MAS activity, as defined by physician’s assessment, and laboratory features of MAS before, during and after emapalumab treatment
| Screening (n=14) | Baseline (n=14) | Week 2 (n=14) | Week 4 (n=14) | Week 8 (n=14) | |
| Physician assessment of MAS activity*, cm, median (range) | 8.3 (2.0–10.0) | 8.0 (2.0–10.0) | 2.3 (0.0–9.5) | 0.3 (0.0–6.5) | 0 (0.0–1.0) |
| Ferritin, ng/mL, median (range) | 19 865 (367–192 584) | 25 709 (716–192 584) | 1410 (65–29 099) | 180 (22–18 430) | 55 (4–561) |
| Increased, n (%)† | 13 (93) | 14 (100) | 9 (64) | 2 (14) | 0 (0) |
| WBCs, 109/L, median (range) | 5.8 (1.0–25.7) | 5.1 (0.9–25.7) | 8.4 (0.9–32.6) | 12.3 (2.4–34.7) | 9.5 (4.8–22.6) |
| Decreased, n (%)‡ | 6 (43) | 7 (50) | 4 (29) | 1 (7) | 1 (7) |
| Platelets, 109/L, median (range) | 152 (48–546) | 112 (52–558) | 284 (55–590) | 336 (104–591) | 383 (214–915) |
| Decreased, n (%)‡ | 6 (43) | 9 (64) | 4 (29) | 2 (14) | 0 (0) |
| Aspartate aminotransferase, U/L, median (range) | 244 (26–3814) | 190 (19–2039) | 34 (5–146) | 29 (16–100) | 28 (15–52) |
| Increased, n (%)§ | 12 (86) | 10 (71) | 3 (21) | 1 (7) | 0 (0) |
| Alanine aminotransferase, U/L, median (range) | 190 (139–3179) | 302 (70–1492) | 61 (18–327) | 45 (23–195) | 28 (7–59) |
| Increased, n (%)§ | 14 (100) | 14 (100) | 6 (43) | 5 (35.7) | 0 (0) |
| LDH, U/L, median (range) | 1699 (859–12 734) | 1502 (588–12 734) | 518 (283–1572) | 592 (277–810) | 497 (306–741) |
| Increased, n (%)§ | 13 (100) | 13 (93) | 6 (43) | 4 (29) | 2 (14) |
| Fibrinogen, mg/dL, median (range) | 230 (137–341) | 174 (70–465) | 244 (145–515) | 279 (200–460) | 337 (190–460) |
| Decreased, n (%)¶ | 0 (0) | 1 (7) | 0 (0) | 0 (0) | 0 (0) |
*MAS activity was based on a 10 cm visual analogue scale, with scores ranging from 0 to 10 and higher score indicating higher activity.
†Increased ferritin was defined as ferritin >684 ng/mL as per 2016 Classification Criteria for MAS complicating sJIA.23
‡Decreased white blood cell and platelet were defined as counts below the lower limit of normal for age of local laboratory.
§Increased alanine aminotransferase, aspartate aminotransferase and LDH were defined as values above 1.5 the upper limit of normal range of local laboratory.
¶Decreased fibrinogen was defined as fibrinogen <100 mg/dL.
LDH, lactate dehydrogenase; MAS, macrophage activation syndrome; WBC, white blood cells.