] infection as a disease in general. I would characterize this as the original microbiome disease. What I mean by that is there’s a very solid and clear link between the microbiome and 

 infection. It’s been known since roughly 1978 that 

 infections were the most prominent of a class of infection called antibiotic-associated diarrhea. It is what it sounds like. Antibiotics are administered to the patient and the patient develops diarrhea as an adverse effect. Now why is that? We think about the microbiome as being protection in our guts from invasion by host pathogens, 

An analogy I like to use is to think about a really diverse and rich flower garden. We all can see seeds floating on the wind; some of them will occasionally take root, but if you were to clear cut that garden, those roots would have access to the soil. They’d spring up and take over the garden really quickly, and that’s what we see in the gut. The normal microbiome in a healthy gut is like that diverse garden, it has many different colors, flavors, and functions that help the gut function well. But when you damage that through the use of antibiotics for another reason, then you reduce that ability to resist colonization by 

 very often then will come in and take over, proliferate, and cause serious infection.

 itself is a gram positive, anaerobic, spore-forming bacteria. What does all that mean? It’s spore forming, meaning that 

 has the ability to form a very small spore, something like a seed that’s protected from the elements. Because of that, it easily spreads. It can spread through contact and fecal material, and that’s how it gets dispersed throughout a hospital system, which is one of the primary risk areas for 

 is anaerobic. That means that it needs to have an absence of oxygen to grow, and that’s important for its lifecycle. It doesn’t just grow anywhere, it only grows in the absence of oxygen with the exception of when it gets to be that sporiform.

 is able to proliferate in that damaged microbiome, or the damaged garden of the gut, it actually grows, proliferates, and takes over the environment. You had asked about virulence factors—at that point it expresses its primary virulence factors, which are called toxins A and B. Both toxins A and B will cause changes in the shape and function of intestinal epithelial cells. It damages the cells and causes loose injunctions in the intestinal epithelium, which leads to a variety of symptoms, ranging from mild to severe. Milder symptoms are things like diarrhea, bloating, and cramping. More serious symptoms are severe cramping, severe diarrhea, severe intestinal inflammation, also known as toxic megacolon. It can be life threatening.

It’s a serious and very concerning disease, but it also has a lot of quality-of-life issues, particularly when it becomes a recurrent disease. Think about the challenges of being tethered to home. Patients are undergoing an awful lot of symptoms. It affects the quality of life, their ability to function at work and socially. It’s a real challenge for patients, and it’s a real unmet need that we’ve tried to address very early on.

Another aspect that’s very important with 

 infections is the likelihood for recurrence. Many times, roughly 25% of patients who get their first, or primary, 

 infection, are prone to develop a new recurrence of that infection. The reason for that is the standard of care for treating a 

 infection is an antibiotic, which although it kills 

, the bacterium, it also very often damages the gut garden in which 

 has sprung up. Therefore, you’ve killed the weeds, but you still don’t have any flowers there to protect the garden against reseeding and reproliferation of those weeds. When we started Rebiotix Inc in 2011, it was with the recognition that something is needed to replenish that healthy microbiome of the gut. That’s the type of investigational therapeutics that we sought to develop.

Once patients advance to the stage of having a single recurrence, when they’re treated with an antibiotic, they’re very prone to have an additional recurrence. Patients who have a single recurrence will then have a much higher likelihood of having additional recurrences. Fifty percent or more of those patients will develop an additional, and an additional, and an additional 

 infection. It’s a challenge, particularly for the patients and definitely for the health care system as well.

The biggest risk factor is antibiotic, particularly broad spectrum antibiotics, and even more so, antibiotics that inhibit gram positive or anaerobic bacteria. Those are the ones where you’re going to see the highest risk factor. Health care setting is another risk factor, as well as long-term care setting, age, and the immunocompromised. Working downward in priority, all these are certainly risk factors for developing 

 infections, and in many cases, the more risk factors there are, the more likely the patients are to recur as well as contract that first infection.

Clostridioides Difficile Pathogenesis & Manifestation

 What the guidelines recommend for a first episode of 

] is an antibiotic called vancomycin. That’s the most commonly prescribed antibiotic for the first episode. A newer antibiotic approved in 2011, known as fidaxomicin, is also indicated, particularly for the severe first infection. If neither of those are available, then metronidazole, an older 

 antibiotic, would be indicated per guidelines. Once a patient advances to that first recurrence, then the recommendation switches to an additional course of vancomycin, or what’s called a vancomycin taper, which is an interesting concept. It means that we’re going to go in there, treat the patient with vancomycin for several days, and then slowly decrease the vancomycin dosage over several days and space it out. The idea being that we know vancomycin can cause some harm to the microbiome, but if we kill the 

 and then we taper back vancomycin in a way that will keep 

 at bay while allowing some of the microbiome to grow back, then perhaps we can avoid recurrence.

Another antibiotic course that’s recommended for first recurrent 

 is fidaxomicin. It’s generally thought to be more microbiome sparing than vancomycin. That’s why it’s indicated in the first recurrent patients. Once patients have progressed past that first recurrence to multiple recurrent 

, that means that they’re on their second or later recurrence, or they’ve had at least 3 episodes total, then the recommendation goes to strictly a vancomycin taper, or fidaxomicin, or a combination thereof.

