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Aranesp (Erythropoiesis Stimulating Protein) - Description and Clinical Pharmacology

 
 



DESCRIPTION

Aranesp (darbepoetin alfa) is an erythropoiesis-stimulating protein that is produced in Chinese hamster ovary (CHO) cells by recombinant DNA technology. Aranesp is a 165-amino acid protein that differs from recombinant human erythropoietin in containing 5 N-linked oligosaccharide chains, whereas recombinant human erythropoietin contains 3 chains. The 2 additional N-glycosylation sites result from amino acid substitutions in the erythropoietin peptide backbone. The approximate molecular weight of darbepoetin alfa is 37,000 daltons.

Aranesp is formulated as a sterile, colorless, preservative-free solution containing polysorbate for intravenous or subcutaneous administration. Each 1 mL contains polysorbate 80 (0.05 mg), sodium chloride (8.18 mg), sodium phosphate dibasic anhydrous (0.66 mg), and sodium phosphate monobasic monohydrate (2.12 mg) in Water for Injection, USP (pH 6.2 ± 0.2).

CLINICAL PHARMACOLOGY

Mechanism of Action

Aranesp stimulates erythropoiesis by the same mechanism as endogenous erythropoietin.

Pharmacodynamics

Increased hemoglobin levels are not generally observed until 2 to 6 weeks after initiating treatment with Aranesp.

Pharmacokinetics


Adult Patients with CKD


The pharmacokinetics of Aranesp were studied in patients with CKD receiving or not receiving dialysis and cancer patients receiving chemotherapy.


Following intravenous administration of Aranesp to patients with CKD receiving dialysis, Aranesp serum concentration-time profiles were biphasic, with a distribution half-life of approximately 1.4 hours and a mean terminal half-life (t1/2) of 21 hours. The t1/2 of Aranesp was approximately 3-fold longer than that of epoetin alfa when administered intravenously.


Following subcutaneous administration of Aranesp to patients with CKD (receiving or not receiving dialysis), absorption was slow and Cmax occurred at 48 hours (range: 12 to 72 hours). In patients with CKD receiving dialysis, the average t1/2 was 46 hours (range: 12 to 89 hours), and in patients with CKD not receiving dialysis, the average t1/2 was 70 hours (range: 35 to 139 hours). Aranesp apparent clearance was approximately 1.4 times faster on average in patients receiving dialysis compared to patients not receiving dialysis. The bioavailability of Aranesp in patients with CKD receiving dialysis after subcutaneous administration was 37% (range: 30% to 50%).

Pediatric Patients with CKD


Aranesp pharmacokinetics was studied in 12 pediatric patients (age 3 to 16 years) with CKD receiving or not receiving dialysis. Following a single intravenous or subcutaneous Aranesp dose, Cmax and t1/2 were similar to those obtained in adult patients with CKD on dialysis. Following a single subcutaneous dose, the average bioavailability was 54% (range: 32% to 70%), which was higher than that obtained in adult patients with CKD on dialysis.

Adult Cancer Patients


Following the first subcutaneous dose of 6.75 mcg/kg (equivalent to 500 mcg for a 74-kg patient) in patients with cancer, the mean t1/2 was 74 hours (range: 24 to 144 hours) and Cmax was observed at 71 hours (range: 28 to 120 hours). When administered on a once every 3 week schedule, 48-hour postdose Aranesp levels after the fourth dose were similar to those after the first dose.


Over the dose range of 0.45 to 4.5 mcg/kg Aranesp administered intravenously or subcutaneously on a once weekly schedule and 4.5 to 15 mcg/kg administered subcutaneously on a once every 3 week schedule, systemic exposure was approximately proportional to dose. No evidence of accumulation was observed beyond an expected less than 2-fold increase in blood levels when compared to the initial dose.

NONCLINICAL TOXICOLOGY

Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenicity


The carcinogenic potential of Aranesp has not been evaluated in long-term animal studies. In toxicity studies of approximately 6 months duration in rats and dogs, no tumorigenic or unexpected mitogenic responses were observed in any tissue type.

Mutagenicity


Aranesp was not mutagenic or clastogenic under the conditions tested. Aranesp was negative in the in vitro bacterial reverse mutation assay, the in vitro mammalian cell gene mutation assay (using CHO cells), and in the in vivo mouse erythrocyte micronucleus assay.

