Judges at the European Court of Human Rights have rejected a plea from the parents of terminally-ill baby Charlie Gard to intervene in his case.
Chris Gard and Connie Yates lost their final legal bid to take their son to the US for treatment.
Specialists at Great Ormond Street Hospital believe Charlie has no chance of survival.
The court agreed, concluding that further treatment would "continue to cause Charlie significant harm".
Charlie is thought to be one of 16 children in the world to have mitochondrial depletion syndrome, a condition which causes progressive muscle weakness and brain damage.
His parents had previously seen a Supreme Court challenge to continue Charlie's life support fail.
European Court judges have now concluded it was most likely Charlie was "being exposed to continued pain, suffering and distress" and undergoing experimental treatment with "no prospects of success... would offer no benefit".
They said the application presented by the parents was "inadmissible" and said the court's decision was "final".
The court "also considered that it was appropriate to lift the interim measure" which had required doctors to continue providing life support treatment to Charlie.
BBC health correspondent Fergus Walsh said it is likely Charlie's life support machine will be turned off within a few days following discussions between the hospital and his family.
Charlie Gard: Timeline of parent's legal battle:
- 3 March 2017: Mr Justice Francis starts to analyse the case at a hearing in the Family Division of the High Court in London
- 11 April: Mr Justice Francis says doctors can stop providing life-support treatment
- 3 May: Charlie's parents ask Court of Appeal judges to consider the case
- 23 May: Three Court of Appeal judges analyse the case
- 25 May: Court of Appeal judges dismiss the couple's appeal
- 8 June: Charlie's parents lose fight in the Supreme Court
- 20 June: Judges in the European Court of Human Rights start to analyse the case after lawyers representing Charlie's parents make written submissions
- 27 June: Judges in the European Court of Human Rights refuse to intervene
Charlie's parents, from Bedfont, west London, raised £1.3m on a crowdfunding site to pay for the experimental treatment in the US.
Ms Yates had already indicated the money would go towards a charity for mitochondrial depletion syndromes if Charlie did "not get his chance".
"We'd like to save other babies and children because these medications have been proven to work and we honestly have so much belief in them.
"If Charlie doesn't get this chance, we will make sure that other innocent babies and children will be saved", she said.
Great Ormond Street Hospital said the decision marked "the end of what has been a very difficult process" and its priority was to "provide every possible support to Charlie's parents as we prepare for the next steps".
"There will be no rush to change Charlie's care and any future treatment plans will involve careful planning and discussion," a hospital spokesman said.
In April a High Court judge ruled against the trip to America and said Charlie should be allowed to die with dignity.
Three Court of Appeal judges upheld the ruling in May and three Supreme Court justices dismissed a further challenge by the parents.