Transfusion Requirements in Adult Patients with Paroxysmal Nocturnal Hemoglobinuria with or without a History of Bone Marrow Disorder Receiving Ravulizumab and Eculizumab: Results from a Phase 3 Non-Inferiority Study Extension

Background: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare and life-threatening hematologic disorder leading to hemolytic anemia, which can occur concomitantly with bone marrow disorders (BMD), such as aplastic anemia (AA) and myelodysplastic syndrome (MDS). Accordingly, patients with PNH often require red blood cell (RBC) transfusions to treat anemia due to hemolysis or bone marrow failure. After demonstrating a non-inferior efficacy and safety profile in two of the largest clinical trials to date, ravulizumab was approved as a treatment for adults with PNH, including patients with an underlying history of bone marrow disease, who are transfusion dependent or independent.

Aims: To assess the efficacy of ravulizumab in patients with PNH with or without an underlying pathology of AA or MDS, and to investigate the impact of ravulizumab on transfusion burden as measured by number of transfusions and total packed RBC (pRBC) units transfused over a 52-week period.

Methods: This phase 3 multicenter, randomized, active-controlled, open-label study (study 301, NCT02946463) enrolled complement-inhibitor-naïve patients with PNH. Patients were aged ≥ 18 years with a confirmed diagnosis of PNH by flow cytometry and lactate dehydrogenase (LDH) level ≥ 1.5x the upper limit of normal (ULN; 246 U/L). Patients received either ravulizumab or eculizumab for 26 weeks; after which all patients received ravulizumab from week 26 to week 52. Efficacy outcomes included the proportion of patients achieving transfusion avoidance (TA), number of pRBC units transfused and the number of pRBC or whole blood transfusions (WBT) received from baseline to 26 and 52 weeks of treatment. In this retrospective analysis, outcomes were analysed for the following subgroups: AA, MDS or no BMD (medical history of AA or MDS was determined by the investigator at screening). Descriptive statistics were calculated for continuous (means) and categorical variables (numbers and percentages). Formal hypothesis testing for significance between treatment groups was not performed.

Results: Of the 246 patients included in the study, 79 had a history of AA (32.1%) and 13 (5.3%) had a history of MDS. Baseline characteristics were comparable between treatment groups. From baseline to week 26, a comparable proportion of patients with AA achieved TA to those with no BMD; 75.6% for patients with AA and no BMD receiving ravulizumab, and 60.5% and 73.7% for patients with AA and no BMD receiving eculizumab, respectively (Table 1). Importantly, TA was maintained through 52 weeks, with similar proportions of patients with AA (87.1‒91.3%) maintaining TA to patients without BMD (85.7‒91.5%). More specifically, 65.9% of patients with AA and 69.2% of patients without BMD achieved TA through 52 weeks of ravulizumab treatment, and 55.3% and 63.2% of patients with AA and without BMD, respectively, achieved TA on eculizumab followed by ravulizumab. The proportion of patients with MDS who achieved TA appeared numerically lower compared with patients with AA or no BMD, however, this subgroup sample size was small. Furthermore, a lower proportion of patients on ravulizumab with AA or MDS received any transfusion from baseline to weeks 26 and 52 compared with those treated with eculizumab followed by ravulizumab: for week 26, 24.4% and 57.1% for ravulizumab versus 39.5% and 100.0% for eculizumab in patients with AA and MDS, respectively, and for week 52, 29.3% and 57.1% for patients with AA and MDS receiving ravulizumab for 52 weeks versus 44.7% and 100.0% for patients with AA and MDS treated with eculizumab followed by ravulizumab. In addition, ravulizumab-treated patients with AA or MDS had numerally fewer transfusions and units of pRBC/WBT compared with those who received eculizumab followed by ravulizumab. Overall, the exploratory nature of the analysis and small sample size means that interpretation of the data is limited.

Conclusions: This analysis demonstrates that majority of patients with PNH and AA who received ravulizumab avoided the need for transfusion up to 52 weeks of treatment. Patients treated with ravulizumab for the 52-week period had numerically fewer transfusions and units of pRBC/WBT transfused compared with patients who received eculizumab followed by ravulizumab. Overall, these findings support the use of ravulizumab in complement-inhibitor-naïve patients with PNH, with or without a history of BMD.