Background
Phase 3, open-label, single-arm study (CARDINAL). N=24 patients with cold agglutinin disease (CAD) and a recent blood transfusion (within 6 months). CAD is a complement-mediated hemolytic anemia in which cold-reactive IgM autoantibodies activate the classical complement pathway, causing C3b-mediated extravascular hemolysis (primarily) with some intravascular hemolysis. Sutimlimab (Enjaymo): humanized monoclonal antibody inhibiting complement C1s, blocking the classical pathway upstream of C3 while sparing the lectin and alternative pathways.
Interventions and follow up
Treatment: Sutimlimab IV (6.5 g if <75 kg or 7.5 g if ≥75 kg) on days 0 and 7, then every 2 weeks for 26 weeks
Primary endpoint: Composite response (Hgb ≥12 g/dL or ≥2 g/dL increase from baseline, absence of transfusion, absence of prohibited medications)
Median follow-up: 26 weeks
Primary endpoint: Composite response (Hgb ≥12 g/dL or ≥2 g/dL increase from baseline, absence of transfusion, absence of prohibited medications)
Median follow-up: 26 weeks
Results
Composite primary response: 13/24 (54%)
Mean Hgb increase (baseline to weeks 23–26): +2.26 g/dL; P<.001
Bilirubin normalization: 71% by week 3
Transfusion avoidance: 83% of patients avoided transfusion during treatment
FACIT-Fatigue score improvement: +10.9 points (clinically meaningful)
Mean Hgb increase (baseline to weeks 23–26): +2.26 g/dL; P<.001
Bilirubin normalization: 71% by week 3
Transfusion avoidance: 83% of patients avoided transfusion during treatment
FACIT-Fatigue score improvement: +10.9 points (clinically meaningful)
Adverse events
Most common: Headache 29%, Raynaud's phenomenon 21%, arthralgia 17%
Serious AEs: 3 patients
Meningococcal infections / thromboembolic events: None (vaccination required)
Respiratory tract infections: Common, consistent with classical-pathway inhibition and impaired opsonization of encapsulated bacteria
Anti-drug antibodies: None detected
Serious AEs: 3 patients
Meningococcal infections / thromboembolic events: None (vaccination required)
Respiratory tract infections: Common, consistent with classical-pathway inhibition and impaired opsonization of encapsulated bacteria
Anti-drug antibodies: None detected
Conclusions
Sutimlimab rapidly and substantially reduced hemolysis in CAD patients who had recently required transfusion, increasing hemoglobin, normalizing bilirubin, avoiding transfusions, and improving fatigue, establishing a targeted complement inhibitor specifically for CAD.
Key Limitations
Small, open-label, single-arm study (n=24) with no placebo control. Restricted to recently-transfused CAD patients, limiting generalizability. 26-week primary follow-up; durability and chronic-infection risk uncertain. Hemolysis recurs on discontinuation (rebound). Surrogate endpoints.
Clinical Context
Supported FDA approval of Enjaymo (Feb 2022), first therapy specifically for CAD, to decrease the need for RBC transfusion. Classical-pathway C1s inhibition complements supportive cold-avoidance measures; meningococcal/encapsulated-organism prophylaxis advised given complement blockade.
References