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 microbeads 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 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 It is likely that by binding COVID-19 and resultant inflammatory mediators, Seraph 100 may improve patient outcomes.7 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

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. In the PURIFY observational trial, 3 of 4 analysis methodologies yielded improvements in survival: Odds ratio of 0.26 (95% Cl 0.09-0.79, p=0.016), 0.27 (95% Cl 0.10-0.73), and 0.31 (95% Cl 0.12-0.80) respectively: Nearly 4X improvement in survivability odds when severely ill COVID-19 patients are treated with Seraph 100.7 Interim results of the COSA registry for COVID-19 patients in Europe and Africa show significant survival improvement for Seraph 100 treatment(s) initiated <60 hrs (2.5 days) after ICU admission.10

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

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 SW, Oliver JD, Collen J, et al. Treatment for Severe Coronavirus Disease 2019 With the Seraph-100 Microbind Affinity Blood Filter. Crit Care Explor. 2020;2(8):e0180. Published 2020 Jul 30. doi:10.1097/CCE.0000000000000180
3. Seffer MT, Cottam D, Forni LG, Kielstein JT. Heparin 2.0: A New Approach to the Infection Crisis. Blood Purif. 2021;50:28-34. doi: 10.1159/000508647
4. Data on file, Exthera Medical Corporation
5. Fajnzylber J, Regan J, Coxen K, et al. SARS-CoV-2 Viral Load is Associated with Increased Disease Severity and Mortality. Nat Commun. 2020;11:5493. doi: 10.1038/s41467-020-19057-5
6. Bermejo-Martin JF, González-Rivera M, Almansa R, et al. Viral RNA Load in Plasma is Associated with Critical Illness and a Dysregulated Host Response in COVID-19. Crit Care. 2020;24(1):691. doi:10.1186/s13054-020-03398-0
7. Chitty SA, Mobbs S, Rifkin BS, et al. A Multicenter Evaluation of the Seraph 100 Microbind Affinity Blood Filter for the Treatment of Severe COVID-19: PURIFY OBS Publication Published in April. Crit Care Explor J. 2022;4(4):1-11. doi: 10.1097/CCE.0000000000000662
8. EU CE Mark approval: Ref 0459
10. Schmidt JJ, Borchina D, van’t Klooster M, et al. Interim Analysis of the COSA (COVID-19 Patients Treated with the Seraph 100 Microbind Affinity Filter) Registry. Nephrol Dial Transplant. 2022; 37(4):673-680. doi: 10.1093/ndt/gfab347

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