Great Ormond Street Hospital has applied for a fresh court hearing in the case of terminally-ill baby, Charlie Gard, following claims of "new evidence relating to potential treatment for his condition".
Seven medical experts, including the US doctor who has offered to treat Charlie, wrote a letter to the hospital suggesting unpublished data could help cure the 11-month-old's brain damage. In it they explain that the treatment would be experimental for Charlie's particular condition.
They claim that "ideally" the treatment would first be tested on mice but state that, in Charlie's case, there is not time for such a trial.
Previously, the High Court said it was unlikely the US doctor offering to treat Charlie would be able to cure him.
The hospital has said it would "explore" the data.
A hospital spokesman said: "Two international hospitals and their researchers have communicated to us as late as the last 24 hours that they have fresh evidence about their proposed experimental treatment.
"We believe, in common with Charlie's parents, it is right to explore this evidence. Great Ormond Street Hospital is giving the High Court the opportunity to objectively assess the claims of fresh evidence.
"It will be for the High Court to make its judgment on the facts.
"Our priority has always been, and will always be, the best interests of Charlie Gard," continued the spokesman.
Under a High Court ruling, Great Ormond Street Hospital is forbidden from allowing Charlie to be transferred for nucleoside therapy anywhere.
Charlie's case will be heard by Mr Justice Francis on Monday at 2pm, according to a High Court listing.
Signatories to the new letter include a scientist from Cambridge University's Mitochondrial Biology Unit and two researchers from Vall d'Hebron Institut de Recerca in Barcelona and a neurologist and a research fellow from Rome Children's Hospital, Bambino Gesu.
Meriella Enoc, the head of the Vatican's pediatric clinic at Bambino Gesù, said on 3 July that they would be willing to welcome Charlie Gard "for as long as he lives.
The Vatican hospital stepped in after Pope Francis called for the Charlie's to be allowed to do accompany and care for their child "until the end". A Vatican statement on 2 July also said that the pontiff is following Charlie’s case with “affection and emotion”.
Foreign Secretary, Boris Johnson, has said it is impossible for terminally ill Charlie Gard to be transferred to the Vatican's children's hospital for treatment.
Charlie, who is ten months old, has a rare genetic condition, mitochondrial depletion syndrome, that causes progressive muscle weakness and brain damage and doctors want to stop his life support. They say he can not see, hear, cry or swallow and is only breathing with the help of a ventilator.
Chris Gard and Connie Yates, from south west London, believe their son should undergo experimental medical therapy in the United States which they hope will prolong his life. Their son has been in intensive care at London’s Great Ormond Street Hospital since last October. Specialists at the hospital say the experimental treatment would not help.