Thank you for the invitation. The title of the talk is Beyond Cytokines, Alternative Targets for Host-Based Blood Purification. These are my disclosures. I'm a site investigator at my university for the following trials, and for the three filters that I'll be discussing today. And so let's start. Why even consider extracorporeal blood therapy for sepsis? Well, there's increased incidence of drug-resistant pathogens. There's also paucity of novel antimicrobial therapies. And septic patients are being left with fewer antimicrobials to be treated with. And with continuous and direct access to the blood, these therapies may be used as adjuvants to treat a dysregulated immune system. So let's first discuss the steps of immune response to pathogen exposure before we discuss some of the filters involved in clinical trials in the United States. All pathogens express undersurface pathogen-associated molecular patterns, also known as PAMs. PAMs are recognized by the pattern recognition receptor on leukocytes, leading to activation of white blood cells, synthesis and release of cytokines, and massive release of cytokines may lead to organ dysfunction. Injured host cells, in turn, express undersurface damage-associated molecular patterns, which, in turn, interacts with the pattern recognition receptor, fueling more cytokine production, and fueling this vicious cycle of immuno-inflammatory response and organ dysfunction. There are different extracorporeal blood therapies, and these therapies target different steps of the immune response. Most of them target one step of the immune response, but actually some of them target more than one step. Some of them target the pathogen. Some of them target PAMs and endotoxins. Some target activated leukocytes and cause immunomodulation by changing the phenotype of neutrophils and monocytes, and some remove cytokines. And given the title of my talk, which primarily stressed that I will not be talking about cytokine removal, I will be focusing on these three filters or cartridges, which are also currently either being evaluated in a clinical trial or will be evaluated in a clinical trial in 2023. The first cartridge that I want to discuss is the Seraph cartridge. It's a hemoperfusion cartridge, which is a pathogen-binding cartridge, and it's marked for use in Europe, and it was granted FDA approval for use under emergency use authorization in patients with COVID-19. And in the United States, the Seraph cartridge is currently undergoing a clinical trial evaluation under an IDE with the FDA, and the trial is called the PURIFY-RCT trial. The Seraph filter may be used as either as a standalone configuration, or it may be used in conjunction with a dialyzer or a hemo filter, and it's compatible with most hemodialysis machines or CRRT machines in the market, as well as hemoperfusion machines. Now, how does it work? The Seraph filter mimics the function of the endothelial glycocalyx. The endothelial glycocalyx is a matrix that lines the vascular endothelium, and its constituents are glycoproteins, proteoglycans, and glycosaminoglycans. And the heparan sulfate proteoglycan binds pathogens, including fungi, bacteria, and viruses. And the Seraph filter is made up of microbeads with chemically bonded heparan sulfate, which binds pathogens. There are no clinical trials with Seraph filter as of yet, but there are many case series and observational studies. This is the most recent observational study utilizing Seraph filter in patients with severe COVID-19. And this was a retrospective study, and 53 patients treated with Seraph were matched by study site with 53 control patients. And the mortality in those patients treated with Seraph was lower than those in the control group, 32% versus 64%. And they also had more vasopressor-free days. And in a multivariate model adjusted for potential confounding effects, the beneficial effect of Seraph 100 or Seraph on the mortality persisted. And the Purify Our City study is a multi-center open-label randomized control trial evaluating Seraph in patients with pathogen-associated shock and the trial currently is enrolling in the United States. Moving on to the next filter, the polymyxin B cartridge. So the polymyxin B cartridge is an endotoxin binding cartridge. Its indications for use include sepsis and endotoxemia or suspected gram-negative infection. And outside the United States, it's been used on more than 300,000 patients for more than 30 years. And at the moment, the PMX cartridge is undergoing a clinical trial under an ID with the FDA named the TIGRIS trial. Now, the cartridge is basically a polystyrene-based fiber with polymyxin B covalently immobilized on the surface of the filter. And the strong covalent bond prevents PMX from detaching and entering the bloodstream and this is very important because that will prevent the patients from the neurotoxic and nephrotoxic effects of polymyxin. And how does it interact with the lipopolysaccharide or endotoxin molecule? It does so by strong hydrophobic interactions between the hydrophobic residues on polymyxin B and the hydrophobic residues on the lipid A portion of the lipopolysaccharide, as well as weaker ionic interactions between positively charged amino groups and the negatively charged phosphate groups on the lipopolysaccharide. And these weaker ionic interactions extend the threshold distance for capturing endotoxins. And here are the most recent clinical trials with PMX published outside of Japan where it's primarily used. The two trials, the UFAS and Abdomix trial were in patients with abdominal sepsis and these two trials showed conflicting results. The Euphrates trial was the latest published clinical trial with PMX and it included septic patients with an endotoxin activity assay of greater than 0.6. Patients randomized to PMX received two sessions of PMX for two hours, 24 hours apart. And the 28-day mortality between the two groups, the PMX and the control was similar, including those patients who had a multi-organ dysfunction of nine or greater. So there are multiple possible reasons as to why polymyxin hemoperfusion may have failed to improve survival in Euphrates trial. It may be that the beneficial effect of therapy is initiated after the onset of septic shock and MODS. It may also be that the whole blood assay that was used in this trial may insufficiently reflect the endotoxin burden. Or it could be that the dose and duration of polymyxin B hemoperfusion as applied in this trial may have been insufficient. And in