The newer guidelines from 2017 also recommend consideration of what’s called a fecal microbiota transplant [FMT]. They do recognize that this is not an approved therapy, but they recognize that there are a lot of data in the literature to suggest it may work. A fecal transplant would be very much what it sounds like. A donor comes to the hospital, they provide a stool sample that’s homogenized into what’s called an FMT, and administered to the patient, usually by colonoscopy. This is done after antibiotic treatment. The idea being, can you add bacteria back into the patient that restores a microbiome that could resist 

 recurrence? It’s important to note that the guidelines recommend that at least 2 courses of antibiotic be considered, and they recognize that this is not yet an FDA-approved treatment.

Managing Recurrent Clostridium Difficile Infections

 I mentioned the concept of fecal transplant. That’s a procedure that’s conducted in the hospital. RBX2660 is an investigational live biotherapeutic. What that means is it’s developed under the guidelines for the FDA, called Investigational New Drug guidelines, which is aiming toward a potentially approvable product that could be marketed as a typical drug. It is a broad consortium investigational live biotherapeutic. That means that in making RBX2660, we try to capture as much of the healthy microbiome, put that in the investigational product, and administer it to patients.

It’s also what we call standardized and stabilized. Those are very important concepts. Standardized means there are good manufacturing practices that allow us to ensure consistency, dose to dose consistency. When a patient gets a treatment with RBX2660, it would be the same no matter when or where they’re getting it. It’s also stabilized, which means that it has a shelf life, the same as any investigational drug would have. You can store it, you can trace it, you can track where it’s shipped, and you can expect that it should meet quality control guidelines to deliver to the patient a consistent dose. That was the investigational product in the trials that we presented about.

The specific trial is called PUNCHCD2. This was a trial conducted a few years ago. It was the first randomized, double-blind, placebo-controlled trial of this type of investigational live biotherapeutic. It was a really exciting trial at the time. We still find it quite exciting and groundbreaking. The question that trial asked was, what is the efficacy of RBX2660 to prevent or reduce recurrence of 

] at 8 weeks after treatment compared to a placebo? That was the concept of the trial and the question we aimed to ask.

We had 3 arms in that trial. We published an interim analysis of that a couple of years ago in which we demonstrated that RBX2660 reduced the recurrence of 

 more than the placebo arm, and that’s highly consistent with the other trials that we’ve run in this space. We’ve run a total now of 5 trials—2 of which are awaiting readout very soon—5 trials in the recurrent CDI [

 infection] space with this investigational product, RBX2660. This trial, PUNCHCD2, showed very consistent response with the other trials.

In addition to that clinical benefit, we also observed a microbiome change from before to after treatment. I’ve introduced the idea that when patients get 

, they have a disrupted microbiome, and what we sought to answer was, have we changed that? Have we provided any restoration toward something more resembling a healthy microbiome? What we saw and published was just that. Among participants who responded to RBX2660, there was a very clear and statistically significant restoration of the microbiome from before to after treatment toward something more resembling a healthy population. We published that last year.

In this study that was presented at ID [Infectious Diseases] Week 2020, we really wanted to take a next step in our translational study and say what effect we have on the metabolome.

We talked a lot about microbiome. The metabolome is all the different functions and metabolites that are being affected by the microbiome. Specifically, in this case we looked at bile acids and the composition of bile acids in the participants’ gut from before to after treatment. Bile acids are interesting to this disease. Typically, our body produces primary bile acids in the liver. Those are converted to secondary bile acids by a healthy microbiome. That’s very important to 

 because the primary acids that the liver produces would normally, if you take those and put them in a test tube, stimulate growth of 

Going back to our garden, they give a growth spurt to 

. But if you have a healthy microbiome, those primary bile acids are quickly converted to secondary bile acids. Again, if we take that and put it in a test tube with 

, we know that those secondary bile acids actually decrease 

. The model that we set out to test is if we have primary bile acids, we would consider that healthier. If we have secondary bile acids, we would consider that less healthy. When we looked at participants from this PUNCHCD2 trial, we found that prior to treatment with RBX2660, they had a preponderance of primary bile acids. That’s not what we consider a healthy balance, but after treatment they rapidly and progressively shifted to predominance of secondary bile acids.

Again, those are the kind of bile acids that are generally associated with repression of 

 growth and proliferation. That was very consistent with the microbiome results we have seen. It was also very consistent with the clinical outcomes that we had seen, meaning we see a restoration of microbiome and bile acid, and concurrent with that, we see a real benefit to the patients in this trial, in terms of the primary end point being met.

This is a very exciting trial. This was the third trial in which we saw this positive benefit for patients. We’ve since run an additional 3 trials, 2 of which are pending readout. We’ve shared with the public the preliminary positive readout from our large phase 3 pivotal trial. This was the first of its type in the area, a large phase 3 randomized, placebo-controlled trial that was aimed at enabling an approvals process with the FDA. The significance of this trial within our developed program was that it’s building more and more evidence that we would eventually take to the FDA and argue for an approval of this investigational product.

For the industry and for the field at large, particularly for the patient population, it’s another demonstration that this type of standardized process and product has the potential to be a game-changer instead of just treating over and over with antibiotics. We’re aiming to have an approvable product that can restore the microbiome and get patients out of that vicious cycle of recurrence.

From a clinical perspective, we also saw that not only in the first 8 weeks did we see a benefit for reducing recurrence in this trial, but if you carried that out to 24 months—it wasn’t a primary end point of our trial, but it was something that we monitored prospectively—24 months after receiving treatment, the primary responders generally remained recurrence free. What we’re seeing is a durable long-term reduction of 

recurrence. That’s very exciting, and the clinical significance for the field is tremendous if we can get approvable products like this in their hands.