Impairment of Fertility


Aranesp increased the incidence of post-implantation losses in rats. Male and female rats received intravenous doses prior to and during mating; then females were treated 3 times weekly during the first trimester of gestation (gestation days 1, 3, 5, and 7). No effect on reproductive performance, fertility, or sperm assessment parameters were detected at any of the doses evaluated (up to 10 mcg/kg, administered 3 times weekly). The dose of 10 mcg/kg is more than 10-fold higher than the clinical recommended starting dose. An increase in post-implantation fetal loss was seen at doses equal to or greater than 0.5 mcg/kg, administered 3 times weekly. The dose of 0.5 mcg/kg is approximately equivalent to the clinical recommended starting dose. Signs of exaggerated pharmacology were not observed in the mother receiving 0.5 mcg/kg or less, but were observed at 2.5 mcg/kg and higher.

Reproductive and Developmental Toxicology

When Aranesp was administered intravenously during organogenesis to pregnant rats (gestational days 6 to 15) and rabbits (gestational days 6 to 18), no evidence of direct embryotoxic, fetotoxic, or teratogenic outcomes were observed at the doses tested, up to 20 mcg/kg/day. This animal dose level of 20 mcg/kg/day is approximately 20-fold higher than the clinical recommended starting dose, depending on the patient’s treatment indication. The only adverse effect observed was a slight reduction in fetal weight, which occurred only at doses causing exaggerated pharmacological effects in both the rat and rabbit dams (1 mcg/kg/day and higher). No deleterious effects on uterine implantation were seen in either species.


No significant placental transfer of Aranesp was observed in rats; placental transfer was not evaluated in rabbits.


In a peri/postnatal development study, pregnant female rats were treated intravenously with Aranesp day 6 of gestation through day 23 of lactation at 2.5 mcg/kg and higher every other day. Pups of treated mothers had decreased fetal body weights, which correlated with slight increases in the incidences of fetal death, as well as delayed eye opening and delayed preputial separation. The offspring (F1 generation) of the treated rats were observed postnatally; rats from the F1 generation reached maturity and were mated; no Aranesp-related effects were apparent for their offspring (F2 generation fetuses).

CLINICAL STUDIES

Clinical studies in the nephrology and chemotherapy-induced anemia clinical programs are designated with the prefixes “N” and “C”, respectively.

Patients With Chronic Kidney Disease


Patients with chronic kidney disease on dialysis: ESA effects on rates of transfusion

In early clinical studies conducted in CKD patients on dialysis, ESAs have been shown to reduce the use of RBC transfusions. These studies enrolled patients with mean baseline hemoglobin levels of approximately 7.5 g/dL and ESAs were generally titrated to achieve a hemoglobin level of approximately 12 g/dL. Fewer transfusions were given during the ESA treatment period when compared to a pre-treatment interval.


In the Normal Hematocrit Study, the yearly transfusion rate was 51.5% in the lower hemoglobin group (10 g/dL) and 32.4% in the higher hemoglobin group (14 g/dL).


Patients with chronic kidney disease not on dialysis: ESA effects on rates of transfusion


In TREAT, a randomized, double-blind trial of 4038 patients with CKD and type 2 diabetes not on dialysis, a post-hoc analysis showed that the proportion of patients receiving RBC transfusions was lower in patients administered Aranesp to target a hemoglobin of 13 g/dL compared to the control arm in which Aranesp was administered intermittently if hemoglobin concentration decreased to less than 9 g/dL (15% versus 25%, respectively). In CHOIR, a randomized open-label study of 1432 patients with CKD not on dialysis, use of an ESA to target a higher (13.5 g/dL) versus lower (11.3 g/dL) hemoglobin goal did not reduce the use of RBC transfusions. In each trial, no benefits occurred for the cardiovascular or end-stage renal disease outcomes. In each trial, the potential benefit of ESA therapy was offset by worse cardiovascular safety outcomes resulting in an unfavorable benefit-risk profile [see Warnings and Precautions ].


ESA Effects on quality of life


Aranesp use has not been demonstrated in controlled clinical trials to improve quality of life, fatigue, or patient well-being.


ESA Effects on rates of death and other serious cardiac adverse events


Three randomized outcome trials (Normal Hematocrit Study [NHS], Correction of Anemia with Epoetin Alfa in Chronic Kidney Disease [CHOIR], and Trial of Darbepoetin Alfa in Type 2 Diabetes and CKD [TREAT]) have been conducted in patients with CKD using Epogen/PROCRIT/Aranesp to target higher vs. lower hemoglobin levels. Though these trials were designed to establish a cardiovascular or renal benefit of targeting higher hemoglobin levels, in all 3 studies, patients randomized to the higher hemoglobin target experienced worse cardiovascular outcomes and showed no reduction in progression to ESRD. In each trial, the potential benefit of ESA therapy was offset by worse cardiovascular safety outcomes resulting in an unfavorable benefit-risk profile [see Warnings and Precautions ].


Other ESA trials


Two studies evaluated the safety and efficacy of the de novo use of Aranesp for the correction of anemia in adult patients with CKD, and 3 studies (2 in adults and 1 in pediatric patients) assessed the ability of Aranesp to maintain hemoglobin concentrations in patients with CKD who had been receiving other recombinant erythropoietins.


