Use of the Seraph 100 Microbind Affinity Blood Filter in a Pediatric Patient with Persistent BK Nephropathy

Introduction: BK nephropathy (BKN), a cause of kidney failure in solid organ transplant recipients, has no approved treatment strategy. Most providers trial immunoreduction which risks rejection of the transplanted organ. The Seraph® 100 Microbind® Affinity Blood Filter (Seraph® 100) (ExThera Medical Corporation) mimics the action of the natural glycocalyx to bind pathogens via heparin sulfate proteoglycans in patients on Continuous Renal Replacement Therapy (CRRT). It has been used to treat COVID-19, Adenovirus, Epstein-Barr Virus, and Cytomegalovirus with variable efficacy. Based on aforementioned viral load reduction with the Seraph® 100, we hypothesize this filter will reduce BK viral load in our patient. Case Description: A 14 yo female with dilated cardiomyopathy presented 8 years following cardiac transplant with new onset BK viremia (BKV). Her BK PCR titers peaked at 9,600,000 IU/ml. She was treated with Leflunomide, IVIG and immunoreduction. Despite reduction in BK titers, her glomerular filtration rate progressively declined. Persistent BKV was considered a contraindication to kidney transplant for which she would have otherwise qualified. With her impending need for dialysis, CRRT was initiated using the Seraph® 100 for 48 hours with a filter change at 24 hours. No adverse effects were noted. The patient was discharged to continue outpatient hemodialysis. Figure 1 shows trends of BK levels from time of initiation of Seraph® 100. Two months post Seraph® 100, BK level was undetectable without any new interventions. She underwent kidney transplant and is 3 months post-transplant without recurrent BKV. Surveillance biopsy at 3 months demonstrates no evidence of BKN. Discussion: We demonstrate the clearance of BKV in a heart transplant patient with BKN related end stage kidney disease, 2 months post utilizing the Seraph® 100 filter, allowing for successful kidney transplant. Ongoing studies are needed to confirm and evaluate continued success of the Seraph® 100 in patients with BKV.