As for how we would anticipate this being administered in the clinic, I think that’s relatively straightforward. We anticipate it being administered per whatever label we would be granted. We won’t discuss the labeling today, but that’s what we would aim for, and that would be highly consistent with what we’ve tested in the trials, which is about reducing the recurrence at 8 weeks after treatment among patients who have already received standard-of-care antibiotic therapy.

RBX2660 for Recurrent Clostridioides Difficile

 We live in a society where it’s recognized that antimicrobial resistance is increasing. It’s proliferating, it’s being spread. Any options like a microbiota restoration treatment that would allow us to get away from more and more antibiotic usage does have the potential to reduce the spread of antimicrobial resistance.

We also know that in this patient population that is afflicted with 

], they’ve had an awful lot of antibiotics. Whatever they had originally that required them to have the antibiotic that stimulated the first 

, in addition to the treatments with antibiotics they had for the 

, this breeds antimicrobial resistant bugs, therefore, many of these patients are colonized in their gut with bacteria that carry resistance to various antibiotics. We were interested in looking at that in all our trials.

The trial that we talked about at ID [Infectious Diseases] Week 2020 was a different investigational product. It’s called RBX7455. In addition to RBX2660, this was a formulation we developed to be orally administered.

It’s a very interesting capsule in that it has some characteristics that are amenable to the patient. The number 1 being that it’s not frozen. It doesn’t have to be stored in the freezer. What that means is that participants or patients could come to the clinic, receive their first treatment, take it home, and self-administer outside of a health care setting. That’s exciting to us, and we were excited in this trial to test that. We’ve published the clinical findings from this trial.

This was a trial that was investigator-sponsored. It was a phase 1 trial conducted by Sahil Khanna, [MBBS, MS] at the Mayo Clinic in Rochester, Minnesota. It was an open-label trial designed to test 3 different dose ranges of RBX7455 in patients with recurrent 

All 3 doses had equivalent efficacy, an average of 90% recurrence free at 8 weeks after the last received treatment. That was also highly consistent with our other trials in which we saw a benefit for reducing CDI [

 infection] recurrence. The lowest dose in that trial that we administered was 2 capsules twice a day for 2 days. To me, that sounds much more like a standard drug. The patient experience is aimed at being something very manageable. The second day of those doses, as I mentioned, could be administered by the patient, self-administered outside a health care setting. We’re really excited about that possibility because it takes us to many indications beyond 

Given the clinical outcome of that trial, we had also looked at and published a very recent publication, in press right now in 

. We saw a similar microbiome response to the trials I talked about earlier. Specifically, we saw that patients who came to the trial, baseline is what I like to call them, before they received the treatment, they had a very disrupted microbiome. They had a lack of the good commensals and an overgrowth of bacteria that you wouldn’t want to see in a healthy microbiome. After treatment, that had shifted to become something much closer to a normal healthy microbiome that you would associate with resisting colonization by 

In light of that, we also wanted to look at that data. We look at the microbiome compositions by taking fecal samples from the patient and sequencing them so that we can read the sequence of all the bacteria in their gut. That tells us which bacteria are present. What we can also do is we can dig into those sequence and say among those bacteria present, what types of genes do they carry that would give them resistance to specific antibiotics?

Scientists can go into those genomes and find that there’s a gene that gives it resistance to a high-powered antibiotic, something called an 

, or extended spectrum beta-lactamase. That’s the type of bacteria that you hear about on CNN or in 

 that are pan-resistance problems. We found that before treatment, patients had a lot of these types of genes that confer resistance to antibiotics. After treatment, that had decreased to where participants had far fewer of these genes, and they were more similar in the total amount of genes they carried compared to a healthy population.

We also found that in a few of these patients you could find specific genes, one of those being the 

 gene. We found one of those in a patient prior to treatment with RBX7455, and it was not there after treatment. This is consistent with data that we’ve generated for RBX2660 in our other trials where you really see that there’s a potential for decolonization, of allowing those to be bred out from the microbiome from before to after treatment. That’s very exciting to us because not only are these patients no longer harboring or having resident in their gut a really dangerous pathogen, but it also presents the idea that we can go in to other populations beyond 

 where these types of bacteria could crop up at any time and cause a serious problem. We might be able to go into those patients and decolonize them as our specific aim of a treatment, and we’re exploring that in other trials right now.

Antibiotic Microbial Resistance & RBX7455 for C Diff

 There’s a lot of exciting work going on. The 

] field is very active right now. One of the things that we’re all waiting and watching for is another antibiotic in phase 3 clinical development called ridinilazole. It had a positive phase 2 trial. We’re all eager to see the phase 3 data.

More importantly, among Rebiotix Inc and parent company Ferring Pharmaceuticals and all the other companies running trials in this space, we’ve seen a real explosion of the knowledge around 

 as a pathogen, its pathogenesis, the disease, and how it affects patients. Our knowledge has increased exponentially over the last several years, and that’s really good for the patient, the health care system, and drug developers. We’re all learning more about how to manage this disease and how to improve it.

When we looked at that microbiome data for all of our trials, we were able to find a very clear pattern, which we call a Microbiome Health Index [MHI]. This is a single number based on the compositions of various bacteria, and we use it as a biomarker in our trials. What you see is that patients who come into the trial have been antibiotic treated, so they’re a good example of an antibiotic-induced dysbiosis, or antibiotic damage to the microbiome.

