constitutional Court. They are trying to block local pharma group Eurolab and Dis-Chem from manufacturing and distributing Enzutix, a generic version of Xtandi. The University of California's scientists developed Xtandi, and Astellas is its commercial partner.

Eurolab obtained approval from the South African Health Products Regulatory Authority for Enzutix in January 2023. The University of California and Astellas tried to get an undertaking from Eurolab not to proceed with the generic drug for the life of the patent. However, Eurolab rejected the request, arguing that the University of California was not entitled to apply for a patent for Xtandi in South Africa.

The Commission of Patents agreed with Eurolab, but the Supreme Court of Appeal ruled in favour of the University of California and Astellas in March. The court, however, declined their application to interdict the sale of Enzutix pending the conclusion of the patent litigation. The court noted that Enzutix is a cheaper option than Xtandi, which is financially out of reach for the average South African.

Xtandi costs nearly R361,000 for a year's supply, while Enzutix costs R299,407, a difference of about R60,000. The University of California and Astellas argue that about $1.5bn was spent developing Xtandi, and Eurolab should not be allowed to profit from their invention. They claim that allowing Eurolab to sell Enzutix would undermine the incentive for research and development of new medicines.

The University of California and Astellas also warn that if Eurolab emerges victorious, offshore inventors might shy away from South Africa. They point out that most patents filed in South Africa originate from foreign corporations, with 80% of 11,173 patents filed in 2025 being from foreign corporations.

Eurolab plans to ask the Constitutional Court to rule that it did not infringe a Xtandi patent. The company cites the financial blow that a successful damages action by the University of California would deal it. Eurolab faces potential substantial monetary liability based on a patent that the Commissioner of Patents and the minority found to have been improperly obtained.

Prostate cancer is a significant health concern in South Africa, with prominent South Africans like Nelson Mandela and Desmond Tutu having had the disease. It affects one in 4 black Africans and one in eight whites in South Africa, accounting for 13% of male deaths in the country. The total cost of treating 11,000 new cases in 2022 was estimated at R2.1bn.

Key points

• The Constitutional Court will hear the application from Astellas and the University of California this month.
• Xtandi was developed at the University of California with grant support from the National Institutes of Health and the US Army.
• Eurolab argues that the patent for Xtandi was improperly obtained and that it did not infringe the patent.