Today, AIDS is not the bulletproof killer it appeared to be in the 1980s. Current treatments for those infected by the human immunodeficiency virus (HIV), known collectively as Highly Active Antiretroviral Therapy (HAART), have not destroyed the beast, but they have certainly tamed it. Although the infection still claims thousands of lives every year, for the majority of HIV-positive patients it is now a controllable chronic condition.
Yet, while significantly decreasing mortality, HAART is plagued with complications that run the gamut from issues of toxicity and resistance, to patient compliance and adherence to treatment regimens. Nevertheless, PRO 140 from CytoDyn Inc. (OTCQB: CYDY) holds the promise of resolving those issues. PRO 140 is a humanized monoclonal antibody for HIV treatment that, in trials, has shown no serious side effects and hardly any toxicity in over 200 patients.
HAART, in use since 1996, is a combination of different classes of medications that is prescribed based on such factors as the patient’s viral load (how much virus is in the blood), the particular strain of the virus, the CD4+ cell count, and other considerations, and it is designed to slow the rate at which the HIV makes copies of itself. The HIV life cycle, or replication process, takes place in seven stages and particular drugs interfere with the process by attacking one of those stages. HAART, being a ‘cocktail’ of drugs, attacks on several fronts at different stages in the HIV development process.
Various HAART regimens are currently recommended by the U.S. National Institutes of Health (http://nnw.fm/p2iPW). However, because HAART cannot rid the body of HIV, it must be taken every day for life, and that is a tall order for most patients. Consequently, one flaw of HAART is a lack of ‘medication adherence’, or patients not taking HIV medication every day and as exactly as prescribed.
A common reason for this failure to follow doctor’s order is that the drugs used in HAART can be intensely toxic, to the point of being life threatening, with the prescription, in some cases, being just as bad as the malady. Drug resistance further complicates HIV regimens, although, since HAART is a mix of drugs, there is usually less chance of patients developing resistance.
Unlike HAART, which works to slow HIV replication by inhibiting viral enzymes within cells already affected by HIV, a new class of drugs, known as viral entry inhibitors, is being developed to protect healthy cells from HIV infection by blocking early steps in the viral life cycle. PRO 140 works by attaching to the same portion of the CCR5 co-receptor to which HIV normally binds and by blocking the HIV from attaching to the CCR5 co-receptor, thus denying the virus entry.
This mechanism offers distinct advantages over HAART. The normal function of CCR5 is to bind chemokines, or molecules that regulate inflammation. Other HIV drugs that target CCR5 interact with the pocket of the receptor and thereby inhibit binding of both HIV and chemokines, which may have a number of adverse consequences because of the disruption of the chemokine inflammatory response. However, PRO 140 blocks HIV, yet permits normal chemokine binding, potentially leading to less side effects.
Early clinical testing indicates that PRO 140’s half-life contributes to the masking of CCR5 receptors for up to two months. Thus, infrequent dosing with PRO 140 may be possible compared to small molecule drugs, which require daily dosing.
In addition, being an antibody and not a synthetic drug means that PRO 140 will likely (as it has demonstrated in past clinical trials) have fewer issues with toxicity. In addition, previous short- and long-term trials (as long as 2.5 years) have shown that PRO 140 is less likely to induce the development of resistant viruses.
Last December, CytoDyn Inc. announced that several patients had been treated in the first Phase III clinical trial with PRO 140 as a single-agent maintenance therapy in virally suppressed subjects with HIV. PRO 140 is considered one of the most advanced experimental monoclonal antibodies for HIV treatment and has been used in more than 140 HIV-infected subjects in placebo-controlled and open label FDA-approved clinical trials. The drug has been the subject of seven clinical trials, each demonstrating efficacy by significantly reducing or controlling HIV viral load in human test subjects, and it has been designated a “fast track” product by the FDA.
In January, CytoDyn filed a request for Breakthrough Therapy Designation with the FDA for PRO 140 as a treatment for HIV-1 infection in treatment-experienced patients with virologic failure.
For more information, visit www.CytoDyn.com
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