They have a very low MHI. After treatment, their MHI goes up much higher. Then we can actually derive a cutoff where we say, “OK, above this certain MHI level—the same way you would for other markers like blood pressure—is really indicative of a healthier microbiome. But if you get below that, you’re really starting to show some signs of antibiotic destruction or damage to your microbiome, which may trigger other considerations.”

 and ask the question for other populations, can you start to gauge what level of damage a certain antibiotic did to the microbiome? We’re starting to apply the MHI to those types of questions, and we’re seeing that the MHI is quite effective at telling a difference between what are thought to be microbiome-sparing versus microbiome-damaging antibiotics. That’s a small example of how this explosion in all the translational biology and clinical research around 

 has developed knowledge that extends beyond 

 and pushes this forward as a community, both for the patients and the health care providers, as well as the drug developers.

We’re seeing a lot of trials approaching the late stage. For our phase 3, we notified the public that we do have a preliminary positive phase 3 readout. We’re expecting to see positive data next year that we will roll out at a major conference. We will also be starting a large trial with the capsule formulation that I just mentioned. There’s a lot of excitement. When we talk about that phase 3 for RBX2660, that’s pivotal because it represents potentially the first approval in this microbiota-based live biotherapeutic class. That opens the doors for a lot of additional approvals, a lot of additional investments, and potentially transformational approaches to health care.

Clostridioides Difficile: Exciting Developments

] infection is important because it occurs frequently. It’s estimated that approximately 25% of all individuals who receive either metronidazole or vancomycin will recur. And of those who recur, 40% will go on to recur after that, and 50% to 60% will go on to recur again, and patients get caught in this cycle of recurrence. It is debilitating for the patients and also challenging for providers to handle.

In 2017, Gene K. Ma [MD], et al published a manuscript looking at the OptumRx database at the years from 2001 to 2012. They looked at the incidence of 

 during that timeframe, and it turns out that the incidence increased 42.7%. However, the incidence of multiply recurrent 

, that increased 188.8%, a truly remarkable change, speaking to the increased prevalence in our society, but more importantly, the refractory nature of this infection and the challenges that come with treating it.

In 2020, an epidemiologic study published in 

 looked at the Emerging Infections Program through the Centers for Disease Control and Prevention. Within that program they look at 10 counties throughout the United States and then projected data from those 10 counties on a national scale. Overall, in 2017 they estimated that there were 365,200 individuals who were diagnosed with 

, a major burden. In fact, they differentiated community-associated 

 from health care-associated infection. Health care-associated infection was defined as the onset of symptoms greater than 72 hours after admission to the hospital, or within 90 days of discharge.

It turns out that in 2017 the distribution of community and health care-associated infection was about 50/50. That’s important because health care-associated infection used to account for about two-thirds of the infections, and health care-associated infection is associated with increased rates of recurrence. In 2017, recurrence rates in community-associated infection were estimated to be 12.8% versus 15.3% with health care-associated infection, a trend for higher rates of recurrence.

 infection on our patients isn’t limited to the gut. This is an all-encompassing infection that also has an impact on patient’s lives and on them psychologically. This is something that I’ve seen through many years of treating and caring for these patients, and something that I know each of you who’s listening to this also has seen, even if it’s not in your conscious element.

 impacts our patients on multiple levels, and as a result, my study group did a retrospective survey of patients with either active 

 infection, asking them about their experience with the infection at present. We asked them about a number of elements, including their symptoms, whether they had abdominal pain, diarrhea, whether they were having fevers and sweats; the psychological element, whether they had stress, anxiety; the adaptational element, whether they were still wearing diapers or they had to change their eating habits; relational elements, including fear of incontinence. When they go to a public place, do they locate the bathroom and make a beeline so that they have a plan in the event that they had fecal urgency? And finally, productivity; do patients feel like they’re productive both in their home life and their professional life? And overall, across the board, patients both with active 

 infection and with a history, sometimes distant, several years in the past, more than 50% reported that they had a symptom effect still, as well as psychological, adaptational, and relational.

There were trends for higher amounts with the active infection, but greater than 50% even in the past reported that they still had these effects. From a productivity standpoint, the patients who had active 

 reported greater than 50% having this affect their work and their home life productivity. And greater than 30% reported, even with a distant history of 

, that this was still affecting their productivity.

It’s important for us to approach patients with this infection, to treat the infection and minimize the active symptoms, but also treat the entire patient. Listen to our patients, hear what they’re saying. There is a post-traumatic stress disorder that comes with 

 that we need to acknowledge and allow the patients to express themselves about, and boost their confidence. Explain to them that we’re going to do our best to minimize the rates of 

 and rates of recurrence from coming back. That will alleviate their fears, treat their anxiety, and treat the patient as a whole. Our goal is to treat the patient as a whole, not just their infection. And we can do that by acknowledging some of the other elements that come with this infection.

Frequency of CDI Recurrence and Impact on Quality of Life

 When it comes to risk factors for recurrence, it’s important for clinicians to understand what they are, to identify which patients are at greatest risk. But the ultrastructure for the risk factors for recurrence emanates from the risk factors for initial infection.

Let’s first focus on the risk factors for initial infection. I put these in 3 categories. The first category is demographics: age over 65, female gender; any form of immune compromise, chronic kidney disease, HIV, inflammatory bowel disease, inflammatory bowel disease on a biological agent, rheumatologic disease; medications, including antimicrobials and acid-suppressive therapies, such as proton pump inhibitors [PPIs] and histamine blockers.