De Novo Use of Aranesp

Once Weekly Aranesp Starting Dose

In 2 randomized, open-label studies, Aranesp or epoetin alfa was administered for the correction of anemia in patients with CKD who had not been receiving prior treatment with exogenous erythropoietin. Study N1 evaluated CKD patients receiving dialysis; Study N2 evaluated patients not requiring dialysis. In both studies, the starting dose of Aranesp was 0.45 mcg/kg administered once weekly. The starting dose of epoetin alfa was 50 Units/kg 3 times weekly in Study N1 and 50 Units/kg twice weekly in Study N2. When necessary, dosage adjustments were instituted to maintain hemoglobin in the study target range of 11 to 13 g/dL. (Note: The recommended hemoglobin target range is lower than the target range of these studies [see Dosage and Administration].) The primary efficacy endpoint was the proportion of patients who experienced at least a 1 g/dL increase in hemoglobin concentration to a level of at least 11 g/dL by 20 weeks (Study N1) or 24 weeks (Study N2). The studies were designed to assess the safety and effectiveness of Aranesp but not to support conclusions regarding comparisons between the 2 products.


In Study N1, the primary efficacy endpoint was achieved by 72% (95% CI: 62%, 81%) of the 90 patients treated with Aranesp and 84% (95% CI: 66%, 95%) of the 31 patients treated with epoetin alfa. The mean increase in hemoglobin over the initial 4 weeks of Aranesp treatment was 1.1 g/dL (95% CI: 0.82 g/dL, 1.37 g/dL).


In Study N2, the primary efficacy endpoint was achieved by 93% (95% CI: 87%, 97%) of the 129 patients treated with Aranesp and 92% (95% CI: 78%, 98%) of the 37 patients treated with epoetin alfa. The mean increase in hemoglobin from baseline through the initial 4 weeks of Aranesp treatment was 1.38 g/dL (95% CI: 1.21 g/dL, 1.55 g/dL).

Once Every 2 Week Aranesp Starting Dose


In 2 single-arm studies (N3 and N4), Aranesp was administered for the correction of anemia in CKD patients not receiving dialysis. In both studies, the starting dose of Aranesp was 0.75 mcg/kg administered once every 2 weeks.


In Study N3 (study duration of 18 weeks), the hemoglobin goal (hemoglobin concentration ≥ 11 g/dL) was achieved by 92% (95% CI: 86%, 96%) of the 128 patients treated with Aranesp.


In Study N4 (study duration of 24 weeks), the hemoglobin goal (hemoglobin concentration of 11 to 13 g/dL) was achieved by 85% (95% CI: 77%, 93%) of the 75 patients treated with Aranesp.

Conversion from Other Recombinant Erythropoietins


Two studies of adults (N5 and N6) and 1 study in pediatric patients (N7) were conducted in patients who had been receiving other recombinant erythropoietins for treatment of the anemia due to CKD. The studies compared the abilities of Aranesp and other erythropoietins to maintain hemoglobin concentrations within a study target range of 9 to 13 g/dL in adults and 10 to 12.5 g/dL in pediatric patients. (Note: The recommended hemoglobin target is lower than the target range of these studies [see Dosage and Administration ( 2.2 )].) Patients who had been receiving stable doses of other recombinant erythropoietins were randomized to Aranesp or continued with their prior erythropoietin at the previous dose and schedule. For patients randomized to Aranesp, the initial weekly dose was determined on the basis of the previous total weekly dose of recombinant erythropoietin.

Adult Patients


Study N5  was a double-blind study in which 169 hemodialysis patients were randomized to treatment with Aranesp and 338 patients continued on epoetin alfa. Study N6 was an open-label study in which 347 patients were randomized to treatment with Aranesp and 175 patients were randomized to continue on epoetin alfa or epoetin beta. Of the patients randomized to Aranesp, 92% were receiving hemodialysis and 8% were receiving peritoneal dialysis.


In Study N5, a median weekly dose of 0.53 mcg/kg Aranesp (25th, 75th percentiles: 0.30, 0.93 mcg/kg) was required to maintain hemoglobin in the study target range. In Study N6, a median weekly dose of 0.41 mcg/kg Aranesp (25th, 75th percentiles: 0.26, 0.65 mcg/kg) was required to maintain hemoglobin in the study target range.

