he Proton Therapy Center in the Czech capital said the boy was likely to go there after the weekend.
Parents Brett and Naghemeh King removed Ashya from Southampton General Hospital on 28 August after disagreeing with doctors about his treatment.
They were later arrested in Spain under a European Arrest Warrant.
Ashya was made a ward of court at the request of Portsmouth City Council, but the court ruled that status would end when he arrives at the Proton Therapy Centre in Prague.
The clinic said they “do not expect” Ashya to arrive over the weekend, with Monday being the likely earliest time he would arrive.
A spokesperson for University Hospital Southampton NHS Foundation Trust said: “Today’s judgement will allow Ashya to get the treatment he urgently needs without any further delays.
"Throughout the period that we cared for Ashya and over the last few days, our only interest has been his health, medical treatment and welfare.
"We will continue to support any clinicians involved in his future care with advice and information."
Lawyers representing the Kings had earlier been discussing his case at the High Court in a hearing conducted by telephone and involving UK and Spanish lawyers.
Mr Justice Baker approved a treatment plan after telephone discussions with legal teams representing both Mr and Mrs King and Southampton General Hospital.
The judge was told - on Tuesday - that Mr and Mrs King wanted their son to receive proton beam radiotherapy.
A lawyer representing hospital bosses said doctors aimed to provide chemotherapy but not proton beam therapy. Vikram Sachdeva said such treatment could not be provided in Britain.
The highly poisonous substances were found in a hunt triggered by the accidental discovery in July of vials of smallpox at a lab in the National Institutes of Health near Washington.
They included vials of ricin and pathogens that cause botulism, the plague and a rare tropical infection.
The substances, some dating from nearly a century ago, have now been destroyed.
Officials from the National Institutes of Health (NIH) said some of its laboratories were cleared to use poisonous substances and were checked regularly.
But the recent finds were from historical collections that were once allowed to be stored without regulation.
They included a bottle of ricin, a highly poisonous toxin, found in a box with microbes thought to be 85 to 100 years old.
"NIH takes this matter very seriously. The finding of these agents highlights the need for constant vigilance in monitoring laboratory materials in compliance with federal regulations on biosafety,” a memo from the agency said.
The authorities said the newly discovered toxins had been improperly stored but were in sealed containers and no employees were in danger of infection.
The search for unregulated toxic substances was initiated after the discovery of long-forgotten vials of smallpox in July.
The virus, believed dead, was located in six freeze-dried and sealed vials. It was said to be the first time unaccounted-for smallpox has been discovered in the US.
The disease was officially declared eradicated in the 1980s.
The Jamaican Defence Force said the plane went down about 14 miles (22km) north-east of Port Antonio.
The US had earlier scrambled two F-15 fighter jets when the plane failed to respond to air traffic control.
The two people known to be on board have been named as Larry Glazer, a property developer from Rochester, New York, and his wife Jane.
The couple were both licensed pilots.
Major Basil Jarrett of the Jamaican Defence Force told reporters that an oil slick had been spotted off the coast but there was no sign yet of any wreckage.
He said search and rescue teams were scouring the waters for possible survivors.
The plane, a Socata TBM-700 built in 2014, took off from Rochester at 08:26 (12:26 GMT) en route to Naples, Florida.
The North American Aerospace Defence Command (Norad) was alerted to the unresponsive plane about an hour into its flight and sent two fighter jets to monitor it.
A spokesman said it was not possible for the fighter pilots to see inside the plane as the windows were frosted or fogged over.
A tweet from Norad suggested the pilot or pilots could have been be unresponsive due to “possible hypoxia” - oxygen deprivation.
The plane had been flying at an altitude of 25,000ft (7,600m) southbound over the Caribbean Sea, approaching the north east point of Jamaica, when it went off radar.
New York Governor Andrew Cuomo paid tribute to the couple.
"The Glazers were innovative and generous people who were committed to revitalising downtown Rochester and making the city they loved a better place for all," he said.
The couple’s three children said in a statement they were “devastated”.
Earlier, the US Federal Aviation Administration said it has co-operated with Cuba air traffic control in monitoring the plane, despite the countries not having full diplomatic relations for more than half a century.
From 18 to 21 September people will not be allowed to leave their homes, a senior official said.
The aim of the move is to allow health workers to isolate new cases to prevent the disease from spreading further.
The outbreak has killed about 2,100 people in Sierra Leone, Liberia, Guinea and Nigeria in recent months.
The World Health Organization announced on Friday that health workers could be given vaccines as from November, when safety tests are completed.
More than 20 health workers have lost their lives to the virus in Sierra Leone since the start of the outbreak in March.
Last month Liberia sealed off a large slum in the capital Monrovia for more than a week in an attempt to try to contain the virus.
The disease infects humans through close contact with infected animals, including chimpanzees, fruit bats and forest antelope.
It then spreads between humans by direct contact with infected blood, bodily fluids or organs, or indirectly through contact with contaminated environments.