A doctor from NY has agreed to travel to the United Kingdom next week to examine 11-month-old Charlie Gard, whose parents are fighting a legal battle to allow them to take the baby to the US for an experimental treatment.
But Dr Hirano, 55, believes his experimental theory could give Charlie "11% to 56% chance of clinically meaningful improvement".
Earlier this month New-York Presybterian Hospital/Columbia University Irving Medical Center offered to admit Charlie and to provide him with experimental treatment, according to the Washington Post.
Hirano says the therapy he is developing could improve the condition of Charlie who suffers from a form of mitochondrial disease.
Hirano is one of the pioneers of nucleoside - an experimental therapy which is being sought by Charlie's parents, Chris Gard and Connie Yates.
Chris Gard and Connie Yates have clashed with doctors
The mother, Connie Yates, told the Press Association that doctors at Great Ormond Street wanted to turn off Charlie's life-support but decided not to after the White House intervened. The case attracted worldwide attention after Pope Francis and President Donald Trump weighed in.
Great Ormond Street had said Charlie's mechanical ventilator would be switched off after the European judgment, but the hospital has since given the boy's parents more time to spend with him before this happens.
Hirano, who has been providing evidence to the High Court via video link, suggested that now, there is clinical data that were not available in April, and he thought the therapy was "worth trying".
"In my view my keeping Charlie on artificial ventilation will not cause significant harm because he does not seem to be in pain", he said.
Rare-disease specialists at Bambino Gesu' are working with other global experts to map out an experimental treatment protocol for Charlie, hospital chief Mariella Enoc said.
The Vatican said Pope Francis was following the case with "affection and emotion" and "expresses his own closeness to his [Charlie's] parents".