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New Report Finds A Variety Of New HIV Drugs And Vaccines Under Development

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Published: Dec 14, 2010 1:57 pm
New Report Finds A Variety Of New HIV Drugs And Vaccines Under Development

United States pharmaceutical companies have a total of 40 new antiretrovirals, three possible gene therapy treatments, and several therapeutic vaccine candidates under development for treatment of HIV, according to a new report from the Pharmaceutical Research and Manufacturers of America.

The Pharmaceutical Research and Manufacturers of America (PhRMA), a pharmaceutical company lobbying group, releases a report each year on HIV treatments under development at U.S. pharmaceutical companies. The report this year includes new antiretrovirals, gene therapies, and vaccine candidates, in addition to treatments for HIV-related conditions such as Kaposi’s sarcoma and peripheral neuropathy (pain or numbness in the extremities).

Most of the new antiretrovirals are still in Phase 1 or Phase 2 clinical trials. The list includes novel drug types that work differently than current anti-HIV drugs, as well as drugs in standard antiretroviral drug classes, such as new protease inhibitors and nucleoside reverse transcriptase inhibitors (NRTIs).

In addition, there are three new combination treatments under development. Combination treatments include several antiretrovirals in one pill, which simplifies treatment regimens.

New Types Of Antiretroviral Drugs

Several of the antiretrovirals in the report are novel drug types that are not part of existing antiretroviral drug classes.

A number of these treatments consist of antibodies, proteins that help the body recognize and fight viruses. These treatments usually work by attempting to stimulate the immune system so that it can more effectively recognize and kill HIV or infected cells. Nearly all of these are still in Phase 1 clinical trials, although one set of antibodies are in Phase 2 trials.

There are a few additional prospective drugs that have made it to Phase 2 trials. One of these is also a protein treatment, called Alferon LDO (interferon alfa-n3). This protein is isolated from human blood and helps fight viral infections; currently it is approved by the U.S. Food and Drug Administration to fight human papillomavirus, which causes genital warts.

Another new treatment, called CB1922, is currently in Phase 2 clinical trials. CB1922 is a drug that has mostly been investigated for treatment of high blood pressure. It works by blocking a protein on the surface of cells that normally binds to a hormone called aldosterone.

Canopus BioPharma, which makes CB1922, has found that HIV also binds to this same protein by mimicking the hormone. By blocking the protein, CB1922 appears to prevent HIV from replicating itself.

Finally, a drug from Bristol-Myers Squibb, called BMS-626529, is also in Phase 2 clinical trials. Bristol-Myers Squibb has not explained the mechanism of BMS-626529, but states that it prevents HIV from attaching to cells, which would prevent infection and virus replication.

New Drugs In Existing Antiretroviral Drug Classes

Most of the new drug candidates are in existing antiretroviral drug classes, including the following two drugs that are in or have completed Phase 3 trials: elvitegravir, which is a new integrase inhibitor from Gilead Sciences, and rilpivirine, a non-nucleoside reverse transcriptase inhibitor (NNRTI) developed by Tibotec Pharmaceuticals.

Integrase inhibitors, such as elvitegravir, are a relatively new class of antiretroviral; currently, the only approved integrase inhibitor is Isentress (raltegravir).

In addition to elvitegravir, there are three new integrase inhibitors under development (GSK1247303, GSK1265744, and GSK1349672). All of these are in Phase 2 clinical trials and were developed by GlaxoSmithKline.

NNRTIs, in contrast, are an older drug class that includes Sustiva (efavirenz), Viramune (nevirapine), and Intelence (etravirine). Including rilpivirine, there are seven new NNRTIs under development; four of these are also in Phase 2 clinical trials (dapivirine vaginal gel, RDEA806, UK-453061, and VRX806).

The list includes seven new NRTIs, which is the oldest antiretroviral drug class and includes drugs such as zidovudine (Retrovir) and Epivir (lamivudine). Four of the proposed new NRTIs (elvucitabine, festinavir, racivir, and amdoxovir) are in Phase 2 clinical trials.

Only two new protease inhibitors (a drug class that includes Prezista (darunavir) and Kaletra (lopinavir/ritonavir)) were included in the report, one of which, TMC310911, is in Phase 2 trials.

Finally, the report includes several new entry inhibitors, which are another fairly new class of antiretroviral that includes the drugs Selzentry (maraviroc) and Fuzeon (enfuvirtide).

Entry inhibitors work by preventing HIV from entering and infecting new cells. Most of the new treatments act the same way as Selzentry, which blocks a protein called CCR5 on the surface of white blood cells that HIV uses to attach to and invade. Two of the proposed new entry inhibitors (PRO-140 and TBR-652) are in Phase 2 clinical trials.

New Combination Drugs

Combining several antiretroviral drugs into one pill has been a growing trend, since it simplifies antiretroviral regimens for patients. There are currently three combination treatments under development.

One, called the “Quad” pill (see related AIDS Beacon news), is a combination of four drugs in one pill: Emtriva (emtricitabine), Viread (tenofovir), and the investigational integrase inhibitor elvitegravir plus a proposed new antiretroviral booster, cobicistat. Cobicistat is thought to act similarly to Norvir (ritonavir) by raising antiretroviral drug concentrations to make them more effective.

A second combination pill will include the new NNRTI rilpivirine plus Emtriva and Viread.

Finally, the third proposed combination pill will include three already approved antiretrovirals: Sustiva (efavirenz), Epivir (lamivudine), and Viread.

Gene Therapy And Vaccines

Aside from antiretroviral drugs, the report includes both gene therapies and therapeutic vaccine treatments as potential new HIV treatments.

Gene therapy treatments are experimental procedures that scientists hope will one day be able to cure HIV (see related AIDS Beacon news). They work by changing a person’s genes, for example by turning off genes that produce proteins used by HIV to infect cells.

Three gene therapy treatments are currently under development, two of them in Phase 1 trials and one in Phase 2.

Two of the treatments work by inserting genes that make genetic material that binds to and neutralizes HIV’s genetic material so that it no longer functions. One of the treatments is being developed by the biotechnology company VIRxSYS and is currently in Phase 1 trials. The second one by Enzo Biochem is currently in Phase 2 trials.

The third therapy, by Sangamo Biosciences, works by preventing cells from producing the CCR5 protein on their surface, preventing HIV from infecting the cells in much the same way Selzentry does.

Finally, there are a number of therapeutic vaccines also under development (see related AIDS Beacon news). Therapeutic vaccines enhance the body’s natural immune response, helping to control HIV in people already infected with the virus.

Most of the therapeutic vaccines are in Phase 1 clinical trials. However, there are a few that are in Phase 2.

One of these is a dendritic cell vaccine by Argos Therapeutics. Dendritic cell vaccines are made by collecting blood from patients and isolating a certain type of immune cell called a dendritic cell.

After exposing the dendritic cells to HIV proteins in the laboratory to prompt an immune response, the cells are reinjected into the study participant in hopes that the cells will now be activated and fight against HIV.

Two other therapeutic vaccines that are in Phase 2 clinical trials are the DermaVir vaccine, by the company Genetic Immunity, and Vacc-4x by Bionor Pharma (see related AIDS Beacon news).

The DermaVir vaccine is applied as a patch rather than an injection and attempts to limit virus replication. Vacc-4x, in contrast, contains protein fragments similar to those found within the HIV virus, in an attempt to enhance the ability of patients’ immune systems to recognize and kill HIV-infected cells.

For more information, please see the report from PhRMA. For more information on clinical trials, please see the United States Clinical Trials Registry.

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