Pediatric Patients


Study N7 was an open-label, randomized study conducted in the United States in pediatric patients from 1 to 18 years of age with CKD receiving or not receiving dialysis. Eighty-one patients with hemoglobin concentrations that were stable on epoetin alfa received darbepoetin alfa (subcutaneously or intravenously), and 42 patients continued to receive epoetin alfa at the current dose, schedule, and route of administration. Patients received darbepoetin alfa once weekly if previously receiving epoetin alfa 2 or 3 times weekly or once every other week if previously receiving epoetin alfa weekly. A median weekly dose of 0.41 mcg/kg darbepoetin alfa (25th, 75th percentiles: 0.25, 0.82 mcg/kg) was required to maintain hemoglobin in the study target range.

Cancer Patients Receiving Chemotherapy

The safety and efficacy of Aranesp was assessed in two multicenter, randomized studies in patients with anemia due to the effect of concomitantly administered cancer chemotherapy. Study C1 was a randomized (1:1), placebo-controlled, double-blind, multinational study conducted in 314 patients where Aranesp was administered weekly. Study C2 was a randomized (1:1), double-blind, double-dummy, active-controlled, multinational study conducted in 705 patients where Aranesp was administered either every week or every 3 weeks. Efficacy was demonstrated by a statistically significant reduction in the proportion of patients receiving RBC transfusions among patients who were on study therapy for more than 28 days.

Study C1


Study C1 was conducted in anemic patients (hemoglobin ≤ 11 g/dL) with non-small cell lung cancer or small cell lung cancer who were scheduled to receive at least 12 weeks of a platinum-containing chemotherapy regimen. Randomization was stratified by tumor type and region (Australia vs. Canada vs. Europe). Patients received Aranesp 2.25 mcg/kg or placebo as a weekly subcutaneous injection commencing on the first day of the chemotherapy cycle. Efficacy was determined by a reduction in the proportion of patients who received RBC transfusions between week 5 (day 29) and end of treatment period (12 weeks) in the subset of 297 randomized patients (148 Aranesp and 149 placebo) who were on-study at the beginning of study week 5. All 297 patients were white, 72% were male, 71% had non-small cell histology, and the median age was 62 years (range: 36 to 80). A significantly lower proportion of patients in the Aranesp arm received RBC transfusions during week 5 to the end of treatment compared to patients in the placebo arm (crude percentages: 26% vs. 50%; p < 0.001, based on a comparison of the difference in Kaplan-Meier proportions using the Cochran-Mantel-Haenszel strata-adjusted Chi-square test).

Study C2


Study C2 was conducted in anemic patients (hemoglobin < 11 g/dL) with non-myeloid malignancies receiving chemotherapy. Randomization was stratified by region (Western vs. Central/Eastern Europe), tumor type (lung and gynecological vs. others), and baseline hemoglobin (< 10 vs. ≥ 10 g/dL); all patients received double-dummy placebo and either Aranesp  500 mcg every 3 weeks or Aranesp 2.25 mcg/kg weekly subcutaneous injections for 15 weeks. Only 1 patient was non-white, 55% were female, and the median age was 60 years (range: 20 to 86). One hundred seven patients (16%) had lung or gynecological cancer while 565 (84%) had other tumor types. In both treatment schedules, the dose was reduced by 40% of the previous dose if hemoglobin level increased by more than 1 g/dL in a 14-day period.


Efficacy was determined by a comparison of the proportion of patients who received at least 1 RBC transfusion between week 5 (day 29) and the end of treatment. Three hundred thirty-five patients in the every 3 week dosing arm and 337 patients in the weekly dosing arm remained on study through or beyond day 29 and were evaluable for efficacy. Two hundred thirty-eight patients (71%) in the every 3 week arm and 261 patients (77%) patients in the weekly arm required dose reductions. Twenty-three percent (95% CI: 18%, 28%) of patients in the every 3 week treatment schedule and 28% (95% CI: 24%, 34%) in the weekly schedule received at least 1 RBC transfusion. The observed difference in the RBC transfusion rates (every 3 week minus weekly) was -5.8% (95% CI: -12.4%, 0.8%).

Study C3


Lack of Efficacy in Improving Survival


Study C3 was conducted in patients required to have a hemoglobin concentration ≥ 9 g/dL and ≤ 13 g/dL with previously untreated extensive-stage small cell lung cancer (SCLC) receiving platinum and etoposide chemotherapy.  Randomization was stratified by region (Western Europe, Australia/North America, and rest of world), Eastern Cooperative Oncology Group (ECOG) performance status (0 or 1 vs. 2), and lactate dehydrogenase (below vs. above the upper limit of normal).  Patients were randomized to receive Aranesp  (n = 298) at a dose of 300 mcg once weekly for the first 4 weeks, followed by 300 mcg once every 3 weeks for the remainder of the treatment period or placebo (n = 298). 


This study was designed to detect a prolongation in overall survival (from a median of 9 months to a median of 12 months). For the final analysis, there was no evidence of improved survival (p=0.43, log-rank test).

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