On July 23, the Food and Drug Administration will make its decision on bezlotoxumab, brand name Zinplava, a Merck & Co., Inc. (NYSE:MRK) monoclonal antibody drug designed to prevent recurrence of C. difficile infection. Market Exclusive’s Inside the FDA series will attempt to give you an inside look at the FDA’s decision making process, its leanings and deliberations, and deduce from there the chances of a given drug’s approval. We will be using FDA briefing documents straight from the agency itself to give our readers a more accurate picture of what is going on.
From there we will summarize market potential and make a brief investment analysis based on the chances we estimate from the FDA briefing documents themselves. This week we will begin with Merck.
C. difficile Infection Background
C. difficile infection is essentially a man-made disease that results from an imbalance in gut bacteria, usually as a result of long courses of antibiotics that disturb the internal microbiome. The microbiome is the community of bacteria in the intestine, most of which are either harmless, helpful, or even essential for digestion. C. difficile is a bacteria that is present in most people and usually harmless. It is kept in check by other bacterial colonies in the gut that compete with it for resources. However, when long courses of antibiotics are taken, especially antibiotics that are broad spectrum and kill many types of bacteria, C. difficile can quickly take over and overpopulate the gut, causing anything from diarrhea to life threatening holes in the intestinal wall.
Think of it as a predator-prey situation. If the predator is taken out of an ecosystem, the prey can often overpopulate the area and cause widespread destruction. Both predator and prey keep the ecosystem in balance.
The danger of C. difficile infection is not from the bacteria itself, but from the toxins it produces as byproducts that cause inflammation in the intestinal wall. Much like necrotizing fasciitis, or flesh-eating bacteria, it is not the bacteria itself that eats flesh but a toxin produced by the bacteria that causes the symptoms.
Bezlotoxumab is not an antibiotic, but an antibody that is designed to lock onto C. difficiletoxin B, which is theorized to cause intestinal inflammation. The elderly who are under long term hospitalization and antibiotic treatment are the highest risk group, as the most virulent strains originate in hospitals where antibiotics are common. Data published in 2009 reported 336,600 hospitalizations in the US from C. difficile infection (CDI), and as antibiotic use and resistance grows, those numbers have grown as well.
As of 2011 according to the U.S. Centers for Disease Control and Prevention (CDC), CDIinfections numbered half a million with 29,000 deaths often within 30 days of initial diagnosis, so this is serious stuff and not just a painful nuisance like your average intestinal bug and diarrhea episode. In the U.S., 80% of deaths related to CDI occur in patients 65 or older.
The infection itself is treated, once again, with antibiotics as there currently is no other choice. Bezlotoxumab is designed to prevent the recurrence of infection after an initial cure by antibiotics. An FDA panel back on June 9 voted 10 to 5 to recommend the drug for approval, which is generally seen as a shoe-in for approval, but the FDA briefing document is not as simple as that. So let’s get into it.