HU noninferior to transfusion for stroke prevention in SCD

“Commensurately, the hemoglobin F rises as a protection. The neutrophil count and reticulocyte count drops, and those curves [counts in the HU and transfusion arms] diverge fairly quickly. The serum ferritin [curves] diverged as well.”

Early termination and noninferiority

Interim data analyses were scheduled to take place after one-third of the patients had exited the study and after two-thirds had exited. The first interim analysis demonstrated noninferiority, and the trial was closed early. An analysis was repeated after half of the patients had exited the study, and the trial was terminated.

At that point, 42 children had completed 24 months of treatment in the transfusion arm, 11 patients had truncated treatment, and 8 had early exits. Forty-one patients had completed 24 months of therapy in the HU arm, 13 had truncated treatment, and 6 had early exits.

The final TCD velocity (mean ± standard error) was 143 ± 1.6 cm/sec in the transfusion arm and 138 ± 1.6 cm/sec in the HU arm. The P value for noninferiority (in the intent-to-treat population) was 8.82 x 10^-16. By post-hoc analysis, the P value for superiority was 0.023.

Secondary endpoints

There were 29 new neurological events during the trial—12 in the transfusion arm and 17 in the HU arm. There were no new strokes, but there were 6 new transient ischemic attacks—3 in each arm.

There were no new cerebral infarcts in either arm. But there was 1 new progressive vasculopathy in the transfusion arm. And 1 child in the transfusion arm was withdrawn from the study for increasing TCD (>240 cm/sec).

Iron overload improved more in the HU arm than the transfusion arm, with a greater average change in both serum ferritin (P<0.001) and liver iron concentration (P=0.001).

Serious adverse events were more common in the HU arm than the transfusion arm—23 events in 9 patients and 10 events in 6 patients, respectively. But none of these events were thought to be related to study treatment or procedures.

The most common serious adverse event in both groups was vaso-occlusive pain—11 events in 5 HU-treated patients and 3 events in 1 transfusion-treated patient.

Dr Ware noted that there were no secondary leukemias associated with HU in this trial, and there is “a cumulative body of evidence” spanning 20 years that suggests the drug is not carcinogenic in this patient population.

*Data in the abstract differ from data presented at the meeting.