Procrit (Epoetin Alfa) - Description and Clinical Pharmacology

DESCRIPTION

PROCRIT (epoetin alfa) is a 165-amino acid erythropoiesis-stimulating glycoprotein manufactured by recombinant DNA technology. It has a molecular weight of approximately 30,400 daltons and is produced by mammalian cells into which the human erythropoietin gene has been introduced. The product contains the identical amino acid sequence of isolated natural erythropoietin.

PROCRIT is formulated as a sterile, colorless liquid in vials in multiple formulations. Single-dose vials, formulated with an isotonic sodium chloride/sodium citrate-buffered solution, are supplied in multiple strengths. Each 1 mL vial contains 2000, 3000, 4000, or 10,000 Units of epoetin alfa, Albumin (Human) (2.5 mg), citric acid (0.06 mg), sodium chloride (5.9 mg), and sodium citrate (5.8 mg) in Water for Injection, USP (pH 6.9 ± 0.3). Single-dose 1 mL vials formulated with an isotonic sodium chloride/sodium phosphate buffer contain 40,000 Units of epoetin alfa albumin (human) (2.5 mg),citric acid (0.0068 mg), sodium chloride (5.8 mg), sodium citrate (0.7 mg), sodium phosphate dibasic anhydrate (1.8 mg), and sodium phosphate monobasic monohydrate (1.2 mg) in Water for Injection, USP (pH 6.9 ± 0.3). Multidose, 2 mL vials contain 10,000 Units epoetin alfa, albumin (human) (2.5 mg), benzyl alcohol (1%), sodium chloride (8.2 mg), and sodium citrate (1.3 mg) per 1 mL Water for Injection, USP (pH 6.1 ± 0.3). Multidose 1 mL vials contain 20,000 Units epoetin alfa, albumin (human) (2.5 mg), benzyl alcohol (1%), sodium chloride (8.2 mg), citric acid (0.11 mg), and sodium citrate (1.3 mg), per 1 mL in Water for Injection, USP (pH 6.1 ± 0.3).

CLINICAL PHARMACOLOGY

Mechanism of Action

PROCRIT stimulates erythropoiesis by the same mechanism as endogenous erythropoietin.

Pharmacodynamics

PROCRIT increases the reticulocyte count within 10 days of initiation, followed by increases in the RBC count, hemoglobin, and hematocrit, usually within 2 to 6 weeks. The rate of hemoglobin increase varies among patients and is dependent upon the dose of PROCRIT administered. For correction of anemia in hemodialysis patients, a greater biologic response is not observed at doses exceeding 300 Units/kg 3 times weekly.

Pharmacokinetics

In adult and pediatric patients with CKD, the elimination half-life (t_1/2) of plasma erythropoietin after intravenous administration of PROCRIT ranged from 4 to 13 hours. After subcutaneous administration, Cmax was achieved within 5 to 24 hours. The t_1/2 in adult patients with serum creatinine greater than 3 mg/dL was similar between those not on dialysis and those maintained on dialysis. The pharmacokinetic data indicate no apparent difference in PROCRIT t_1/2 among adult patients above or below 65 years of age.

A pharmacokinetic study comparing 150 Units/kg subcutaneous 3 times weekly to 40,000 Units subcutaneous weekly dosing regimen was conducted for 4 weeks in healthy subjects (n = 12) and for 6 weeks in anemic cancer patients (n = 32) receiving cyclic chemotherapy. There was no accumulation of serum erythropoietin after the 2 dosing regimens during the study period. The 40,000 Units weekly regimen had a higher C_max (3- to 7-fold), longer T_max (2- to 3-fold), higher AUC_{0–168 h} (2- to 3-fold) of erythropoietin and lower clearance (CL) (50%) than the 150 Units/kg 3 times weekly regimen. In anemic cancer patients, the average t_1/2 was similar (40 hours with range of 16 to 67 hours) after both dosing regimens. After the 150 Units/kg 3 times weekly dosing, the values of T_max and CL were similar (13.3 ± 12.4 vs. 14.2 ± 6.7 hours, and 20.2 ± 15.9 vs. 23.6 ± 9.5 mL/hr/kg) between week 1 when patients were receiving chemotherapy (n = 14) and week 3 when patients were not receiving chemotherapy (n = 4). Differences were observed after the 40,000 Units weekly dosing with longer T_max (38 ± 18 hours) and lower CL (9.2 ± 4.7 mL/hr/kg) during week 1 when patients were receiving chemotherapy (n = 18) compared with those (22 ± 4.5 hours, 13.9 ± 7.6 mL/hr/kg, respectively) during week 3 when patients were not receiving chemotherapy (n = 7).

