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New AIDS medication ready for clinical trial

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Raltegravir (MK-0518) and Maraviroc ready for clinical trials.

LOS ANGELES, Feb. 28 – UPI reports that two new drugs appear to give patients who are running out of medical options potent weapons against advanced, resistant infection with the virus that causes AIDS.

After years of therapy affected individuals are infected with virus strains that have developed resistance to almost all classes of drugs designed to fight AIDS. “Yet when these patients were given Raltegravir, 61 percent of them were able to reduce viral levels in the blood to undetectable levels,” said Roy Steigbigel, professor of medicine at the State University of New York Stony Brook Health Sciences Center, told United Press International. “That compared to 5 percent of patients with the same background of drugs who did not receive raltegravir.”

Raltegravir the first of a new class of substances, called integrase inhibitors, and is being developed by Merck. In earlier studies, the drug was known as MK-0518. It knocks out one of the three enzymes of the HI virus that is required for viral replication. (So far only drugs to inhibit the other enzymes, protease and reverse transcriptase, have been in use.) hiv-maturhiv.gif

In two phase 3 trials, raltegravir delivered along with the best combination of other drugs available proved clearly superior to the best optimized treatment without raltegravir. Overall, said David Cooper, director of the National Centre in HIV Epidemiology and Clinical Research in Sydney, Australia, 77 percent of the 232 patients in his BENCHMARK-1 trial achieved an undetectable viral load after 16 weeks of treatment, compared with 41 percent of 118 patients who did not receive the experimental drug.

In BENCHMARK-II, the results mirrored Cooper’s trial: 77 percent of 230 patients on raltegravir achieved an undetectable virus, compared with 43 percent of 119 patients on the best available care without raltegravir. When raltegravir was combined with two newly approved agents, the injectable fusion inhibitor enfuvirtide (Fuzeon, also known as T-20) and darunavir (Prezista), about 98 percent of patients were able to reach undetectable virus levels.

Researchers reporting phase 3 trials of Pfizer‘s experimental drug Maraviroc found similar results in similarly designed trials. Pfizer reports, that the results of MOTIVATE I and II showed that about 60 percent of 426 patients taking maraviroc were able to lower viral levels to undetectable compared with less than 30 percent of 209 patients on optimized background treatment.

Maraviroc is, as such, the first CCR5 inhibitor to be tried clinically. CCR5 is one of two receptors used by the virus as gateways into cells, where the virus then begins its replication. Research has determined that undetectable viral levels — although not a cure — slows viral replication to the point where the virus has less chance of mutating and developing resistance to the drugs. There does exist another door lock on the cell surface: the CXCR4 receptor. Some individuals have exclusively CCR5 receptors; others have both CCR5 and CXCR4 receptors. In the maraviroc trials, all the patients had CCR5 receptors.


These new drugs still require Food and Drug Administration approval before they will be widely available, and for good reason. Whereas integrase is located in the virus exclusively, CCR5 is a natural part of the surface of human cells. Knocking it out has for sure consequences for the interaction of those cells, mostly defendors in the immune system. It takes no effort to imagine, both meds, als all new substances tried in medicine, should kindle not only hope but awareness too, as of the expectable side effects, which are completely unknown so far.



Written by huehueteotl

February 28, 2007 at 10:34 pm

3 Responses

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