vitro experiments published almost at the same time as the Euphrates trial showed that the relationship between endotoxin activity assay on the x-axis and the lipopolysaccharide concentration or endotoxin concentration is actually asymptotic. And in those patients who have endotoxin assay of 0.9 or higher their endotoxin concentration can be four nanograms per mL or many folds higher. So it could be eight, it could be 10, it could be 15. And if you think about it, the PMX matrix can bind about 20 micrograms of endotoxin. And if the blood endotoxin concentration happens to be greater than four nanograms per mL, then the endotoxin load in the whole blood of a five liter, let's say, will be greater than the binding capacity of PMX. And if you assume that actually endotoxin is not only distributed in blood but also in the interstitial fluid, then the endotoxin load in whole blood and the interstitial fluid will definitely exceed 20 micrograms. Again, this is among patients with very high endotoxin levels in the blood. And in a post hoc analysis of the Heifrey's trial, among patients who had endotoxin assay activity of 0.6 but less than 0.9, actually the survival of patients who received PMX was better. And it could be explained probably by the fact that those are the patients whose PMX could handle the endotoxin load. And the Tiger's trial is currently enrolling and it's a multi-center open-labeled randomized control trial. And we are one of the study sites. And the main inclusion criteria is patients having MODS greater than nine and endotoxin assay activity of greater than 0.6 but less than 0.9. I'm gonna now move on to the selective cytophoretic device. The SCD is a hollow fiber with blood flowing in the extra capillary space rather than in the hollow fibers. And due to the low shear force and in the presence of low ionized calcium which is required for its activity, the SCD sequesters the most activated neutrophils and monocytes taking them out of circulation. And this process results in immunomodulation of the circulating glucocytes. Now, the SCD cannot be used without CRRT because it requires low ionized calcium and citrate anticoagulation use. And in general, the SCD is changed every 24 hours and it could be used up to 10 days of treatment. And so, and unlike some of the other filters available in the market which primarily focus on cytokine removal, it diminishes the activity of neutrophils and monocytes and can decrease the production rather than the removal of cytokines. And the safety of the SCD has been demonstrated in seven clinical or human trials. And these trials also suggested a strong efficacy signal. But the largest randomized controlled, but the only randomized controlled trial was this trial and it was the largest. And unfortunately, and it published in 2015, the study was terminated early because of national shortages of calcium and inability of many centers to keep the circuit ionized calcium less than 0.4, which is required for SCD activity. But if you look at this slide, which is the protocol approach, and in those patients who achieved circuit ionized calcium less than 0.4, the 60-day mortality was actually lower, although statistically not significant, but the p-value was 0.07. But the 60-day dialysis dependence was lower in the SCD group and the composite outcome of both was much better in the SCD group. So essentially, the SCD requires the use of regional anticoagulation and for it to work. And there's no reason why we cannot achieve circuit ionized calcium less than 0.4 on all patients. This is a study by our group, not with the SCD, but with citrate anticoagulation that we showed that you can even achieve circuit ionized calcium less than 0.4 in patients with shock liver and no liver function. And this is against what the KDGO guidelines or the nephrology guidelines recommend. And this is the most recent trial with the SCD and the study was set to evaluate the safety and clinical outcomes with the SCD in COVID-19 patients with multi-organ failure. And the inclusion and exclusion criteria are seen here. And the main inclusion criteria was having COVID-19 positivity and at the same time have either AKI requiring CRRT or being ARDS on mechanical ventilation. And two centers were involved in this trial and the two centers were part of CRRT net, which is basically a prospective observational registry that provided contemporaneous set of controls for comparison with the patients who received the SCD. And the patients treated with the SCD, almost all of them were on corticosteroids and many of them received or were on remdesivir or were treated with remdesivir. And the patients were treated up to 10 days with the SCD. And a total of 22 patients were involved with AKI requiring CRRT or ARDS on mechanical ventilation. All patients but one had AKI and were all on CRRT and mechanical ventilation and nine patients were on ECMO. And you can see that the contemporaneous control group was similar in clinical characteristics and the acuity of the disease compared with the SCD treated group. There were no device related adverse events or significant adverse events, including in those with ECMO, no citrate related adverse events and more than 90% of the reported circuit ionized calcium were at target and the systemic ICAL remained normal. There was no incidence of leukopenia, neutropenia and thrombocytopenia. And 60 day mortality in the control group was 80%. And this was similar with the mortality reported in the literature in patients with COVID-19 with ARDS on mechanical ventilation and requiring dialysis. The mortality rate in the SCD group was 50%. And in those patients who actually were treated beyond 96 hours and whom a care was not withdrawn, it was 31%. Again, this is not a randomized control trial but it's the latest study with the SCD. So there are few planned multi-center trials with the SCD in 2023, including in patients with septic shock. And so with this, I will conclude that there is growing evidence for use of extracorporeal blood therapies for pathogen removal, endotoxin removal and perhaps even reprogramming certain host immune cells. But the exact timing for initiation, duration of use of these therapies is poorly understood. And all these therapies are currently under assessment in clinical trials but I think many questions will remain to be answered even after the clinical trials. Thank you.

host-based blood purification

extracorporeal blood therapy

cytokines release

Seraph cartridge

immunomodulation