Emapalumab in Primary Hemophagocytic Lymphohistiocytosis

To the Editor: New and affordable treatments for primary hemophagocytic lymphohistiocytosis (pHLH) are valuable. However, the study by Locatelli et al. (May 7 issue) 1 does not present convincing data for strong efficacy of emapalumab in patients with pHLH. The data reveal that among a total of 34 patients, including 27 who had previously received treatment and 7 who had not, among those who received treatment with emapalumab and dexamethasone, only 14 (41%) survived without additional treatment with etoposide, antithymocyte globulin, alemtuzumab, or some combination thereof; there were 9 surviving patients who received such therapy (Table 1). Moreover, 2 patients survived . . .