The upcoming Conference On Retroviruses And Opportunistic Infections, to be held at the Washington State Convention Center in Seattle from February 13-16, 2017, is billed to feature a heavyweight clash between GlaxoSmithKline (NYSE: GSK) and Gilead Sciences (NASDAQ: GILD) for the treatment of HIV patients (http://nnw.fm/05mzG).
Gilead is expected to present data from mid-stage Phase II testing of bictegravir, an integrase inhibitor similar to GSK’s dolutegravir. The GSK product, marketed as Tivicay, has enjoyed wide success, gaining approval not only in the U.S. but in Canada and the European Union as well. Its success restored GSK’s dominant position in the HIV market, which it had previously lost to Gilead. No doubt, Gilead is hoping to regain the top spot. However, along with Gilead, there is an up-and-coming player in the HIV field.
CytoDyn Inc. (OTCQB: CYDY) is taking its lead product candidate, PRO 140, into Phase III clinical trials. PRO 140 has a number of distinct advantages over competing regimes. Its defensive mechanism is initiated at an earlier stage; it does not interfere with general immune response; and its potential side effects are thought to be much less toxic.
Gilead has been keen to show that bictegravir offers greater potency and reduced side effects than other integrase strand transfer inhibitors (ISTIs), such as Vitekta (elvitegravir), Isentress (raltegravir) and, particularly, Tivicay (dolutegravir). After one study, the company announced that bictegravir had demonstrated superior resistance characteristics. If success along those lines continue, this would allow the drug to be used in combination with others, opening the door to less expensive and more effective treatment regimes.
In devising treatment regimes for HIV, drug resistance is a frustrating stumbling block. Since HIV is a retrovirus, i.e., a RNA-based virus rather than a DNA-based virus, it is subject to copy errors during replication and, consequently, a tendency to mutate rapidly. Although discussed as if it were one virus, the many mutations it undergoes mean that researchers are really dealing with a large population of mixed viruses called quasi-species, some of which, unfortunately, turn out to be resistant to particular drugs.
It gets worse. Sometimes, cross resistance results, meaning that resistance to one drug causes the virus population to become resistant to similar drugs in the same class. It is then possible for someone to be cross-resistant to a drug they have never taken.
However, in previous short-term trials, it has been shown that CytoDyn’s PRO 140 does not induce the development of resistant viruses.
PRO 140 is a viral-entry inhibitor, a new class of HIV/AIDS therapies that work by blocking the entry of HIV to healthy cells. Many of the current AIDS therapies slow HIV replication by inhibiting viral enzymes within cells that are already affected by HIV. However, viral entry inhibitors advance the defense mechanism by protecting healthy cells from being infected in the first place.
PRO 140 is a fully humanized IgG4 monoclonal antibody and thus, unlike a synthetic drug, is likely to have many less side effects. It works by blocking the entry of HIV to CCR5, a molecular portal the virus uses to enter T-cells. However, PRO 140 does not appear to interfere with the normal function of CCR5 in mediating immune responses.
Recently, CytoDyn Inc. announced 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 200 HIV-infected patients 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 patients, and it has been designated a “fast track” product candidate with the possibility of accelerated approval by the FDA.
For more information, visit www.CytoDyn.com
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