The pharmacokinetic profile of PROCRIT in children and adolescents appeared similar to that of adults.

The pharmacokinetics of PROCRIT has not been studied in patients with HIV infection.

NONCLINICAL TOXICOLOGY

Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenicity

The carcinogenic potential of PROCRIT has not been evaluated.

Mutagenicity

PROCRIT was not mutagenic or clastogenic under the conditions tested: PROCRIT was negative in the in vitro bacterial reverse mutation assay (Ames test), in the in vitro mammalian cell gene mutation assay (the hypoxanthine-guanine phosphoribosyl transferase [HGPRT] locus), in an in vitro chromosomal aberration assay in mammalian cells, and in the in vivo mouse micronucleus assay.

Impairment of Fertility

When administered intravenously to male and female rats prior to and during mating, and to females through the beginning of implantation (up to gestational day 7; dosing stopped prior to the beginning of organogenesis), doses of 100 and 500 Units/kg/day of PROCRIT caused slight increases in pre-implantation loss, post-implantation loss and decreases in the incidence of live fetuses. It is not clear whether these effects reflect a drug effect on the uterine environment or on the conceptus. This animal dose level of 100 Units/kg/day approximates the clinical recommended starting dose, depending on the patient's treatment indication, but may be lower than the clinical dose in patients whose doses have been adjusted.

Reproductive and Developmental Toxicology

When pregnant rats were administered intravenous PROCRIT, 500 Units/kg/day, after the period of organogenesis (from day 17 of gestation through day 21 of lactation), their pups exhibited decreased number of caudal vertebrae, decreased body weight gain, and delayed appearance of abdominal hair, eyelid opening, and ossification. This animal dose level of 500 Units/kg/day is approximately 5-fold higher than the clinical recommended starting dose, depending on the patient's treatment indication.

When PROCRIT was administered intravenously during the period of organogenesis to pregnant rats (gestational days 7 to 17) and pregnant rabbits (gestational days 6 to 18), no evidence of teratogenic outcome was observed at the doses tested, up to 500 Units/kg/day. The offspring (F1 generation) of the treated rats were observed postnatally; rats from the F1 generation reached maturity and were mated; no PROCRIT-related effects were apparent for their offspring (F2 generation fetuses).

CLINICAL STUDIES

Patients With Chronic Kidney Disease

Adult Patients on Dialysis

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

In clinical studies of CKD patients on dialysis, PROCRIT increased hemoglobin levels and decreased the need for RBC transfusion. Overall, more than 95% of patients were RBC transfusion-independent after receiving PROCRIT for 3 months. In clinical studies at starting doses of 50 to 150 Units/kg 3 times weekly, adult patients responded with an average rate of hemoglobin rise as presented in Table 8.

Table 8. Average Rate of Hemoglobin Rise in 2 Weeks

Starting Dose (3 Times Weekly Intravenously)	Hemoglobin Increase in 2 Weeks
50 Units/kg	0.5 g/dL
100 Units/kg	0.8 g/dL
150 Units/kg	1.2 g/dL

The safety and efficacy of PROCRIT were evaluated in 13 clinical studies involving intravenous administration to a total of 1010 anemic patients on dialysis. Overall, more than 90% of the patients treated with PROCRIT experienced improvement in hemoglobin concentrations. In the 3 largest of these clinical studies, the median maintenance dose necessary to maintain the hemoglobin between 10 to 12 g/dL was approximately 75 Units/kg 3 times weekly. More than 95% of patients were able to avoid RBC transfusions. In the largest US multicenter study, approximately 65% of the patients received doses of 100 Units/kg 3 times weekly or less to maintain their hemoglobin at approximately 11.7 g/dL. Almost 10% of patients received a dose of 25 Units/kg or less, and approximately 10% received a dose of more than 200 Units/kg 3 times weekly to maintain their hemoglobin at this level.

