Pharmacokinetics, pharmacodynamics, safety, and efficacy of crizanlizumab in patients with sickle cell disease

The challenge of clinical end points in sickle cell disease

As most patients with sickle cell disease (SCD) do not have access to curative therapies, the availability of drug therapies that can modify disease severity remains highly desirable. Despite an increased understanding of the pathophysiology of SCD, only 4 drugs are approved by the US Food and Drugs Administration. Most drug trials in SCD have involved the use of acute pain episodes as the primary clinical end point. These studies have typically been to prevent or shorten the duration of such episodes. To date, no drug has received regulatory approval for shortening the duration of acute vaso-occlusive complications, likely highlighting the complex pathophysiology of acute pain episodes. Trials to prevent acute pain episodes have largely evaluated those episodes requiring health care use as a surrogate end point. However, with differences in culture and health care practices among countries, health care use may not reliably predict clinically important effects on acute pain episodes. This article discusses issues related to the use of health care use as the primary end point for prevention trials of acute pain episodes and highlights the importance of evaluating patient-reported outcomes as well as other SCD-related complications as outcome measures.

Using disease-modifying therapies in sickle cell disease

As curative therapy using allogeneic hematopoietic stem cell transplantation as well as gene therapy and gene editing remains inaccessible to most patients with sickle cell disease, the availability of drug therapies that are safe, efficacious, and affordable is highly desirable. Increasing progress is being made in developing drug therapies based on our understanding of disease pathophysiology. Four drugs, hydroxyurea, L-glutamine, crizanlizumab, and voxelotor, are currently approved by the US Food and Drug Administration, with multiple others at various stages of testing. With the limited efficacy of individual agents, combinations of agents will likely be required for optimal outcomes.

Crizanlizumab in sickle cell disease

Vaso-occlusion in sickle cell disease (SCD) leads to a myriad of manifestations driving morbidity and mortality in patients with SCD. Increased leucocyte adhesion and P-selectin expression on platelets and endothelial cells is an inciting event that leads to obstruction of microcirculation by adhesion with rigid sickled red blood cells. Crizanlizumab is a first-in-class monoclonal antibody that inhibits P-selectin and has been shown to decrease the frequency of vaso-occlusive pain crises in patients with SCD in clinical trials. The role of crizanlizumab in other manifestations of SCD still needs further investigation.

The invisible string of coagulation, complement, iron, and inflammation in sickle cell disease

PURPOSE OF REVIEW

This review provides an update on recent advances in mechanistic studies of thromboinflammatory mechanisms that contribute to the disease pathology in sickle cell disease (SCD). There is a focus on novel pathways, clinical relevance, and translational potential of these findings. We hope to encourage more advances in this area to reduce organ damage in young patients prior to gene therapy, and to serve the aging SCD patient population.

RECENT FINDINGS

Novel insights into the roles of neutrophils, the ADAMTS-13/VWF axis, oxidative stress, and the intrinsic coagulation cascade, as well as relevant clinical trials, are discussed.

SUMMARY

Several studies implicate dysregulation of the ADAMTS-13/VWF axis as playing a major role in vaso-occlusive events (VOE) in SCD. Another highlight is reducing iron overload, which has beneficial effects on erythrocyte and neutrophil function that reduce VOE and inflammation. Multiple studies suggest that targeting HO-1/ROS in erythrocytes, platelets, and endothelium can attenuate disease pathology. New insights into coagulation activation identify intrinsic coagulation factor XII as a central regulator of many thromboinflammatory pathologies in SCD. The complement cascade and modulators of neutrophil function and release of neutrophil extracellular traps are also discussed.