Campaigners are calling on the government to urgently intervene over the cost of a drug that could extend the lives of thousands of children but which manufacturers have set at £105,000 per patient per year, a price the NHS cannot afford.

For more than two years an emotive battle has been raging over Orkambi, which tackles the cause of cystic fibrosis. Previously, children with the genetic disorder did not often survive to adulthood and even today, half will be dead before the age of 32. Orkambi could extend lives, but negotiations over the price the NHS should pay have been in stalemate since July, with the pharma company that makes it refusing to reduce the price.

Countries all over the world are struggling with the high prices of new medicines, which has led to anger and campaigning, particularly over cancer drugs. The NHS has forced down prices by requiring drugs to go through a cost-effectiveness appraisal and capping the price it will pay.

Vertex, based in Boston in the US, has priced the drug at £105,000 per patient per year, which NHS England says is unaffordable. Vertex turned down its offer in July of £500m over five years for access to Orkambi and its other cystic fibrosis drugs, saying it was inadequate and unfair. It has also withdrawn the newer and more effective drug Symkevi from the approval process, which means it will not be available to any NHS patients.

Campaigners have said the company had earned $2.5bn from sales of the drug in 2017, which was discovered thanks to funding from a cystic fibrosis charity and taxpayers’ money from the National Institutes of Health in the US. Vertex paid $3.3bn for the patents. Its chief executive, Dr Jeff Leiden, was paid at least $17.2m in 2017, according to SEC filings reported by Reuters last year.

There is an urgency to the campaigning. Christina Walker, whose eight-year-old son Luis has the disorder, said: “We think the government has got to step in otherwise it could be months and months. It could be another year.

Quick Guide How can medicine be so expensive? Show Are there precedents for the battle over the cost of Orkambi? The fight for access to Orkambi – which manufacturers have set at more than £100,000 per patient per year – has much in common with the fight for the breast cancer drug Herceptin back in 2006. The underlying issues are the same – new, innovative drugs are launched at sky-high prices that pharmaceutical companies claim are necessary to recoup their costs, but healthcare providers and patients say they cannot afford. How can a drug be so expensive? The drugs with the highest price tags are often those for which there are fewer patients, so less profit to be made. Cystic fibrosis is a rare disease, affecting 10,400 people in the UK, where the genetic fault is most common, and about 100,000 worldwide. Drugs that cure a disease may be more expensive than those that have to be taken for many years. How does the NHS try to control the cost of drugs? In 2017, the NHS drugs bill was £16bn and rising at 7% a year. The NHS has actively tried to keep costs down by bringing in an appraisal mechanism, run by the National Institute for Health and Care Excellence (Nice), to ensure only drugs that are value for money are used. This has effectively capped and reduced drug prices. Has that effort been successful in the past? The biggest pharmaceutical companies are multinational and all of them look to world markets, making it more difficult to secure price reductions. But the NHS has been relatively successful in negotiating prices down. Cancer drug Kadcyla arrived in 2015 priced at £90,000 per patient per year. After a lot of noise and negotiation, the manufacturer, Roche, agreed an undisclosed discount for the NHS. Photograph: Fahroni/iStockphoto

“Cystic fibrosis doesn’t wait for all this. My little boy has got an infection he may never eradicate that is multi-resistant to antibiotics. The cumulative effect is what shortens people’s lives.”

The campaigners want the government to set aside Vertex’s patent on Orkambi to allow cheap versions to be made through a legal provision called crown use. Under the 1977 Patents Act, the state can effectively override a patent in the national interest. It has rarely been used, but was invoked in the 1960s to obtain cheap generic versions of the antibiotic tetracycline for NHS hospitals from Italy, against the wishes of the patent holder Pfizer. It has more recently been threatened but not used in disputes over hepatitis C diagnostic tests and machines for treating kidney stones.

Vertex would be compensated under the UK law with a much smaller sum than it could otherwise earn from its monopoly of the three cystic fibrosis drugs. Another combination is also in the pipeline that Vertex hopes could treat 90% of patients.

