Vertex's VX-765 holds promise for HIV treatment

What do HIV, epilepsy and cellular suicide have in common? Vertex Pharmaceuticals (VRTX 1.43%). More specifically, VX-765.

In a recent report in the journal Science researchers at University of California, San Francisco and the Gladstone Institute of Virology and Immunology found that most CD4 T-cells aren't killed by the HIV virus directly, but by the body's cellular "suicide response" via a protein called caspase-1 (or interleukin-1 converting enzyme) and stopping this process prevents the progression of HIV to AIDS. What's more, the researchers showed that this suicide process is specifically inhibited by Vertex Pharmaceutical's caspase-1 inhibitor VX-765. If that amalgam of letters and numbers sounds familiar, it's because back in 2011 VX-765 failed clinical trials to treat epileptics, but was deemed safe for ingestion by humans. The latter part of this early failure is crucial as it suggests VX-765 can start human trials as an HIV therapeutic rather quickly.

How it works?

Biologically, HIV virus leads to the death of infection-fighting immune cells, called CD4 cells, which results in a massive inflammatory response.  Interestingly, HIV does not directly kill CD4 cells, but instead activates the host cell's "suicide response" via caspase-1, a process known as pyroptosis. The researchers discovered that HIV-infected human tonsils and spleens treated with VX-765 (a caspase-1 inhibitor) prevented death of CD4 cells and dramatically decreased the inflammatory response associated with infection. After treatment with VX-765, the cells showed no signs of progression to active infection. Because VX-765 targets the host cell's own caspase-1, the HIV virus is less-likely to mutate its genome and become resistant to VX-165.

Current State of HIV therapy

One of the biggest players in HIV therapy is actually a joint venture between Pfizer (PFE 1.00%) and GlaxoSmithKline (GSK 2.11%) called Viiv Healthcare. Viiv Healthcare developed lamivudine and zidovudine, two of the most commonly used drugs for HIV therapy and part of multiple drug cocktails: Combivir,  Zeffix, Epirvir, and Trizivir to name a few. In total, ViiV has 11 marketed HIV drugs that all have a similar mechanism of action, that is, attacking aspects of the HIV virus. Abbott Laboratories (ABT -0.20%)is a another significant player in this market with their lopinavir and ritonavir combination drug, Kaletra patented through 2016. Kaletra sales generated $763 million in Q1-Q3 2012 which was down from $882 million in 2011, due to the quadrupling in price of ritonavir. Like ViiV, Abbott's Kaletra works on the premise of attacking the biology of the HIV virus.  

Attacking the biology of the virus has become the standard of therapy for HIV with little innovation out of this schema. During the short-term, this therapeutic strategy may prove effective in decreasing the virion load, but the HIV genome mutates rapidly and can overcome sensitivity and become resistant to these drugs. In fact, resistance occurs in all currently available antiretroviral drugs. This is a huge problem in the fight against HIV, with currently no good solution.

Is VX-765 a first-in-class HIV drug?

Unlike any antiretroviral drug on the market, VX-765 inhibits the body's own caspase-1 protein, not the HIV virus. At first glance, this may seem like an insignificant point, but this mechanism could make VX-765 one of the most successful HIV therapeutics in history. By inhibiting a host protein, VX-765 makes it nearly impossible for the HIV virus to become resistant to therapy. The virus can make whatever mutations it wants, but to progress to AIDS it needs to activate caspase-1 in CD4 cells. 

In addition to the unique molecular mechanism of action, in 2011, VX-765 was tested in humans as a potential treatment for epilepsy. While the drug failed to treat epileptics, the six-week-long studies suggested that VX-765 is safe in humans. This will certainly help VX-765 once it goes to clinical trials.

How will this affect Vertex shares?

Shares of Vertex won't see a dramatic increase in the short-term as VX-765's use as an HIV drug has only been tested at the pre-clinical level, but it's safe to say that this extremely encouraging data won't go unnoticed. With so many players looking for a blockbuster HIV drug, it's possible that the bigger players like Pfizer or Merck will want to snag VX-765 or partner up with Vertex to bring the drug to market as a stand alone therapy or as part of the numerous drug cocktails currently available. A novel drug with the potential to effectively treat HIV with a low risk of treatment resistance might be the biggest selling drug of all time.

With Vertex you have a stock that has the long-term potential of an approved drug in a therapeutic area that is difficult to treat. HIV is a tragic global epidemic with over 70 million infections and 35 million deaths. Our current arsenal of antiretrovirals has proved to be only moderately effective against this devastating disease. Vertex's VX-765 may be an unstoppable weapon in our fight against this disease and investors would be wise to keep an eye on this drug. The company also has another drug in development for the treatment of cystic fibroris, and more clinical trial data should be released this year.

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