Eculizumab Is An Effective Long-Term Treatment In Patients with Atypical Hemolytic Uremic Syndrome (aHUS) Resistant to Plasma Exchange/Infusion (PE/PI): Results of An Extension Study

aHUS is a genetic, systemic disease with a devastating prognosis caused by chronic uncontrolled complement activation leading to thrombotic microangiopathy (TMA), progressive organ damage and premature mortality. In a 26-wk phase II trial, pts receiving ECU, a terminal complement inhibitor, had a highly significant increase in platelet count (a measure of TMA improvement) (primary endpoint: 73×10⁹/L increase; p=0.0001). 13/15 pts with low platelet count at baseline (BL) (ITT) had platelet normalization at Wk 26. 15/17 pts (88%) achieved TMA event-free status (≥12 wks of stable platelet count, no PE/PI and no new dialysis). 13/13 pts treated with ECU for 26 wks had platelet normalization at Wk 26 and 15/15 treated with ECU for 26 wks achieved TMA event-free status. Median TMA intervention rate was 0 (no. of PE/PI and new dialysis events/pt/day). Importantly, 4/5 pts on dialysis with PE/PI discontinued dialysis with ECU. ECU was well tolerated (Legendre. ASN 2010). We report longer follow-up data from the extension phase of this ongoing trial.

Pts ≥12 yrs with aHUS and persistent TMA despite ≥4 PE/PI sessions 1 wk before screening were enrolled in a 26-wk, controlled, open-label, single-arm phase II trial and continued into an extension trial. ECU dosage: 900mg/wk for 4 wks, 1200mg at Wk 5, 1200mg q2 wks. All pts received a meningococcal vaccine and prophylactic antibiotics ≥14 days after vaccination. Efficacy analyses were based on ITT population.

17 pts enrolled (2 discontinued at Wks 1 and 6; systemic lupus erythematosus [protocol violation] and an adverse event unrelated to ECU, respectively). Median time from diagnosis to screening=10mo (0.3–236). Median duration from overt clinical manifestations of aHUS to screening=0.75mo (0.2–4). Median number of PE/PI sessions per pt during aHUS current clinical presentation=17 (2–37). 5 patients (29%) required dialysis at baseline. Median age=28 yrs. 4 pts (24%) had no identified complement regulatory factor mutations (CRFM). ECU mean (SD) duration=58 (29) wks at data cut-off. Mean change (SD) in platelet count from BL was maintained (97×10⁹/L [81] at Wk 26 vs 98×10⁹/L [60] at 1 yr). All 13 pts who had platelet normalization at Wk 26 continued to maintain normal levels at data cut-off. The same 15/17 (88%) pts achieved TMA event-free status at data cut-off. All pts receiving sustained ECU treatment throughout the study achieved TMA event-free status at data cut-off. Renal function was maintained and continued to further improve in pts with ongoing ECU: improvement ≥1 CKD stage from BL: from 10 (59%) pts at Wk 26 to 11 (65%) pts at data cut-off and ≥25% decrease in creatinine from BL: from 11 (65%) pts at Wk 26 to 13 (77%) pts at data cut-off. With sustained ECU therapy, only 1 of the 5 pts at baseline continued on to require dialysis and no patient newly required dialysis (as of data cut off). Long-term chronic ECU was similarly effective in pts with/without identified CRFM. ECU was generally well tolerated; adverse events deemed related to ECU were reported in 12 pts (mostly mild to moderate, 1 severe). The extension trial continues.

In aHUS, despite PE/PI, >50% of pts either die, require dialysis, or have permanent renal damage within the first year of diagnosis. In contrast, all pts treated with ECU for a mean duration of >1 yr remain alive, 4 out of 5 pts became dialysis free, and no pt newly required dialysis. This demonstrates that continued ECU treatment significantly transformed the clinical course of aHUS in this pt population. In addition, long-term ECU therapy suppressed TMA and dramatically improved renal function. These long-term follow-up data further strengthen the evidence for ECU as the new standard of care for aHUS.

Greenbaum:Alexion: Consultancy, Honoraria, Research Funding, Speakers Bureau. Off Label Use: Eculizumab for the treatment of atypical hemolytic syndrome as part of clinical trials. Babu:Alexion: Research Funding. Furman:Alexion: Research Funding. Sheerin:Alexion: Research Funding. Cohen:Alexion: Research Funding. Gaber:Alexion: Research Funding. Delmas:Alexion: Research Funding. Loirat:Alexion: Research Funding. Bedrosian:Alexion: Employment. Legendre:Alexion: Research Funding.