Why do antimicrobials leave patients at risk for initial, and of course recurrent, 

? The best study that looked into this was published in 2008. It’s an older study but gives us a lot of information and was a foundational study. Within that analysis, they looked at 3 individuals who were controls: over 65 years of age, no 

 infection, no oncologic diagnosis. They compared them with 4 individuals who had an initial episode of 

. They compared the microbiota between no infection and initial infection, and initial infection and recurrent infection. And what they found was that when they compared no infection with initial infection, there were no statistically significant differences in terms of the diversity of the microbiota, how variable it was, or the constituency, what was actually there. When they compared initial infection with recurrent infection, there were statistically significant differences, with a depletion of the diversity, less variability, and a depletion of the 

, are the 2 most important phyla preventing proliferation of 

We learned 2 things from that study; one was that with initial 

 infection, patients have a bent microbiota but not a broken microbiota. When we treat this infection with antimicrobials, we’re targeting the bacteria with that initial treatment, but the microbiota most likely can regenerate itself. Once patients end up with recurrent 

 the microbiota is broken and the bacteria are proliferating, so we need to focus and target both to allow the patient to get better. Otherwise, it’s a mere coin flip of whether or not they’ll recur.

What about PPIs, acid-suppressive therapy? The astute listener will remember back to their text book years that 

 has a vegetative phase and a spore phase. The vegetative phase is the phase that releases the toxins that cause the diarrheal syndrome most commonly associated with this. The vegetative phase is susceptible to gastric acid. When it comes in contact with gastric acid, it gets wiped out. However, if the gastric acid is reduced with something like a proton pump inhibitor, then it’s more likely that the vegetative phase will access the small bowel and the large bowel, and more likely for people to get infections. And that’s what most of us thought for a long time, until 2015, when a small, but important manuscript was published.

At that time, researchers at Columbia University looked at a group of 21-year-old healthy individuals with no medical diagnoses, and taking no medications. They characterized their microbiota at time zero, and then 8 weeks later, after they gave them omeprazole 40 mg twice daily. What did they find: increases in enterococci and streptococci and decreases in clostridioides. Plainly stated, colonization resistance was weakened. What we’re realizing is colonization resistance in the microbiota plays a major role in prevention of 

, and when it’s altered, that’s a major mechanism for 

The third category of risk factors for initial 

 infection include environment; do individuals live in a skilled nursing facility, do they spend significant amounts of time in the hospital? As we understand the framework of risk factors for initial 

, we can now delve deeper into the risk factors for recurrence, which are basically the same. They include demographically, age over 65; any form of immune compromise; medications, including proton pump inhibitors, histamine blockers, antimicrobials agents, as well as chemotherapeutic agents. The hypervirulent strains are a risk factor for recurrence, the environment that patients live in, including skilled nursing facilities and spending significant amount of time in the hospital.

Many individuals ask what are the most important risk factors for recurrence. That was best delineated in a meta-analysis published in 2015. They looked at 33 studies and found that the 4 most important risk factors for recurrence were: age over 65, concomitant antimicrobials for another indication, proton pump inhibitors, and chronic kidney disease. As clinicians, those 4 risk factors are probably the most important for us to think about when we approach patients with 

 and consider our treatment options, and target decreased rates of recurrence to optimize patient outcomes.

Risk Factors for Recurrence of Clostridioides Difficile

 In February of 2018, the Infectious Diseases Society of America and the Society for Healthcare Epidemiology of America updated their joint guidelines for the first time since 2010, and that update came with a lot of change. Within those guidelines, they recommended treatment for initial infection be based upon severity of infection, specifically, nonsevere infection being defined as a white cell count less than 15,000 and creatinine less than 1.5 mg/dL. If patients met those criteria, then they had nonsevere infection, and it was recommended that they receive either vancomycin, 125 mg 4 times daily for 10 days, or fidaxomicin, 200 mg twice daily for 10 days. Notice that metronidazole was not a recommended therapy. The only time metronidazole was recommended in that initial nonsevere cohort was with patients who did not have access to either vancomycin or fidaxomicin. And for initial severe infection, metronidazole was completely off the table. For initial severe infection, defined by a white cell count greater than 15,000 or creatinine greater than 1.5 mg/dL, patients were only recommended to receive 10-day therapies with either vancomycin or fidaxomicin. For initial fulminant infection, defined by hypotension, shock, ileus and megacolon, we basically throw the book at the patients. We give intravenous metronidazole; we give oral vancomycin. If patients have an ileus, we give per rectum vancomycin, a little bit of prayer, and the patients usually do very well with that therapy.

For first recurrence, the guidelines significantly changed from 2010, where it was recommended that we reuse what was used initially. With these guidelines, for first recurrence, if patients received metronidazole originally, it was recommended that they receive vancomycin, 125 mg 4 times daily for 10 days. If they received vancomycin originally and recurred, it was recommended that they receive fidaxomicin, 200 twice daily for 10 days. And for patients in the middle, or patients who don’t fit those criteria, the clinical practitioner is recommended to use a prolonged vancomycin taper that is usually greater than 6 weeks, with a pulse at the end of that taper.

For 2 or more recurrences, the guidelines went with several different options; one, being a prolonged vancomycin taper greater than 6 weeks, if that hasn’t been given already, or a standard 10-day vancomycin treatment course of 125 mg orally 4 times daily, followed by rifaximin, 3 times daily for 20 days, a so-called rifaximin chaser. And finally, if patients hadn’t received fidaxomicin as yet, they recommended fidaxomicin, 200 mg twice daily for 10 days. But the greatest addition to those guidelines was the comment in 2 or more recurrences, where they recommended fecal microbiota transplantation. They recommended this after 3 completed antimicrobials courses in patients at greatest risk for recurrence. So we can see significant, tangible changes between 2010 and 2018 to these guideline-based treatments.

