ESA benefits lower-risk MDS patients

Ten percent (n=5) of placebo-treated patients and 2% (n=2) of darbepoetin alfa-treated patients had a dose withheld due to an AE. Two percent (n=1) and 3% (n=3) of patients, respectively, had a dose withheld for “other” reasons (noncompliance, investigator decision, and no investigational product on site).

During the 48-week open-label period of the study, 81% (102/126) of patients who received darbepoetin alfa increased their dose frequency from every 3 weeks to every 2 weeks. Dr Platzbecker said this suggests the optimal dose of the drug was not achieved during the 24-week double-blind period of the study.

Efficacy

During the 24-week double-blind period, there was a significant difference between the treatment arms with regard to RBC transfusions. The transfusion incidence was 59.2% (29/49) in the placebo arm and 36.1% (35/97) in the darbepoetin alfa arm (P=0.008).

During the 48-week open-label period, the incidence of RBC transfusion was 50.8% (64/126) among patients receiving darbepoetin alfa.

During the 24-week double-blind period, 11 patients (14.7%) in the darbepoetin alfa arm had an erythroid hematologic improvement (HI-E), but none of the patients in the placebo arm had such an improvement.

All 11 patients with HI-E had a baseline serum erythropoietin level less than 100 mU/mL, 1 of the patients had 2 RBC units transfused in the 16 weeks prior to randomization, but none had transfusions in the 8 weeks prior to randomization. Four of the patients had a dose withheld due to having hemoglobin levels greater than 12 g/dL.

During the 48-week open-label period, the HI-E rate was 34.7% (34/98) among patients receiving darbepoetin alfa.

Dr Platzbecker said the nature of the HI-E criteria likely underestimated the clinical benefit of darbepoetin alfa in this trial, and this was further complicated by the trial design. Specifically, hemoglobin was measured every 3 weeks, some patients may have had their doses reduced even if they were still anemic, and the optimal dose of darbepoetin alfa was likely not given during the double-blind period (as evidenced by the increase in doses during the open-label period).

For these reasons, Dr Platzbecker and his colleagues are exploring alternative response analyses to determine if there were additional patients who received a clinical benefit from darbepoetin alfa but did not meet HI-E criteria.

Safety

During the 24-week double-blind period, 4.2% (n=2) of patients in the placebo arm and 3.1% (n=3) in the darbepoetin alfa arm had AEs that led to treatment discontinuation. In the placebo arm, these events were pulmonary hypertension and renal failure. In the darbepoetin alfa arm, the events were pulmonary thrombosis, thrombocytopenia, and increased blast cell count.

The incidence of grade 3 or higher AEs was 27.1% (n=13) in the placebo arm and 15.3% (n=15) in the darbepoetin alfa arm. The incidence of grade 4 or higher AEs was 12.5% (n=6) and 5.1% (n=5), respectively. And the incidence of serious AEs was 16.7% (n=8) and 11.2% (n=11), respectively.

The incidence of fatal AEs was 4.2% (n=2) and 1% (n=1), respectively, but none of these were treatment-related. The deaths in the placebo arm were due to cardiac failure and cerebral hemorrhage, while the death in the darbepoetin alfa arm was due to hemorrhagic proctitis.

One patient in the darbepoetin alfa arm experienced a treatment-related serious AE.

AEs occurring at least 5% more frequently in the darbepoetin alfa arm than the placebo arm were fatigue (17.3% and 8.3%), pyrexia (9.2% and 2.1%), headache (7.1% and 2.1%), and myalgia (5.1% and 0%).

During the 48-week double-blind period, 7.9% (n=3) of patients formerly in the placebo arm and 3.4% (n=3) of patients formerly in the darbepoetin alfa arm had AEs that led to treatment discontinuation.