Bill Wiggin, the Conservative MP for North Herefordshire, will ask the government to invoke crown use for Orkambi in an adjournment debate in the House of Commons on Monday. “Vertex refused the largest ever financial offer the NHS has made in its entire history for this medicine,” said Wiggin.

He added: “Crown use licensing can prevent pharmaceutical companies from taking advantage of incredibly vulnerable people.”

Christine Walker with her son Luis, who has cystic fibrosis, which clogs up the lungs. He uses a nebuliser to help him breathe. Photograph: Martin Godwin/The Guardian

Parents backing the proposal said in a letter to Theresa May and health secretary Matt Hancock that access to the drugs was urgent.

They wrote: “We cannot explain, let alone expect you to understand, the sheer dread and helplessness it causes us to know that we are likely to outlive our children. The anguish in knowing that a drug exists that can change that – sparing them unnecessary suffering and decline in health – but that they are denied access, is unbearable.”

Dr Andrew Hill of the pharmacology department of the University of Liverpool advised the access to medicines group Just Treatment, which is launching the campaign with the parents, on the likely cost of a generic version of Orkambi. “It could be made for a maximum of £5,000 [per patient, per year],” he told the Guardian.

He said drug companies were not respecting the value for money judgments of the National Institute for Health and Care Excellence (Nice), which advised NHS England that the cost was prohibitive. “It is happening with so many cancer drugs and now cystic fibrosis,” he said. “The government has to have some more teeth. It needs to do something different.”

A spokesperson for the Department of Health and Social Care said: “It is absolutely right that patients should have access to cost-effective, innovative medicines on the NHS at a price we can afford.

“Despite being offered in the region of £500m over five years – the largest ever commitment of its kind in the 70-year history of the NHS – Vertex has refused to accept, putting Orkambi out of reach of patients.

“We’re aware there may be other avenues open to resolve this issue, but our approach remains urging Vertex to accept NHS England’s generous offer.”

The House of Commons health and social care select committee has launched an inquiry into the availability of Orkambi and will hold a public hearing in March. In a letter to the committee last month, NHS England’s national director of specialised commissioning, John Stewart, said: “If companies like Vertex continue to price products significantly above the value they bring, then the situation is unsustainable. Vertex is an extreme outlier in terms of both its pricing and behaviour.”

He added: “The prices being demanded by Vertex don’t come close to meeting the cost-effectiveness thresholds that all other companies are working towards.”

Vertex, in its 16 January letter to the committee from the company’s European president, Simon Lem, said: “As long as Nice remains constrained by its current approach to the technology appraisal process, and, ultimately, by the budgetary limits set by the Department of Health and Social Care, it is unlikely that the parties will arrive at an outcome that grants access to our treatments for CF [cystic fibrosis] patients in England.”

The company declined to answer questions from the Guardian. Portland, its public relations consultancy, said Vertex would be participating in the public hearing.

It said: “Out of respect for the parliamentary process, we will not be providing further updates at this time. Vertex welcomes the committee’s interest in access to cystic fibrosis medicines and we look forward to continuing to support its inquiry into this important issue.”

The company has responded to an open letter by campaigners who wrote on behalf of their children suffering with the disease. The company said it reinvests nearly 70% of its revenue back into its research, which has allowed it to discover medicines like Orkambi.”

It said: “Precision therapies like ours are delivering unprecedented results, but they also present new economic challenges. We recognise fully the constraints that health systems around the world are working under, which create unenviable choices for the health authorities.”

Health authorities “need to adapt their systems to the realities of modern medicine,” the letter went on.

“Vertex shares the responsibility with governments and regulators to do all that we can to agree to a fair price that reflects the value of these medicines in all countries where they are needed.”

There are more than 10,000 people with cystic fibrosis in the UK and half could benefit from Orkambi because they have the particular genetic defect that the drug targets. Vertex’s newer, similar drugs are likely to help even more.

The price of the drug has caused consternation around the world. In the US, Orkambi costs $272,000 (£207,000) per patient, per year, which is not affordable for those without good medical insurance. In Canada, where the drug costs the equivalent of £146,000, patients have launched a class action in the courts against the government for access to it.