Survival in adults with high-risk TA-TMA: a comparative analysis of narsoplimab vs supportive care

Abstract

Hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) is a potentially fatal multisystem complication of hematopoietic cell transplantation for which there is no approved treatment. In a single-arm study (NCT02222545), narsoplimab treatment for TA-TMA demonstrated a median overall survival (OS) of 274 days from date of diagnosis. Here, we compare OS observed in 2 cohorts treated with narsoplimab to OS in a well-matched external control to test survival benefit in patients with high-risk TA-TMA. OS in patients (aged ≥16 years) with high-risk TA-TMA treated with narsoplimab in a single-arm, open-label study (NCT02222545) or in the narsoplimab expanded access program (EAP; NCT04247906) was compared with OS in a control group with high-risk TA-TMA from the Kyoto Stem Cell Transplantation Group (KSCTG) registry. Narsoplimab-treated patients in the single-arm study (N = 28) had a fourfold reduction in risk of mortality compared with patients from the KSCTG registry (N = 111; hazard ratio [HR], 0.25; 95% confidence interval [CI], 0.19, 0.34; P < .0001). Similarly, in high-risk patients treated with narsoplimab in the EAP (N = 49), mortality risk was significantly lower than among high-risk patients from the KSCTG registry (N = 121; HR 0.38; 95% CI 0.28, 0.51; P < .0001). When narsoplimab-treated patients from the single-arm study and the EAP (N = 77) were compared with KSCTG patients, the HR for mortality was 0.28 (95% CI, 0.22, 0.37; P < .0001). In conclusion, in patients with high-risk TA-TMA, narsoplimab treatment significantly reduced mortality relative to a well-matched external control group who did not receive narsoplimab. These results support narsoplimab as a potential therapeutic option for TA-TMA.