The Crown Prosecution Service says it has stopped proceedings against Ashya King's parents after evidence received today indicated they were not guilty of "wilful neglect" of their child by taking him from hospital care.
The CPS said initial evidence showed Ashya needed "round-the-clock nursing care", including some which required training and specialist nutrition that it believed Brett and Naghmeh King did not have.
However, the CPS said it now believed Mr and Mrs King took "certain steps to safeguard the health of Ashya" after new evidence today.
It said evidence from two independent medical experts also "indicated that the risk to Ashya's life was not as great or immediate as had been originally thought".
Therefore the charge of child cruelty supported by wilful neglect could not be proved to the required standard, the CPS said.
The head of the police force which applied for a European Arrest warrant against the parents of Ashya King has now urged their release.
A British mother whose son's life was saved by proton therapy has told ITV that she defied NHS doctors' advice to pursue the treatment.
The parents of Ashya King said they took him out of a hospital to seek proton beam treatment which is not available under the NHS.