It's feared life-saving medicines will become unaffordable and out of reach for Australians if the federal government gives the world's largest regional trade agreement the tick of approval.
Health experts are warning measures in the Trans-Pacific Partnership deal concerning intellectual property protections for biologic medicines are "worryingly ambiguous and unclear", with the potential to drive up the cost of expensive medicines and deny many Australians access to them.
Australia currently has a five-year data protection rule which protects the makers of biological drugs by blocking other manufacturers from relying on their research to produce a copy of the product, known as a biosimilar.
The US sought to extend that period to eight years and the Australian government insists the existing five-year protection stands.
But Dr Deborah Gleeson, public health lecturer at La Trobe University, says the text of the TPP appears to give the US scope to apply pressure on Australia to use administrative delays to keep cheaper products off the market for the full eight years.
"It's vague enough that Australia is saying `we don't need to extend the arrangements that we have' but it also allows the US to go back to the pharmaceutical lobby there and say, `We effectively got eight years'," she told AAP on Friday.
Biologic medicines, made using live organisms, tend to be very expensive and represent some of the most cutting-edge medicines and vaccines, such as the melanoma drug Keytruda, which cost $150,000 per person per year before the federal government put it on the Pharmaceutical Benefits Scheme this year.
Public Health Association Australia chief executive Michael Moore says extending the protection rule will make these life-saving medicines more expensive for patients and in some cases, put them out of reach.
And higher prices mean the government won't be able to afford to put as many new drugs on the PBS, he says.
Drug companies want stronger intellectual property protections, arguing five years isn't enough.
They say an eight-year data protection period would have no impact on consumers and would only cost the federal government around $40 million a year.
They argue that's a small price to pay for a move that could stimulate incentive for innovation in Australia.
Trade Minister Andrew Robb says the issue of biologics was discussed over 40 hours and 10 different meetings during the last round of negotiations.
"We did protect the five-year data protection issue," he told ABC radio on Friday.
"We haven't moved one iota on any of that health area."