Pharma’s Cutting Edge

This is destined to be one of the key HIV papers of this decade, if not longer.

–Robert Gallo

I’m a real fan of unconventional thinking and scientists who are unafraid of venturing outside of their comfort zones.  So, when I read the story of the discovery of new potential drug targets against HIV in Science recently, I was thrilled.  I believe the full article behind the news piece requires a subscription; if you have one it’s worth at least a quick read-through.

Stephen Elledge is a pioneer in the use of “forward genetics” to screen for host factors that influence (suppress and or promote) the malignant phenotype (see this for an example of his group’s creative scientific approach).  In Elledge’s brand of forward genetics applied to cancer target screening, he and his team apply massive pools of interfering RNA to cells of various types to determine whether blocking endogenous gene transcription modulates the malignant cell phenotype. 

In the recent Science paper, Elledge and his collaborators used the same approach with a foreign invader–HIV.  I don’t know whose idea that was, but it was brilliant, and I give Elledge lots of credit for not shying away from a complex, costly, time-consuming HIV study despite his previous lack of experience working with the virus.  In short, the labs grew transformed epithelial cells (HeLa) transfected with some 21,000 pools of siRNAs in pools of 4 siRNAs per gene (i.e. siRNAs against all expressed human genes with transcription-suppresion redundancy to help gaurd against false positives and negatives) and then infected the cells with HIV-1.  When HIV-1 was able to replicate despite host-gene transcription inhibition, the scientists could conclude that the host gene probably wasn’t important for HIV replication, but if HIV replication was disrupted, they could surmise that a host protein involved in HIV replication had been discovered.  As you’ll read, the group found 273 host proteins that HIV relies upon for replication, only 36 of which had been previously discovered, thus explaining how HIV is able to so effectively parasitize its human hosts despite having a genome of just 9000 RNA bases.

As this is a scientific paper, the authors themselves have respectfully avoided aggrandizing this work and their screening approach in general, but this type of study is potentially very clinically relevant in the near-should be a more fruitful strategy to eliminate the virus from the body.  This is because HIV can easily mutate in the face of selection pressure from drugs targeting its own proteins, but it will be much harder for HIV to mutate to circumvent a blockade of a host target (or two) that it requires for reproduction. 

The accompanying news story expresses some skepticism from a Novartis researcher regarding the ease of discovering drugs targeting HDFs and the willingness of pharma to fund such work.  I frankly can’t understand such skepticism, but perhaps the story excerpted the interview in order to provide a bit of contrast to the enthusiasm from Dr. Gallo that opened the piece.  Yes, the HDFs are mostly internal cellular targets, and yes, they probably have some important roles to play in normal host functions, but let’s remember that we already use lots of drugs that fit this description, particularly in oncology, and although side effects are common, so are benefits.  As for pharma funding the work needed to capitalize on this work, let’s remember that it’s one thing to gauge the suits’ interests in the face of established pathway opportunities, and it’s quite another to anticipate their interest in the face of potential therapeutic breakthroughs with large commercial potential.   In my mind, this is a must-do opportunity for any company with virology capabilities and experience.  From a platform perspective, I’d be surprised if most large discovery outfits aren’t already taking advantage of genome-wide functional screening to identify the host factors enabling invaders to live at our expense, whether those invaders be infectious organisms or our own cells gone awry.