Early Evaluation of the Use of Crizanlizumab in Sickle Cell Disease: A National Alliance of Sickle Cell Centers Study

Background: Vaso-occlusive crises (VOC) are the most common acute complication of sickle cell disease (SCD). Crizanlizumab, an anti-P-selectin monoclonal antibody, is an FDA-approved disease-modifying therapy (DMT) for SCD patients (pts) aged ≥16 yrs to reduce the frequency of VOC. To better understand its use and impact, the National Alliance for Sickle Cell Centers (NASCC) conducted a retrospective study of pts prescribed crizanlizumab from 11/2019-6/30/2021. NASCC is a non-profit organization formed to support SCD centers in delivering quality comprehensive care by setting and adopting specific standards and advocating for improved health outcomes in SCD. This study describes the largest real-world cohort of pts treated with crizanlizumab.

Methods: This is a two-part study. Part 1 was to evaluate NASCC center crizanlizumab practice and to summarize data on insurance approval and the frequency of drug discontinuation. Part 2 includes pt level data to evaluate reasons for discontinuation and acute care utilization pre and post therapy. Acute care use includes day hospital/infusion, emergency department visits, and hospitalizations for VOC (excluding COVID-19). The index date for each pt is defined as the 1st crizanlizumab infusion date. Chart review (electronic health records) was used to identify all acute care visits 12 months pre-index and ≤12 months post index. Acute care data will be analyzed in aggregate.

Evaluation of center-specific use of crizanlizumab, time to initial site level formulary approval and drug discontinuation were analyzed. Pt level data collection is ongoing to include sufficient time post index date. VOC characteristics will be summarized using medians, median differences (pre/post treatment), and 95% confidence intervals. Additional evaluation of effectiveness of crizanlizumab will include analysis based on number of doses received, pre-treatment VOC burden, concomitant hydroxyurea (HU) use and genotype.

Results: Data includes pts prescribed crizanlizumab at 11 NASCC centers. Site- formulary approvals to use crizanlizumab varied from 12/2019-12/2020. As a result, the 1st pt to receive treatment at each site varied from 1/15/2020-1/20/2021. Mean time from site-level approval to first infusion was 77 days (range: 0-394). Over 50% of sites received insurance denials mainly due to "insufficient medical necessity" or "medication not covered by the prescription plan." Sites were able to successfully appeal denials for 71% of pts (Table 1).

Treatment Delivery: Each site gives infusions over 30 minutes and the majority (64%) do not use pre-medication unless pts had reactions. Some sites use diphenhydramine/acetaminophen (3) or normal saline and ketorolac (1). All sites prescribe crizanlizumab to pts of all SCD genotypes.

Pts Treated: 297 pts were prescribed crizanlizumab of whom 238 received ≥ 1 infusion. There was variation in number of pts/site (range 6-73, mean 21) due to time to site-level approval, insurance and pt population. Of these 238, 75 pts (32%) discontinued treatment (0-17 pts/site). Sites reported pts perceived lack of improvement or feeling their overall pain was increased, transportation issues and infusion related reactions (IRRs) characterized by pain as some of the reasons for discontinuation. Evaluation of real-world efficacy measured by changes in acute care utilization, including sub-analysis by genotype, pre-treatment VOC burden and concomitant HU use, are pending sample size dependent feasibility.

Discussion: This is the first multi-center real-world analysis of crizanlizumab. Findings demonstrate some insurance barriers to therapy. The majority of pts who initiated crizanlizumab have remained on therapy; however, 1/3 of pts had lack of effect or barriers to care. Pt level data will include characteristics related to treatment failure or IRR. Improving the understanding of phenotype-specific response to novel therapies is essential in SCD.

Conclusion: Post-approval therapies for rare diseases must undergo real-world evaluation to ensure study results translate to the community. NASCC uses defined criteria for multidisciplinary care for Alliance inclusion and findings reflect the use of DMT in such centers. This is the first NASCC study of DMT in SCD. Part 2 of the study will give early insights into the effectiveness of crizanlizumab; long term follow-up is needed for a full understanding of its utility in SCD.

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