A US doctor offering experimental treatment to a critically ill British baby is due in London this week to help persuade a judge to keep the boy's life support switched on.
The parents of Charlie Gard, who has a rare genetic condition causing progressive muscle weakness and brain damage, have been fighting a legal battle to send him to the United States for the neurologist's experimental therapy.
But Britain's courts have refused permission on the grounds it would prolong his suffering without a realistic prospect of it helping, prompting a fierce debate around the world about medical ethics.
The case has gained global attention after interventions by US President Donald Trump and Pope Francis, who both voiced support for 11-month-old Charlie on Twitter.
It has prompted a heated debate about whether the hospital treating the child or his parents should determine his fate.
The US doctor offering the treatment, Michio Hirano, a professor of neurology at New York's Columbia University Medical Center, is due in London to examine Charlie for the first time and to meet other medical experts involved in the case.
Hirano says the therapy he is developing could improve the condition of Charlie who suffers from a form of mitochondrial disease.
He believes there is between an 11 and 56 percent chance the nucleoside therapy would improve the baby's muscular strength and that there is a "small but significant" chance it would also help brain function.
London's world-renowned Great Ormond Street Hospital for Children says Charlie, who cannot breathe without a ventilator, has no quality of life and that his life support should be turned off.