In this edition of “How I Will Treat My Next Patient,” I highlight two recent drug approvals by the Food and Drug Administration – crizanlizumab for sickle cell patients with painful crises and zanubrutinib for mantle cell lymphoma (MCL) patients in relapse.
P-selectin is an adhesion molecule expressed on activated vascular endothelial cells and platelets. It is a key molecule in the initiation of leukocyte rolling on vessel walls and promotes firm attachment and extravasation to underlying tissues during inflammation. Up-regulation of P-selectin on endothelial cells and platelets contributes to the cell-cell interactions involved in the pathogenesis of sickle cell pain crises.
The SUSTAIN study was a multisite, placebo-controlled, randomized phase 2 trial of two different dosage levels of intravenous crizanlizumab (2.5 mg/kg or 5 mg/kg for 52 weeks), a humanized anti–P-selectin antibody, examining its effect on pain crises in patients with sickle cell disease. The primary endpoint was the annual rate of sickle cell pain crises, with a variety of clinically relevant secondary endpoints. The target population had 2-10 pain crises in the 12 months before enrollment. Patients on a stable dose of hydroxyurea for at least the most recent 3 months were allowed to enter, but if patients were not receiving hydroxyurea, it could not be initiated during the trial. Patients who were undergoing chronic red-cell transfusion therapy were excluded.
Among 198 enrolled patients, 35% did not complete the 52 weeks of treatment. Discontinuations were equally balanced among patients assigned to the high-dose, low-dose, and placebo cohorts. Adverse events associated with crizanlizumab included back pain, nausea, pyrexia, and arthralgia. Serious adverse events occurred in 55 patients, with 5 deaths, all of which were unrelated to treatment. Crizanlizumab did not augment hemolysis or bacterial infections.
In the efficacy analysis, patients receiving high-dose crizanlizumab had a median annual rate of 1.63 health care visits for sickle cell pain crises, compared with 2.98 visits for placebo patients (P = .01). In comparison with placebo, high-dose crizanlizumab also delayed the first pain crisis after starting treatment (4.1 months vs. 1.4 months), delayed the median time to a second pain crisis, and decreased the median number of pain crises annually.
More than twice as many high-dose crizanlizumab patients had no pain crisis episodes, compared with placebo patients. In general, differences were more striking in patients who were not taking hydroxyurea and who had non–hemoglobin SS disease. Differences in the primary endpoint between low-dose crizanlizumab and placebo were numerically, but not statistically, different.
How these results influence practice
It has been over 20 years since a new agent (hydroxyurea) was approved for sickle cell patients and, despite its use, sickle cell pain crises remain a frequent problem. Pain crises are associated with worse quality of life and increased risk of death. A promising advance is badly needed, especially in an era in which sensitivity to providers’ role in the opioid addiction crisis is highly scrutinized and may contribute to future undertreatment of pain episodes. This is especially true for patients from areas with high levels of opioid misuse.