Treatment Recommendations from IDSA/SHEA for CDI

: At ID [Infectious Diseases] Week in October of 2020, we had a major update to the IDSA/SHEA [Infectious Diseases Society of America/Society for Healthcare Epidemiology of America] guidelines. This update took a provisional format that’s still being reviewed, but was being presented publicly as a precursor to a publication that should come in late 2020 or early 2021. These recommendations built upon the IDSA/SHEA guidelines from 2018. They initially took on the question of initial treatment of 

 infection or primary infection. And when they did a PICO [patient/population, intervention, comparison, outcomes] analysis with updated data, they decided that fidaxomicin, 200 mg twice daily for 10 days, should be used preferentially in front of vancomycin, 125 mg 4 times daily.

How did we get to that recommendation? Let’s look back at some of the literature that built on fidaxomicin. And what is fidaxomicin? Fidaxomicin is a narrow spectrum antimicrobial, meaning it targets 

 and has a minimal effect on the surrounding colonization resistance, or the surrounding microbiota. By doing that, you treat the 

 but you also minimize the collateral damage to the colonization resistance, minimizing risks of recurrence in the future. That’s theoretical, but that has been borne out in several studies, and let’s talk about them.

There were 2 phase 3 prospective randomized controlled trials published in 2011 that compared vancomycin with fidaxomicin head-to-head. Across those trials, 542 patients received fidaxomicin, 200 mg twice daily for 10 days, and 563 patients received vancomycin, 125 mg 4 times daily for 10 days, and then they were followed for 28 days thereafter for recurrence. They initially looked at initial treatment response. And initial treatment response was powered for noninferiority, and fidaxomicin achieved that, with a response rate of 88.2% versus 85.8% with the vancomycin. But what I described before is that fidaxomicin has that narrow spectrum, so it should have decreased rates of recurrence. And in the modified intention to treat analysis, that was achieved with statistical significance. Recurrence rates with vancomycin were 25.3%, whereas recurrence rates with fidaxomicin were 15.4%, a statistically significant difference favoring fidaxomicin.

Many of us practice in the real world and not as part of a prospective randomized controlled trial. The question of how well fidaxomicin performs in the real world came up in a study that was put forward by Simon Goldenberg, MD, et al. This is a study that was based out of the United Kingdom, looking at several medical facilities and health care systems that used fidaxomicin in a variety of ways.

Let’s first focus on using it for initial treatment. They used historical controls for their recurrence rates, and then prospective data for usage of fidaxomicin for initial infection, and in the 2 health care systems that I’m going to quote right now, for all infections. The historical data in health care system A within that study had a recurrence rate of 10.6%. Once fidaxomicin was added, 3.1%, a statistically significant difference. In health care system B, which also used fidaxomicin universally, the historical recurrence rate was 16.3%, versus 3.1% once fidaxomicin was being used. We can see a real significant delta and improvement, or lessening, of recurrence rates when fidaxomicin is being used.

 infection. And with this 2020 ID Week update to the IDSA/SHEA guidelines, they recommended using fidaxomicin in front of vancomycin for recurrence as well. Where did that come from? Let’s go back to the study that we were just discussing by Goldenberg, et al. In a group that received fidaxomicin for first recurrence, the historical controls had recurrence rates of 21.1%, versus 12.5% in the prospective group that received fidaxomicin. What we see is, even if fidaxomicin wasn’t used initially but was used for recurrence, recurrence rates decreased.

Now, that’s the real-world application, but there are also prospective randomized controlled data that looked into this, and that was a subgroup analysis of 28% of all the individuals in the pivotal phase 3 trials comparing vancomycin with fidaxomicin. In that group, 28% of the individuals had had 

 within the prior 3 months. When they looked at the rates of recurrence of the group that then received vancomycin, recurrence rates were 35.5%; the group that received fidaxomicin, 19.7%, a statistically significant reduction in rates of recurrence.

In addition, there’s a more modern study that was published a couple of years ago out of Europe. They looked at 364 individuals hospitalized with 

 infection and randomized them to either receive vancomycin, 125 mg 4 times daily for 10 days, or a unique application of fidaxomicin, giving it twice daily for 5 days, and then every other day for days 7 through 25, almost a taper of sorts. Overall, initial treatment response in the vancomycin arm was 82.1% versus 80% with fidaxomicin. Noninferior, so they were similar; however, rates of recurrence in the fidaxomicin arm were remarkably lower. Rates of recurrence with vancomycin were 19% versus 6.2% in the fidaxomicin arm, a statistically significant difference. Within this update to the 2018 guidelines, it is now recommended that fidaxomicin be used in front of vancomycin for first recurrence, with consideration either for 1 tablet twice daily for 10 days, or 1 tablet twice daily for 5 days, and then every other day for days 7 through 25.

Expanded Role of Fidaxomicin in Treatment of CDI

 There was one other significant update to the IDSA/SHEA [Infectious Diseases Society of America/Society for Healthcare Epidemiology of America] guidelines that was put forward at ID [Infectious Diseases] Week in 2020. That was a recommendation stating that bezlotoxumab should be considered in any individual with at least 1 risk factor for recurrence of 

] infection. Why is that? What are the data behind this?

The data behind this comes from 2 prospective, randomized controlled trials entitled MODIFY I and MODIFY II. These were published a couple of years ago. In these trials, 386 people were randomized to receive bezlotoxumab in MODIFY I, and 395 patients to receive bezlotoxumab in MODIFY II.