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).

Other ESA trials

In a 26-week, double-blind, placebo-controlled study, 118 patients on dialysis with an average hemoglobin of approximately 7 g/dL were randomized to either PROCRIT or placebo. By the end of the study, average hemoglobin increased to approximately 11 g/dL in the PROCRIT-treated patients and remained unchanged in patients receiving placebo. PROCRIT-treated patients experienced improvements in exercise tolerance and patient-reported physical functioning at month 2 that were maintained throughout the study.

A multicenter, unit-dose study was also conducted in 119 patients receiving peritoneal dialysis who self-administered PROCRIT subcutaneously. Patients responded to PROCRIT administered subcutaneously in a manner similar to patients receiving intravenous administration.

Pediatric Patients on Dialysis

The safety and efficacy of PROCRIT were studied in a placebo-controlled, randomized study of 113 children with anemia (hemoglobin ≤ 9 g/dL) undergoing peritoneal dialysis or hemodialysis. The initial dose of PROCRIT was 50 Units/kg intravenously or subcutaneously 3 times weekly. The dose of study drug was titrated to achieve either a hemoglobin of 10 to 12 g/dL or an absolute increase in hemoglobin of 2 g/dL over baseline.

At the end of the initial 12 weeks, a statistically significant rise in mean hemoglobin (3.1 g/dL vs. 0.3 g/dL) was observed only in the PROCRIT arm. The proportion of children achieving a hemoglobin of 10 g/dL, or an increase in hemoglobin of 2 g/dL over baseline, at any time during the first 12 weeks was higher in the PROCRIT arm (96% vs. 58%). Within 12 weeks of initiating PROCRIT therapy, 92.3% of the pediatric patients were RBC transfusion independent as compared to 65.4% who received placebo. Among patients who received 36 weeks of PROCRIT, hemodialysis patients received a higher median maintenance dose [167 Units/kg/week (n = 28) vs. 76 Units/kg/week (n = 36)] and took longer to achieve a hemoglobin of 10 to 12 g/dL (median time to response 69 days vs. 32 days) than patients undergoing peritoneal dialysis.

Adult Patients With CKD Not Requiring Dialysis

Four clinical studies were conducted in patients with CKD not on dialysis involving 181 patients treated with PROCRIT. These patients responded to PROCRIT therapy in a manner similar to that observed in patients on dialysis. Patients with CKD not on dialysis demonstrated a dose-dependent and sustained increase in hemoglobin when PROCRIT was administered by either an intravenous or subcutaneous route, with similar rates of rise of hemoglobin when PROCRIT was administered by either route.

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 an ESA to target a hemoglobin of 13 g/dL compared to the control arm in which an ESA 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 epoetin alfa 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 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].

Zidovudine-treated Patients With HIV Infection

The safety and efficacy of PROCRIT were evaluated in 4 placebo-controlled studies enrolling 297 anemic patients (hemoglobin < 10 g/dL) with HIV infection receiving concomitant therapy with zidovudine. In the subgroup of patients (89/125 PROCRIT and 88/130 placebo) with pre-study endogenous serum erythropoietin levels ≤ 500 mUnits/mL, PROCRIT reduced the mean cumulative number of units of blood transfused per patient by approximately 40% as compared to the placebo group. Among those patients who required RBC transfusions at baseline, 43% of patients treated with PROCRIT versus 18% of placebo-treated patients were RBC transfusion-independent during the second and third months of therapy. PROCRIT therapy also resulted in significant increases in hemoglobin in comparison to placebo. When examining the results according to the weekly dose of zidovudine received during month 3 of therapy, there was a statistically significant reduction (p < 0.003) in RBC transfusion requirements in patients treated with PROCRIT (n = 51) compared to placebo-treated patients (n = 54) whose mean weekly zidovudine dose was ≤ 4200 mg/week.

