Background and importance Complement mediated thrombotic microangiopathy (C-TMA) is caused by complement disruption that leads to haemolysis and thrombocytopenia. Eculizumab inhibits C5b-9 complex formation by binding protein C5 and has been approved for C-TMA. Nevertheless, studies on the effectiveness of eculizumab under real world conditions are scarce, even considering its high cost.

Aim and objectives To evaluate the efficacy and cost of eculizumab in clinical practice for C-TMA after 26 weeks (W) of treatment.

Material and methods Patients diagnosed with C-TMA whose treatment with eculizumab had been approved (900 mg/W for four doses and 1200 mg/W thereafter) and ongoing for >26W were included. Clinical variables were obtained from the electronic health records. Laboratory tests were evaluated at baseline, and at 12W, 26W and 38W after initiation of treatment. C-TMA remission was defined as lactate dehydrogenase (LDH) less than the upper limit of normal (ULN), platelet count >150×10E9/L and <25% creatinine increase from baseline.

Results Six patients were included (1 woman) with a median age of 43 years (range 23–59); none had genetics related to complement alteration. One patient had a pulmonary transplant and one a renal transplant. Median duration of treatment was 10 (6.8–45.5) months. Two patients stopped treatment because of resolution of C-TMA. Estimated cost of eculizumab treatment for 26W was 337 300€. Median cost estimated per treatment was 160 458€ (118 055–640 870).

Haemoglobin increased from 11 (8.2–12.7) g/dL at baseline to 12 (10.2–13.20) g/dL after 26W and to 13 (9.8–13.1) g/dL at 38W. Reticulocytes decreased from 112 (90.8–190.3) to 65 (44.1–85.4) after 26W (normal values 50–100×10E9/L) (p=0.18).

Platelets increased from 206 (44–359)×10E3 platelets/µL at 0W to 291 (175–305) at 38W. All patients recovered >150×10E3 platelets/µL within 26W.

LDH decreased in all patients: 511 (323–1787) U/L at 0W, 487 (288–1351) U/L at 12W, 491 (313–642) U/L at W26 and 430 (266–642) U/L at W38; 3 patients had LDL >ULN after 38W.

Median creatinine decreased (not significant). Renal function was maintained or improved in 4/6 patients. Two patients were in dialysis and one stopped. CH50 decreased in all patients and was undetectable for most patients within 12W (p=0.001). There was no significant change in C3 and C4. Two patients were in remission after 26W.

Conclusion and relevance Eculizumab was effective in C-TMA based on cellular and biochemical markers (platelets, LDH, creatinine). Changes in some parameters may not have been detected because of the small sample size. Two of six patients were in remission after 26W. The estimated cost for additional C-TMA–remission was 1 011 900€.

References and/or acknowledgements No conflict of interest.