What is bezlotoxumab? Bezlotoxumab is a fully humanized monoclonal antibody designed to bind toxin B in a specific manner. By binding toxin B it theoretically decreases rates of recurrence, and it does that in prospective randomized controlled trials. Within the original MODIFY I and MODIFY II trials, there were other groups. If you’ve read the literature or you’re aware of the literature, one of those groups was actoxumab, a fully humanized monoclonal antibody to toxin A, and a combination of bezlotoxumab and actoxumab. Actoxumab wasn’t as efficacious as was expected, so this product didn’t come to market. And we’re going to limit our discussion on that today and focus solely on the placebo arms and the bezlotoxumab arms.

Within those prospective randomized control trials, the groups that received placebo in MODIFY I had a recurrence rate of 27% versus 16% in the group that received bezlotoxumab. In MODIFY II, recurrence rates with the placebo arm were 25%, and with bezlotoxumab, 15%. It’s essential to understand that bezlotoxumab is a one-time infusion given in addition to a standard of care antimicrobial, and that’s how it was administered within these studies.

Now, within these studies they also looked at risk factors for recurrence: age over 65, any history of 

 infection, any immune compromised state for the patients, the hypervirulent strain, NAP1/B1/027 strain, or severe infection. Overall, there were trends for decreased rates of recurrence across the board; however, in the age over 65 group, both studies achieved statistical significance in the subgroup analysis, with the number needed to treat to reduce recurrence in 1 patient, of 6. That’s truly remarkable. That became the foundation for these recommendations that I just put forward of using bezlotoxumab.

Where did they come up with that 1 risk factor for recurrence? They did a subgroup analysis, published by Dale Girding, MD, et al, that looked at these original phase 3 prospective randomized controlled trials and put them together. When they looked at patients who had 1 risk factor for recurrence from the list that I just put forward, the group that received placebo recurred 31.3%, the group that received bezlotoxumab, 17.1%. When patients had 2 risk factors for recurrence, recurrence rates in placebo were 41.1% versus 26.9%. Three or more risk factors for recurrence, 46.1% with placebo, versus 21.2% with bezlotoxumab. The more risk factors you have, the more effective the bezlotoxumab is. But we see that even with 1 risk factor for recurrence, bezlotoxumab nearly cuts in half the recurrence rates.

At ID Week in October of 2020, a nice abstract was put forward looking at the real-world practical usage of bezlotoxumab. Within this analysis, they looked at 120 individuals. They compared a group of individuals who received either standard of care antimicrobials alone between January of 2015 and December of 2017, or standard of care antimicrobials plus bezlotoxumab, the fully humanized monoclonal antibody one-time infusion, given in addition to that standard of care antimicrobial. That group was assessed from September of 2017 to September of 2019. Overall, 47 individuals received standard of care antimicrobial plus bezlotoxumab, and 73 individuals received standard of care antimicrobial alone. They then looked at the 90-day recurrence rates, and overall, bezlotoxumab made a significant difference. The group that received bezlotoxumab recurred 12.8% of the time, versus 42.5% in the group that received standard of care antimicrobials alone. A statistically significant difference, but a practical real-world data support for the IDSA/SHEA guideline update for individuals who have 

 infection that have 1 risk factor for recurrence, which was the group that was studied in this analysis, showing a remarkable difference from 12.8% to 42.5% for rates of 90-day recurrence. Following this provisional update to the IDSA/SHEA guideline, we should strongly consider using bezlotoxumab in a cohort of patients who have 

IDSA/SHEA Guidelines Update and ID Week: Bezlotoxumab

: The question of refractory versus recurrent 

 is typically defined by patients who have classic 

 diagnosed with stool assay, treated, and will recur in a fixed period with similar symptoms to when they presented originally. The issue arises with the timing for recurrence; some studies use 4 weeks, some studies use 8 weeks, some studies use 12 weeks, other studies use 24 weeks. The Centers for Disease Control and Prevention have landed on an 8-week follow-up, and most prospective randomized controlled trials use that 8-week marker.

Recurrent disease is fairly codified; however, refractory disease is not. Refractory disease is any patient who doesn’t seem to be responding to therapy but might not necessarily have that classic feeling better on antimicrobials and standard of care therapy, and then getting the symptoms again in the future.

A nice abstract was put forward at ID [Infectious Diseases] Week in October of 2020. Within that abstract they looked at the University of Virginia Health System for individuals who received fecal microbiota transplant for either recurrent infection or refractory infection. Within that abstract, they didn’t give clear definitions for recurrent and refractory infection, but what they put forward was that in the recurrent group, 5 out of 6 patients responded to a fecal transplant. Overall efficacy was 83%, whereas in the refractory group, 4 out of 7 patients responded, tabulating to about 57%.

What do we derive from this? What they derived from this is in a recurrent group of inpatients with 

 fecal transplants seem to work, and those numbers are on par with other studies. In the refractory group, they said you can give a fecal transplant, and it might work about 57% of the time. One of the most important pearls of understanding patients with 

 is understanding that if a patient is not responding to vancomycin or fidaxomicin, they probably don’t have 

 infection. Some 99.5% of the time, patients should have some response, at least halving the frequently of their bowels, and their stools should become somewhat formed.

One of the reasons I’ve enjoyed treating patients with 

, beyond curing them, is that a lot of individuals come to my office saying, “I have refractory 

.” And I sit down in the office with them and I say, “Well, what have you been treated with so far?” And they’ll tell me, “Well, I’ve received vancomycin.” And I’ll say, “Well, how many bowel movements were you having a day with the 

 before the vancomycin?” And they say, “7 or 8.” And I’d say, “Well, once you received the vancomycin, how many bowel movements were you having?” And they’d say, “7 to 8.” And I’d say, “Well, you probably don’t have 

. It’s my responsibility to try to figure out what that is, what your diagnosis is, and how we can get you better.”