Approximately 17% of the patients with endogenous serum erythropoietin levels ≤ 500 mUnits/mL receiving PROCRIT in doses from 100 to 200 Units/kg 3 times weekly achieved a hemoglobin of 12.7 g/dL without administration of RBC transfusions or significant reduction in zidovudine dose. In the subgroup of patients whose pre-study endogenous serum erythropoietin levels were > 500 mUnits/mL, PROCRIT therapy did not reduce RBC transfusion requirements or increase hemoglobin compared to the corresponding responses in placebo-treated patients.

Cancer Patients on Chemotherapy

The safety and effectiveness of PROCRIT was assessed in two multicenter, randomized (1:1), placebo-controlled, double-blind studies (Study C1 and Study C2) and a pooled analysis of six additional randomized (1:1), multicenter, placebo-controlled, double-blind studies. All studies were conducted in patients with anemia due to concomitantly administered cancer chemotherapy. Study C1 enrolled 344 adult patients, Study C2 enrolled 222 pediatric patients, and the pooled analysis contained 131 patients randomized to epoetin alfa or placebo. In Studies C1 and C2, efficacy was demonstrated by a reduction in the proportion of patients who received an RBC transfusion, from week 5 through end of the study, with the last-known RBC transfusion status carried forward for patients who discontinued treatment. In the pooled analysis, efficacy was demonstrated by a reduction in the proportion of patients who received an RBC transfusion from week 5 through end of the study in the subset of patients who were remaining on therapy for 6 or more weeks.

Study C1

Study C1 was conducted in anemic patients (hemoglobin < 11.5 g/dL for males; < 10.5 g/dL for females) with non-myeloid malignancies receiving myelosuppressive chemotherapy. Randomization was stratified by type of malignancy (lung vs. breast vs. other), concurrent radiation therapy planned (yes or no), and baseline hemoglobin (< 9 g/dL vs. ≥ 9 g/dL); patients were randomized to epoetin alfa 40,000 Units (n = 174) or placebo (n = 170) as a weekly subcutaneous injection commencing on the first day of the chemotherapy cycle.

Ninety-one percent of patients were white, 44% were male, and the median age of patients was 66 years (range: 20 to 88 years). The proportion of patients withdrawn from the study prior to week 5 was less than 10% for placebo-treated or epoetin-treated patients. Per protocol, the last available hemoglobin values from patients who dropped out were included in the efficacy analyses. Efficacy results are shown in Table 9.

Table 9. Study C1: Proportion of Patients Transfused

	Week 5 Through Week 16 or End of Study
Chemotherapy Regimen	PROCRIT (n = 174)	Placebo (n = 170)
All Regimens	14% (25/174)	28% (48/170)
Regimens without cisplatin	14% (21/148)	26% (35/137)
Regimens containing cisplatin	15% (4/26)	39% (13/33)

Study C2

Study C2 was conducted in 222 anemic patients, ages 5 to 18, receiving chemotherapy for the treatment of various childhood malignancies. Randomization was stratified by cancer type (solid tumors, Hodgkin's disease, acute lymphocytic leukemia, vs. non-Hodgkin's lymphoma); patients were randomized to receive epoetin alfa at 600 Units/kg maximum 40,000 Units (n = 111) or placebo (n = 111) as a weekly intravenous injection.

Sixty-nine percent of patients were white, 55% were male, and the median age of patients was 12 years (range: 5 to 18 years). Two (2%) of placebo-treated patients and 3 (3%) of epoetin alfa-treated patients dropped out of the study prior to week 5. There were fewer RBC transfusions from week 5 through the end-of-study in epoetin-alfa treated patients [51% (57/111)] compared to placebo-treated patients [69% (77/111)]. There was no evidence of an improvement in health-related quality of life, including no evidence of an effect on fatigue, energy, or strength in patients receiving PROCRIT as compared to those receiving placebo.

