Lawyers for Aleksanyan, 36, had appealed a lower court's ruling last month ordering their client to remain jailed while he awaits trial on embezzlement and money laundering charges.
After an emotional speech by Aleksanyan's lawyer, Yelena Lvova, and brief arguments from the prosecution, judges Yevgeny Naidyonnov, Natalya Smirnova and Yelena Panarina ordered Aleksanyan to remain under guard while being treated at a local clinic.
"This court has deliberately and repeatedly refused to admit evidence that would provide grounds to free Aleksanyan so he can receive proper treatment," Lvova told the court.
Aleksanyan was not in the courtroom Wednesday because of his deteriorating health, and the ruling means he will likely die before his case comes to trial, Lvova said.
Lead prosecutor Nikolai Vlasov said after the hearing that he was "satisfied" with the decision.
"The defense has been playing on the emotions of the court, but the law has won. That's all," Vlasov said.
Aleksanyan has said he was denied AIDS treatment while in detention because he had refused to testify against his former Yukos bosses, Mikhail Khodorkovsky and Platon Lebedev, who face new fraud and tax-evasion charges on top of the eight-year prison sentences they are already serving.
The European Court of Human Rights had repeatedly called on Russian authorities to transfer Aleksanyan to a specialized AIDS clinic.
Prosecutors argued Wednesday that Aleksanyan is a flight risk and that he could tamper with evidence or influence the proceedings if he were released from custody.
Lvova argued that the investigation into Aleksanyan's purported embezzlement crimes was already completed, meaning that there was no one for him to influence and no new evidence to tamper with.
"This is a person whose primary concern is to fight for his life," she said.
In a telephone interview Wednesday evening, Lvova said she had visited Aleksanyan in the hospital and that he took the news of Wednesday's ruling "very badly."
"He is very upset, but he is courageous," she said, adding that her client wanted to appeal to the Supreme Court to secure his release.
One guard is stationed next to Aleksanyan's bed and another outside his room, Lvova said. A third guard in an adjacent room is monitoring Aleksanyan via closed-circuit television, and his door is locked when he is left alone, she said.
Doctors say Aleksanyan is not responding well to medication that would allow him to recover enough to undergo much-needed therapy, Lvova said.
Aleksanyan was detained in April 2006 and had been held in the Matrosskaya Tishina pretrial detention facility before being moved to the unidentified clinic on Feb. 8.
A week after his transfer his lawyers said they were shocked to find him handcuffed to his bed. A Federal Prison Service spokesman, Valery Zaitsev, said regular clinics lacked proper security to handle prisoners, hence Aleksanyan's handcuffing.
His lawyers say he is no longer chained to his bed.
A Message from The Moscow Times:
Dear readers,
We are facing unprecedented challenges. Russia's Prosecutor General's Office has designated The Moscow Times as an "undesirable" organization, criminalizing our work and putting our staff at risk of prosecution. This follows our earlier unjust labeling as a "foreign agent."
These actions are direct attempts to silence independent journalism in Russia. The authorities claim our work "discredits the decisions of the Russian leadership." We see things differently: we strive to provide accurate, unbiased reporting on Russia.
We, the journalists of The Moscow Times, refuse to be silenced. But to continue our work, we need your help.
Your support, no matter how small, makes a world of difference. If you can, please support us monthly starting from just $2. It's quick to set up, and every contribution makes a significant impact.
By supporting The Moscow Times, you're defending open, independent journalism in the face of repression. Thank you for standing with us.
Remind me later.