Crizanlizumab Reduces Priapic Events in Men with Sickle Cell Disease

Alan Anderson, MD

Crizanlizumab was associated with a halved likelihood of priapic events among treated patients with sickle cell disease-related priapism, according to findings from a phase 2 trial.

In new data from the SPARTAN trial presented at the American Society of Hematology (ASH) 2022 Annual Meeting in New Orleans last week, a team of US investigators observed that the monoclonal antibody was associated with a reduction in priapic episodes over a half-year of treatment.

Presented by Alan Anderson, MD, of the Prisma Health-Upstate Comprehensive Sickle Cell Disease Program at University of South Carolina School of Medicine, the investigators conducted an interim analysis of SPARTAN to assess the efficacy and safety of crizanlizumab in patients with sickle cell disease suffering from priapism—a painful penil erection that occurs in more than one-third of adult males with sickle cell disease.

As Anderson and colleagues noted, priapism may occur from the underlying mechanism of microcapillary vaso-occlusion in these paitnets.

“To date, there is no effective sickle cell disease modifying drug proven to treat priapism,” they wrote. “Crizanlizumab is a monoclonal antibody that binds and blocks P-selectin; a key mechanistic component of the vaso-occlusive process. Based on the results of the SUSTAIN trial, crizanlizumab was approved by the US Food and Drug Administration to reduce the frequency of vaso-occlusive crises in sickle cell disease patients aged 16 years and older.”

The SPARTAN trial population included patients ≥12 years old with any genotype of sickle cell disease. Eligible patients had experienced ≥4 priapic episodes of ≥60 minutes in the 14 weeks leading up to the clinical trial. Patients additionally had to experience ≥3 priapic events during the 12-week screening period and ≥1 event within 4 weeks prior to initiating treatment.

Patients logged priapic events via electronic self-reporting and outcome surveys over 26 weeks, including details for the start and end date, sleep status, duration, non-pharmacological treatments, triggers, emergency department visits and pain intensity.

Investigators treated patients with 5.0 mg/kg intravenous infusion crizanlizumab at weeks 1 and 3, then every 4 weeks thereafter. The analysis’ primary endpoint was percent reduction from baseline in priapic event frequency over 26 weeks.

At the interim analysis cutoff of March 8, 2022, investigators had assessed 24 patients receiving ≥1 dose of crizanlizumab, and 3 patients who each missed 1 infusion. Approximately 70% of patients were aged 18 – 40 years old; median age was 29.5 years. All patients were African American. The most common genotype was HbSS (79.2%), and a majority of patients (58.3%) received hydroxyurea therapy prior to enrollment. Approximately 95% of patients reported priapism-associated pain.

Median baseline number of priapic events per 26 weeks was 51 per patient. After 26 weeks of treatment, investigators observed priapic event reduction in 17 of 24 patients (70.8%). Patients reported a median 53.1% reduction in events (95% CI, -73.4 to 9.3). The period of weeks 15 – 26 were associated with a greater median percent reduction from baseline (-72.7%; 95% CI, -94.0 to -37.1) than weeks 0 – 12 (-25.0%; 95% CI, -52.9 to 1.5).

Per subgroup analyses, patients with ≥22 baseline events experienced the greatest benefit of event reduction (-62.2%; 95% CI, -76.3 to -17.6). Crizanlizumab was associated with good tolerability; the 2 most common treatment-emergent adverse events included headache (16.7%) and fatigue (12.5%).

Anderson and colleagues concluded that sickle cell disease-related priapism was approximately halved among impacted patients treated with crizanlizumab over 26 weeks.

“There was a trend toward improved efficacy with a longer treatment period and in patients with a higher number of events at baseline,” they wrote. “Final results of the SPARTAN trial will provide more definitive conclusions regarding the efficacy of crizanlizumab in decreasing priapism.”

The study, “Interim Analysis of a Phase 2 Trial to Assess the Efficacy and Safety of Crizanlizumab in Sickle Cell Disease Patients with Priapism (SPARTAN),” was presented at ASH 2022.