Conference Coverage

Oral voxelotor improves hemoglobin in sickle cell disease



– The investigational oral agent voxelotor induced rapid and sustained improvements in hemoglobin and hemolysis in both children and adults with sickle cell disease (SCD), follow-up results from the phase 3 HOPE trial show.

Dr. Jo Howard of King's College, London. Neil Osterweil/MDedge News

Dr. Jo Howard

Among 274 patients aged 12-59 years, those who were randomly assigned to receive voxelotor at a dose of 1,500 mg daily had significantly better hemoglobin responses – defined as an increase of more than 1.0 g/dL from baseline – than did patients assigned to placebo, reported Jo Howard, MD, of Guy’s and St. Thomas’ NHS Foundation Trust and King’s College in London.

Voxelotor improves hemoglobin and reduces hemolysis in patients with sickle cell disease. This has the potential to reduce the morbidity in sickle cell disease and to improve the life of our patients,” she said at a briefing prior to her presentation of the data at the annual congress of the European Hematology Association.

There were no new safety signals and patients tolerated voxelotor well, she added.

The study was published simultaneously in the New England Journal of Medicine.

Voxelotor is a novel oral agent that increases hemoglobin’s affinity for oxygen by inhibiting hemoglobin polymerization and sickling of red blood cells, which if unchecked lead to serious consequences, such as chronic anemia and hemolysis, and subsequent organ damage, vaso-occlusion, stroke, or premature death.

In the HOPE (Hemoglobin Oxygen Affinity Modulation to Inhibit HbS Polymerization) trial, investigators enrolled 274 adolescents and adults with SCD and randomized them on a 1:1:1 basis to receive voxelotor at doses of either 1,500 mg or 900 mg daily, or placebo.

Approximately two-thirds of the patients were receiving hydroxyurea at baseline.

In a per-protocol analysis, 59.5% of patients who received the 1,500-mg dose of voxelotor had a hemoglobin response (P less than .001 compared with baseline), as did 38% of patients in the 900-mg group (P less than .001). Among patients assigned to placebo, however, just 9.2% had a hemoglobin response, a difference that was not statistically significant.

In an intention-to-treat analysis, in which patients who did not complete the study were considered to be nonresponders, the respective rates of hemoglobin response were 51.1%, 32.6%, and 6.5%.

The difference between the 1,500-mg dose and placebo was significant (P less than .001). The difference between the 900-mg group and placebo was not statistically significant.

Hemoglobin levels of 10 g/dL or higher at week 24 were seen in 41% of the participants in the 1,500-mg group, 20% in the 900-mg group, and 9% in the placebo group.

Patients on voxelotor had an improvement in hemoglobin, whether or not they were on hydroxyurea, and those with hemoglobin either below or above 7 g/dL at baseline all had an increase in hemoglobin.

The annualized adjusted incidence rate of vaso-occlusive crises was similar in the two voxelotor groups (2.77 for the 1,500-mg dose and 2.76 for the 900-mg group) – both lower than in the placebo group (3.19).

Among patients who had two or more vaso-occlusive crises within the previous year, the respective annualized incidence rates were 2.88, 3.39, and 3.50.

There was a trend toward reduced incidence of crises with voxelotor over time, Dr. Howard said.

Grade 3 or greater adverse events occurred in 26% of patients in the 1,500-mg group, 23% in the 900-mg group, and 26% in the placebo group. The most common adverse events were headache and diarrhea.

“The data presented support the achievement of the stated primary endpoint in the HOPE trial, which was to reduce anemia and hemolysis. The hemoglobin response and reduction in hemolysis observed with an orally administered, once-daily medication with side effects that minimally affect lifestyle may make voxelotor a promising advancement in the management of sickle cell disease if approved by the [Food and Drug Administration],” Alexis Thompson, MD, MPH, of Northwestern University, Chicago, noted in an editorial accompanying the study in the New England Journal of Medicine.

Global Blood Therapeutics funded the study. Dr. Howard reported consultant/advisory board activity for the company. Dr. Thompson reported grants and/or personal fees from other companies.

SOURCE: Vichinsky E et al. EHA Congress, Abstract S147. N Engl J Med. 2019 Jun 14. doi: 10.1056/NEJMoa1903212.

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