Pooled Analysis (Three Times Per Week Dosing)

The results of 6 studies of similar design and that randomized 131 patients to epoetin alfa or placebo were pooled to assess the safety and effectiveness of epoetin alfa. Patients were randomized to receive epoetin alfa at 150 Units/kg (n = 63) or placebo (n = 68), subcutaneously three times per week for 12 weeks in each study. Across all studies, 72 patients were treated with concomitant non cisplatin-containing chemotherapy regimens and 59 patients were treated with concomitant cisplatin-containing chemotherapy regimens. Twelve patients (19%) in the epoetin alfa arm and 10 patients (15%) in the placebo-arm dropped out prior to week 6 and are excluded from efficacy analyses.

Table 10: Proportion of Patients Transfused in the Pooled Analysis for Three Times Per Week Dosing

	Week 5 Through Week 12 or End of Study
Chemotherapy Regimen	PROCRIT	Placebo
All Regimens	22% (11/51)	43% (25/58)
Regimens without cisplatin	21% (6/29)	33% (11/33)
Regimens containing cisplatin	23% (5/22)	56% (14/25)

Surgery Patients

The safety and efficacy of PROCRIT were evaluated in a placebo-controlled, double-blind study (S1) enrolling 316 patients scheduled for major, elective orthopedic hip or knee surgery who were expected to require ≥ 2 units of blood and who were not able or willing to participate in an autologous blood donation program. Patients were stratified into 1 of 3 groups based on their pretreatment hemoglobin [≤ 10 g/dL (n = 2), > 10 to ≤ 13 g/dL (n = 96), and > 13 to ≤ 15 g/dL (n = 218)] and then randomly assigned to receive 300 Units/kg PROCRIT, 100 Units/kg PROCRIT, or placebo by subcutaneous injection for 10 days before surgery, on the day of surgery, and for 4 days after surgery. All patients received oral iron and a low-dose, postoperative warfarin regimen.

Treatment with PROCRIT 300 Units/kg significantly (p = 0.024) reduced the risk of allogeneic RBC transfusion in patients with a pretreatment hemoglobin of > 10 to ≤ 13 g/dL; 5/31 (16%) of patients treated with PROCRIT 300 Units/kg, 6/26 (23%) of patients treated with PROCRIT 100 Units/kg, and 13/29 (45%) of placebo-treated patients were transfused. There was no significant difference in the number of patients transfused between PROCRIT (9% 300 Units/kg, 6% 100 Units/kg) and placebo (13%) in the > 13 to ≤ 15 g/dL hemoglobin stratum. There were too few patients in the ≤ 10 g/dL group to determine if PROCRIT is useful in this hemoglobin strata. In the > 10 to ≤ 13 g/dL pretreatment stratum, the mean number of units transfused per PROCRIT-treated patient (0.45 units blood for 300 Units/kg, 0.42 units blood for 100 Units/kg) was less than the mean transfused per placebo-treated patient (1.14 units) (overall p = 0.028). In addition, mean hemoglobin, hematocrit, and reticulocyte counts increased significantly during the presurgery period in patients treated with PROCRIT.

PROCRIT was also evaluated in an open-label, parallel-group study (S2) enrolling 145 patients with a pretreatment hemoglobin level of ≥ 10 to ≤ 13 g/dL who were scheduled for major orthopedic hip or knee surgery and who were not participating in an autologous program. Patients were randomly assigned to receive 1 of 2 subcutaneous dosing regimens of PROCRIT (600 Units/kg once weekly for 3 weeks prior to surgery and on the day of surgery, or 300 Units/kg once daily for 10 days prior to surgery, on the day of surgery, and for 4 days after surgery). All patients received oral iron and appropriate pharmacologic anticoagulation therapy.

From pretreatment to presurgery, the mean increase in hemoglobin in the 600 Units/kg weekly group (1.44 g/dL) was greater than that observed in the 300 Units/kg daily group. The mean increase in absolute reticulocyte count was smaller in the weekly group (0.11 × 10⁶/mm³) compared to the daily group (0.17 × 10⁶/mm³). Mean hemoglobin levels were similar for the 2 treatment groups throughout the postsurgical period.

The erythropoietic response observed in both treatment groups resulted in similar RBC transfusion rates [11/69 (16%) in the 600 Units/kg weekly group and 14/71 (20%) in the 300 Units/kg daily group]. The mean number of units transfused per patient was approximately 0.3 units in both treatment groups.