What can be a diagnosis that we see in patients with 

 in the past? Post-infection irritable bowel syndrome [IBS] is common. It’s estimated that about 25% of patients who get 

 will end up with post-infection IBS. How do we differentiate them? With a history similar to what I provided recently; we ask the patient about the frequency of their bowel habits. Typically, with a post-infection IBS, patients’ bowel habits will be about half or less of what they presented with initially with 

. You can ask the patients about the odor of their stool. Believe it or not, patients will say, “Oh no, it smells like 

 right now,” or, “No, it smells like my previous odor.” If it smells like 

. If it doesn’t, most likely not. And of course, the definition of irritable bowel syndrome; what is the definition of irritable bowel syndrome? An association of abdominal discomfort with bowel movements, either a relief or worsening of that discomfort.

As a gastroenterologist, I have the ability to also do a flexible sigmoidoscopy or a colonoscopy if the diagnoses is in question. Take some biopsies, we can look for a diagnosis like microscopic colitis. Of course, it’s also important to review the patient’s medication lists. A lot of these patients have multiple medical comorbidities. Perhaps they had a medication that was added recently that caused loose stools and softening of the stools, increased frequency. As a clinician, when it comes to recurrent 

, and when it comes to this “refractory 

,” unfortunately, we have to put on our thinking caps, go through a differential diagnosis and figure out what’s going on, to help those patients feel better.Sometimes it’s a simple recurrence, we can tease that out through history; sometimes it’s not, and we can tease that out through some of the tools we have available to us. But a clinical history is essential in differentiating those who have a true recurrence versus those who have a “refractory disease” that might be a result of another diagnosis.

Fecal Microbiota Transplant for Recurrent vs Refractory CDI

The question of which patients respond best to a fecal transplant who have a history of recurrent 

] is an important one, and there have been a number of case series that have looked into this. This question was tackled at a major infectious disease conference in October of 2020. They looked retrospectively at a cohort of patients who received a fecal transplant within their health care system. The fecal transplant material was supplied by a stool bank. They looked overall at 81 patients and found that 89% responded to the fecal transplant and had suppression of their 

 infection and clinical cure. Right on target with what all or most of the other retrospective studies that have looked at this have shown. But they also showed that 36% of individuals also had transient loose stools and persistent loose stools after the fecal transplant. Now, this is a known effect. Fecal transplants have been shown to be associated with several subtle or less subtle adverse events, one of them being persistent loose stools, or transient loose stools, another being gas and bloating, another being constipation, and finally, mild abdominal discomfort. These [adverse] effects usually last several months, maybe 3 or 4 of them.

 will get a post-infection IBS [irritable bowel syndrome]. Of the group that have more refractory symptoms, or more recurrences, they’re more likely to get post-infection IBS, and that is probably why there was a higher percentage seen here. Who is at greatest risk for getting a post-infection IBS? Patients who had IBS in the first place is what they showed here. Who are more likely to respond to the fecal transplant? Patients who received longer antimicrobial courses before the transplant, and patients with a higher body mass index. It’s unclear why patients with a higher body mass index will be more likely to respond to a fecal transplant, but it’s clear why patients who received more antimicrobials prior to the transplant are more likely to respond. They’re probably treated completely prior to the transplant, and the transplant is a reenforcing factor.

As we discussed previously, in patients who have recurrent 

, we want to treat both the bacteria, but also the microbiota. The antimicrobials, when patients have received prolonged antimicrobials courses, that has probably done the trick, and supplementing the colonization resistance with the microbiota gives it that knockout punch. The longer the antimicrobials, the more likely to get rid of the bacteria, reenforcing the colonization resistance with the fecal transplant.

When we approach patients with recurrent and multiply recurrent 

, thinking about the body mass index, thinking about the length of time that they’ve received vancomycin is essential to understanding who might respond, according to this study. But also understanding that patients might get transient or persistent loose stools afterward as a result of a post-infection IBS is also essential for all of us practitioners to consider when we use this treatment for our patients.

It is an exciting time in the world of therapeutics for 

 infection, and recurrent and multiply recurrent infection, but 2021 is framing up to be a pivotal year in the management of recurrent 

 infection. Why is that? That is because we have a number prospective randomized controlled trials of pharmaceutically produced fecal microbiota transplantation material that is possibly going to gain FDA approval in 2021.

The 3 products are from Rebiotix/Ferring [Pharmaceuticals], RBX2660, an enema formulation of fecal transplant, just completed a phase 3 prospective randomized controlled trial with positive topline results, showing a beneficial effect compared with placebo. SER-109 [from Seres Therapeutics, Inc], an oral capsule formulation of 

 spores, a form of fecal transplant that also had positive, topline phase 3 prospective randomized-controlled trial results. And finally, CP101, from Finch Therapeutics, they completed a phase 2 prospective randomized controlled trial, and hopefully will be launching a phase 3 trial in 2021 for data analysis perhaps in 2022. We can see that more codified and less heterogenous forms of fecal microbiota transplant with potentially FDA approval are coming in 2021. With less heterogeneity of these products, we have more stable efficacy and safety data, and as clinicians we should be excited for more predictability of usage of these materials and better outcomes for our patients, with more widespread availability of such products.

Paradigm Shift in the Management of Clostridium Difficile Infections