Frequently Asked Questions

Learn More About Seraph 100 and ExThera Medical

What is the Seraph?

The Seraph® 100 Microbind® Affinity Blood Filter (Seraph 100) is a single-use broad-spectrum extracorporeal hemoperfusion device for use as an adjunctive treatment for COVID-19 infection.1 It is designed to treat bloodstream infections by binding pathogens from the blood, including SARS-CoV-2 (COVID-19).2,3 Learn more

What is the Seraph?

The Seraph® 100 Microbind® Affinity Blood Filter (Seraph 100) is a single-use broad-spectrum extracorporeal hemoperfusion device for use as an adjunctive treatment for COVID-19 infection.1 It is designed to treat bloodstream infections by binding pathogens from the blood, including SARS-CoV-2 (COVID-19).2,3 Learn more

How does the Seraph 100 work?

As blood flows through the Seraph filter, it passes over proprietary beads coated with molecular heparin receptor sites that mimic the heparan sulfate receptors on human cells that pathogens attack when invading the body. These harmful pathogens, which include bacteria, viruses, fungi, and other disease-causing molecules, bind to the Seraph beads and are removed from the bloodstream without negatively impacting the blood cells or proteins.3 

Are there any known side effects or potential dangers?

Possible Seraph 100 side effects include those seen in patients undergoing other extracorporeal treatments like dialysis. The Seraph 100 safety profile is consistent with standard extracorporeal labeling.

How is the Seraph different from other blood filters?

Some other blood filters remove inflammatory mediators, but do not address the source of the disease. Preclinical and clinical studies demonstrate that Seraph can efficiently remove pathogens while also reducing the concentration of inflammatory mediators and other substances that contribute to the severity of COVID-19.3 

How does blood filtering help treat COVID-19?

COVID-19 is not just a disease of the respiratory system. Peer-reviewed literature confirms that SARS-CoV-2 enters the bloodstream during moderate to severe COVID-19 infections.5,6,7 Viral RNA, the genetic material of the virus, can be found throughout the body in kidney cells, in heart cells, and in the blood vessels themselves that circulate the body through the bloodstream. Several publications have demonstrated a correlation between disease severity and the amount of virus that is in the blood.5,6,7 It is likely that by binding COVID-19 and resultant inflammatory mediators, Seraph 100 may improve patient outcomes. Seraph 100 is CE marked and commercially available in Europe and available in the US through Emergency Use Authorization (EUA) granted by the FDA for the treatment of COVID-19.8,9

“Cytokine storms” appear in severe COVID-19 cases. Can the Seraph help prevent these?

The cytokine storm is known to occur in some severe COVID-19 patients. However, publications have reported that cytokine levels are significantly lower in most severe COVID-19 patients with acute respiratory distress syndrome (ARDS) as compared to patients with septic shock, both with and without ARDS.5,10 Data has shown that SARS-CoV-2 viremia is associated with elevated cytokines.7 The Seraph 100 may help prevent the cytokine storm by binding the virus before the storm occurs. Additional data indicates that inflammatory mediators such as IL-6, ferritin, and D-dimer have dropped either during or shortly after treatment with Seraph 100.11

How do I use the Seraph 100 to treat COVID-19?

The device has standard luer fittings and a low pressure drop making it compatible with most blood pumps and dialysis equipment.4 Patients can be treated with the filter using flow rates between 100 and 350 mL/min.1 Patients should be systemically anticoagulated prior to treatment.1 Clinicians have observed the best results when patients are treated prior to or soon after needing intubation/mechanical ventilation, but doctors are also able to benefit some patients who have been intubated for extended periods of time. Refer to the product Instructions for Use (IFU) for greater detail.1 

When should I start treatment with the Seraph 100?

The Seraph 100 is usually reserved for the severe or critically ill patient per the following indications for use (IFU):1

Seraph 100 is reserved for patients with laboratory-confirmed and symptomatic COVID-19 with any of the following: 

      • Early acute lung injury (ALI)/early acute respiratory distress syndrome (ARDS)

      • Severe disease, defined as: 
        • Dyspnea 
        • Respiratory frequency ≥ 30 breaths/min 
        • Blood oxygen saturation ≤ 93%, 
        • Partial pressure of arterial oxygen to fraction of inspired oxygen ratio < 300, and/or 
        • Lung infiltrate >50% within 24 to 48 hours 
      • Life-threatening disease, defined as: 
        • Respiratory failure 
        • Septic shock, and/or 
        • Multiple organ dysfunction or failure 

Please consult the instructions for use in entirety for complete information of safety and appropriate use of the Seraph 100.

What evidence is there to demonstrate the effectiveness of Seraph 100?

In Europe, a human clinical trial determined the safety and performance of the device in use, necessary for CE mark.8 Clinical studies are underway in the United States and Europe check out our clinical trials page to see ongoing trials. Multivariate analysis of preliminary data from the PURIFY observational trial show nearly 4X odds ratio improvement in survivability for critically ill patients treated with Seraph 100 compared to contemporaneous controls.12  Interim results of the COSA registry for COVID-19 patients in Europe and Africa shows significant survival improvement for Seraph 100 treatment(s) initiated <60 hrs (2.5 days) after ICU admission.13

Are there registries/studies where I can participate in the EU?

Several clinical trials are underway and can be viewed on the Clinical Trials page.


  1. Seraph 100 Microbind Affinity Blood Filter Instructions For Use: CP021 Rev A FDA EUA200165
  2. Olson et al, Treatment for Severe Coronavirus Disease 2019 With the Seraph-100 Microbind Affinity Blood Filter, Critical Care Explorations, (2020), 2(8),1-6
  3. Seffer et al, Heparin 2.0: A New Approach to the Infection Crisis, Bld Purification (2020); Jul 2, 1-7
  4. Data on file, Exthera Medical Corporation
  5. Fajnzylber et al, SARS-CoV-2 viral load is associated with increased disease severity and mortality, Nature Communications; 2020, (11);5493
  6. Bermejo-Martin et al, SARS-CoV-2 RNA viremia is associated with a sepsis-like host response and critical illness in COVID-19; Crit Care, 2020, 24;691
  7. Chen et al, Detectable 2019-nCoV viral RNA in blood is a strong indicator for the further clinical severity, Em Mic and Inf; 2020, 9;469-473
  8. EU CE Mark approval: Ref 0459
  10. Kox et al, Cytokine Levels in Critically Ill Patients With COVID-19 and Other Conditions. JAMA. 2020;324(15):1565–1567
  11. Sandoval et al, Treatment for Severe Coronavirus Disease 2019 with a biomimetic sorbent hemoperfusion device in patients on hemodialysis, Clinical Kidney Journal, 2021; sfab010
  12. Chitty et al, A Multicenter Evaluation of Blood Purification with Seraph 100 Microbind Affinity Blood Filter for the Treatment of Severe COVID-19: A Preliminary Report, (2021).
  13. Schmidt et al, Interim-analysis of the COSA (COVID-19 patients treated with the Seraph ® 100 Microbind ® Affinity filter) registry, NDT, (2021).