Crizanlizumab 5.0 Mg/Kg Exhibits a Favorable Safety Profile in Patients with Sickle Cell Disease: Pooled Data from Two Phase II Studies

Background: Crizanlizumab, a humanized monoclonal antibody that binds P-selectin and blocks interaction with its ligands (including leukocyte PSGL-1), is under investigation for preventing vaso-occlusive crises (VOCs) in individuals with sickle cell disease (SCD). Crizanlizumab 5.0 mg/kg was shown to significantly reduce the median annual rate of VOCs by 45.3% versus placebo (Hodges-Lehmann median absolute difference of -1.01 vs placebo, 95% CI [-2.00, 0.00]; P=0.01) (Ataga et al. N Engl J Med 2017).

Aims: This pooled analysis evaluated key safety endpoints in patients treated with the recommended dose of crizanlizumab (5.0 mg/kg monthly, following 2 loading doses in the first month).

Methods: Data were pooled from 2 Phase II studies of SCD patients (any genotype) with a history of VOCs leading to a healthcare visit. SUSTAIN (NCT01895361) was a randomized, placebo-controlled study in patients aged 16-65 years who had experienced 2-10 VOCs in the previous 12 months. SOLACE-adults (A2202) is an ongoing, open-label PK/PD study (NCT03264989) in patients aged 16-70 years who had experienced at least 1 VOC in the previous 12 months; data cut-off for this analysis was 1 March 2019. Adverse events (AEs) were evaluated based on MedDRA v21.1. AE severity in SOLACE was assessed based on CTCAE v5; in SUSTAIN, severity was collected as mild/moderate/severe but then recategorized for this analysis to a 5-point scale similar to CTCAE grading. AEs of special interest (ie known class effects; AEs identified preclinically or in previous studies; or potentially relevant based on the mechanism of action of crizanlizumab) were also evaluated and included infections, infusion-related reactions (IRRs) and hemostatic effects. As monoclonal antibodies can induce an immune response, anti-drug antibodies (ADAs) were also measured.

Results: In total, 111 patients (SUSTAIN, n=66; SOLACE, n=45) received crizanlizumab 5.0 mg/kg: 59 females (53.2%) and 52 males (46.8%). Median age was 29 years (range 16-65). The most common SCD genotypes were HbSS (n=73; 65.8%) and HbSC (n=19; 17.1%), and 75 patients (67.6%) were receiving hydroxyurea (HU). Most patients (n=67; 60.4%) had 1-4 VOCs in the previous 12 months. Median duration of exposure to crizanlizumab was 46 weeks (range 4-58).

At least 1 AE was reported in 94 patients (84.7%), the most common (≥15%) being headache (n=22; 19.8%), nausea (n=18; 16.2%) and back pain (n=17; 15.3%). AEs were mild/moderate (grade 1 or 2) and resolved spontaneously in most patients; 23 patients (20.7%) had a grade 3 AE and 1 (0.9%) had a grade 4 AE (neoplasm). At least 1 serious AE was reported in 24 patients (21.6%); serious AEs with a suspected relationship to crizanlizumab were reported in 6 patients (5.4%). Twenty-eight patients (25.2%) discontinued treatment prematurely (n=23 in SUSTAIN, n=5 to date in SOLACE): discontinuations due to AEs (bradycardia and breast cancer) occurred in 2 patients (1.8%); neither was considered related to crizanlizumab. There were 2 on-treatment deaths in SUSTAIN, but neither were considered related to crizanlizumab.

Infection events were reported in 51 patients (45.9%), the most common (≥5%) being upper respiratory tract infection (n=13, 11.7%) and urinary tract infection (n=11, 9.9%). There were no grade 4 infections and none led to discontinuation. Data suggest no increased risk or severity of infection in studies with crizanlizumab. Two patients (1.8%) experienced IRRs; the events were not serious and did not lead to discontinuation. Bleeding events were rare, with most observed hemostatic AEs being abnormal laboratory parameters occurring only once. Treatment-induced ADAs were transiently detected in 1 patient (0.9%) and spontaneously resolved. There were no clinically relevant laboratory (hematology, biochemistry, liver) or ECG abnormalities, or vital sign changes, and no notable differences in the AE incidence rates by gender, ethnicity or HU use.

Conclusions: This pooled analysis shows that crizanlizumab 5.0 mg/kg was well tolerated, with a favorable safety profile, in patients with SCD and a history of VOCs. Most AEs were mild/moderate, and discontinuations due to AEs were infrequent. The immunogenic potential of crizanlizumab appears low and there is currently no evidence for an increased risk of infection or bleeding. SOLACE-adults and SOLACE-kids (6 months to <18 years) are ongoing, and the randomized Phase III STAND trial is recruiting.