CAD is a rare, chronic type of autoimmune hemolytic anemia, where hemolysis is driven by classical complement pathway (CP) activation. Complement activation assures rapid initiation of the complement cascade as part of an early immune response and inflammation. A proinflammatory state secondary to complement activation has been demonstrated in other hemolytic disease such as paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome (Weitz et al. Thromb Res. 2012; Cofiell et al. Blood. 2015). Complement activation stimulates cytokine production (tumor necrosis factor, interleukin 6 [IL-6], IL-8, IL-17) via anaphylatoxins C3a and C5a and increases vascular inflammatory markers, consistent with complement-mediated inflammation (Landsem et al. Clin Exp Immunol. 2017; Cofiell et al. Blood. 2015). In patients with chronic fatigue syndrome, complement activation is associated with higher levels of fatigue (Sorensen et al. J Allergy Clin Immunol. 2003) and inflammatory cytokine activity correlates with the severity of fatigue symptoms (Montoya et al. PNAS. 2017). In addition, IL-6 plays a more dominant role in immune stimulation, particularly during chronic inflammation stress such as rheumatoid arthritis (Choy et al. Rheumatology. 2018).

In CAD, CP activation and chronic inflammation may contribute to patient fatigue, apart from anemia. CP activation resulting in a proinflammatory state has not been formally studied in CAD. The interplay between complement-mediated inflammation and fatigue also has not been previously explored in patients with CAD. In the Cardinal study (NCT03347396), efficacy and safety of the humanized monoclonal anti-C1s antibody, sutimlimab (formerly BIVV009), was evaluated in patients with CAD and recent history of blood transfusion. Here we summarize the results of inflammatory cytokine expression for IL-6 and IL-10 and their relation to fatigue over the Part A 26-week treatment period of Cardinal.


In Cardinal Part A, patients with CAD received intravenous doses of sutimlimab on Days 0 and 7, and biweekly infusions thereafter. Patients weighing <75 kg and ≥75 kg received a 6.5 g and 7.5 g dose, respectively. Cytokine levels for IL-6 and IL-10 were assessed in patients with available serum samples. Cytokine profiles and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scores were evaluated from baseline to follow-up time points at Weeks 1, 3, 5, and 25, as represented by the treatment assessment time point (TAT) after initiating sutimlimab treatment. Summary statistics describing IL-6, IL-10, and FACIT-F changes at each week were reported.


Mean IL-6 level (mean pg/mL [standard error of the mean (SEM)]) steadily decreased from baseline (3.21 [0.958]; normal values IL-6 <3.2 pg/mL) to follow up at all time points after initiating sutimlimab treatment (Figure 1), showing rapid onset and durable pattern of decline as early as Week 1 (2.70 [0.839]). Mean IL-6 level was reduced by more than half by Week 3 (1.56 [0.297]), slightly rose at Week 5 (1.88 [0.383]), and was lowest at TAT (1.31 [0.201]). Mean IL-10 level (pg/mL [SEM]) also decreased in a time-dependent manner from baseline (1.36 [0.310]) initially at Week 1 (0.99 [0.250]). Mean IL-10 slightly increased at Week 3 (1.07 [0.306]), but dropped at Week 5 (0.83 [0.142]) and was lowest by TAT (0.82 [0.129]) with sutimlimab treatment (Figure 2). At baseline, mean (SEM) FACIT-F score was 32.5 (2.266) (Figures 1-2). Patient FACIT-F scores showed early and late improvements with mean score increases at Week 1 (39.67 [1.741]), Week 3 (40.70 [1.543]), Week 5 (43.75 [1.192]), and at TAT (41.86 [1.958]). Decreased inflammation, as demonstrated by IL-6 and IL-10 activity, occurred concurrently with FACIT-F score improvements over time.


In Cardinal Part A, decrease from baseline to TAT in mean proinflammatory cytokine IL-6 and regulatory cytokine IL-10 levels were observed during sutimlimab treatment, highlighting the influence of complement inhibition on inflammation in CAD. Improved FACIT-F scores are concurrent with sutimlimab treatment and inhibition of the CP. Concurrent inverse changes were noted between select inflammatory cytokines and improvements in patients' fatigue, suggesting complement-mediated inflammation may additionally contribute to manifestation of fatigue in patients with CAD.


Weitz:Apellis: Consultancy, Honoraria; Alexion: Consultancy, Honoraria, Speakers Bureau. Ueda:Novartis: Honoraria; Alexion Pharmaceuticals: Consultancy, Honoraria, Research Funding; Sanofi: Consultancy, Honoraria. Shafer:Sanofi: Current Employment. Su:Sanofi: Current Employment. Foster:Sanofi Genzyme: Current Employment. Storek:Sanofi: Current Employment. Patel:Sanofi: Current Employment.

Author notes


Asterisk with author names denotes non-ASH members.