AstraZeneca sells a bottle of 28 tablets of Forxiga for $US25 ($A35) after federal government subsidies.
Its active chemical compound dapagliflozin is used to treat type-2 diabetes, heart failure and kidney disease.
The drug brought in $US8.5 billion ($A12 billion) in revenue worldwide for the company in the 2025 financial year and is expected to be its number one revenue growth driver in Australia in 2026 and 2027.
The Swedish parent company AstraZeneca AB and its Australian arm are resisting the release of four generic versions of Forxiga by Sydney-based pharmaceutical company Pharmacor.
They have accused Pharmacor of patent infringement in a Federal Court lawsuit filed in December after it registered its dapagliflozin drugs on the Australian Register of Therapeutic Goods.
On Monday, AstraZeneca successfully blocked  its local rival from listing two of those products on the government-run Pharmaceutical Benefits Scheme - a move that was expected to be finalised from April 1, 2026.
That will now have to wait after Justice Kylie Downes granted an injunction restraining Pharmacor from selling the drugs and forcing it to withdraw the listings.
While it was in the interests of the government and community that Forxiga was sold at a cheaper price, the patent granted a monopoly to AstraZeneca which encouraged and rewarded its invention, the judge said.
"It is therefore in the interests of the Commonwealth, and the public generally, that such invention occurs and is encouraged to continue to occur in the future," she wrote.
In the lawsuit, Pharmacor admits infringement but claims AstraZeneca's patent over the drug - which expires in October 22, 2027 - should be revoked because it is invalid.
Justice Downes noted the firm's case against AstraZeneca was arguable but did not seem to offer a defence against infringement.
Instead, she found the infringement case was strong.
If Pharmacor was not restrained from selling its generic diabetes medicine, AstraZeneca's monopoly on the drug would be destroyed, the judge said.
"This is an irreparable harm," she wrote.
The PBS listing would trigger a 25 per cent reduction to Forxiga's approved ex-manufacturer price which would lead to significant financial losses for AstraZeneca, the judge added.
While she acknowledged Pharmacor would lose its first-mover advantage if blocked from the planned PBS listings, she granted the injunction.
The court heard at least 15 other generic firms had already commenced ARTG registration applications for their own dapagliflozin versions.
A trial has been scheduled to begin in August.
32°C