CLINICAL PHARMACOLOGY
Mechanism Of Action
KGF is an endogenous protein in the fibroblast growth factor (FGF) family that binds to the KGF receptor. Binding of KGF to its receptor has been reported to result in proliferation, differentiation, and migration of epithelial cells. The KGF receptor, one of four receptors in the FGF family, has been reported to be present on epithelial cells in many tissues examined including the tongue, buccal mucosa, esophagus, stomach, intestine, salivary gland, lung, liver, pancreas, kidney, bladder, mammary gland, skin (hair follicles and sebaceous gland), and the lens of the eye. The KGF receptor has been reported to not be present on cells of the hematopoietic lineage. Endogenous KGF is produced by mesenchymal cells and is upregulated in response to epithelial tissue injury.
In mice and rats, Kepivance enhanced proliferation of epithelial cells (as measured by Ki67 immunohistochemical staining and BrDU uptake) and demonstrated an increase in tissue thickness of the tongue, buccal mucosa, and gastrointestinal tract. Kepivance has been studied in murine models of chemotherapy and radiation-induced gastrointestinal injury. In such models, administration of Kepivance prior to and/or after the cytotoxic insult improved survival and reduced weight loss compared to control animals.
Kepivance has been shown to enhance the growth of human epithelial tumor cell lines in vitro at concentrations ≥ 10 mcg/mL (> 15-fold higher than average therapeutic concentrations in humans). In nude mouse xenograft models, three consecutive daily treatments of Kepivance at doses of 1,500 and 4,000 mcg/kg (25-and 67-fold higher than the recommended human dose, respectively) repeated weekly for 4 to 6 weeks were associated with a dose-dependent increase in the growth rate of 1 of 7 KGF receptor-expressing human tumor cell lines.
Pharmacodynamics
Epithelial cell proliferation was assessed by Ki67 immunohistochemical staining in healthy subjects. A 3-fold or greater increase in Ki67 staining was observed in buccal biopsies from 3 of 6 healthy subjects given Kepivance at 40 mcg/kg/day intravenously for 3 days, when measured 24 hours after the third dose. Dose-dependent epithelial cell proliferation was observed in healthy subjects given single intravenous doses of 120 to 250 mcg/kg 48 hours post-dosing.
Pharmacokinetics
The pharmacokinetics of Kepivance were studied in healthy subjects and patients with hematologic malignancies. After single intravenous doses of 20 to 250 mcg/kg in healthy subjects and 60 mcg/kg in cancer patients, Kepivance concentrations declined over 95% in the first 30 minutes post-dose. A slight increase or plateau in concentration occurred at approximately 1 to 4 hours, followed by a terminal decline phase. Kepivance exhibited linear pharmacokinetics with extravascular distribution. In cancer patients compared with healthy subjects, after a 60 mcg/kg single dose of Kepivance the average total body clearance (CL) was 2-to 4-fold higher, and volume of distribution at steady state (Vss) was 2-fold higher. The elimination half-life was similar between healthy subjects and cancer patients (average 4.5 hours with a range of 3.3 to 5.7 hours). No accumulation of Kepivance occurred after 3 consecutive daily doses of 20 and 40 mcg/kg in healthy subjects or 60 mcg/kg in cancer patients. Age (1 to 16 years) did not affect the pharmacokinetics of palifermin over the dose range of 40 to 80 mcg/kg [see Use In Specific Populations].
Drug Interactions
Co-Administration With Heparin
The potential pharmacokinetic interaction between palifermin and heparin was evaluated in a single-dose study in 27 healthy subjects receiving palifermin (60 mcg/kg) co-administered with and without therapeutic levels of unfractionated heparin. This co-administration resulted in a 5-fold increase in palifermin AUC and an 80% decrease in the mean CL. There was no significant effect of palifermin on heparin activity with respect to activated partial thromboplastin time (aPTT). A second study was conducted in 31 evaluable healthy subjects receiving palifermin (40 mcg/kg/day for 3 days) co-administered with and without therapeutic levels of unfractionated heparin. In this study, coadministration of heparin and palifermin resulted in a 425% increase in palifermin AUC and a 76.5, 73.1, and 38.8% decrease in palifermin CL, volume of distribution, and half-life, respectively. These changes in palifermin PK did not have a noticeable effect on Ki67 expression in buccal biopsies, used as a marker of epithelial cell proliferation.
Pharmacokinetics In Specific Populations
Renal Impairment
Results from a pharmacokinetics study in 24 subjects with varying degrees of renal impairment demonstrated that renal impairment has little or no influence on Kepivance pharmacokinetics
Hepatic Impairment
The pharmacokinetic profile of patients with hepatic insufficiency has not been assessed.
Elderly
In a single-dose study, subjects received a 180-mcg/kg or 90-mcg/kg dose of palifermin administered by intravenous bolus injection. Subjects over the age of 65 (n=8) had an approximately 30% lower rate of CL on average than those 65 and younger (n=19). No dose adjustment is recommended for the geriatric population [see Use In Specific Populations].
Clinical Studies
Autologous Transplantation Preparative Regimens That Include Total Body Irradiation
The safety and efficacy of Kepivance in decreasing the incidence and duration of severe oral mucositis in patients with hematologic malignancies (NHL, Hodgkin’s disease, acute myeloid leukemia, acute lymphoblastic leukemia, chronic myeloid leukemia, chronic lymphocytic leukemia, or multiple myeloma) receiving myelotoxic therapy requiring hematopoietic stem cell support, were established in a randomized placebo-controlled clinical trial of 212 patients (Study 1) and a randomized, schedule-ranging, placebo-controlled clinical trial of 169 patients (Study 2).
In Study 1, patients received high-dose cytotoxic therapy consisting of fractionated total-body irradiation (TBI) (12 Gy total dose), high-dose etoposide (60 mg/kg), and high-dose cyclophosphamide (100 mg/kg) followed by hematopoietic stem cell support. Patients were randomized to receive either Kepivance (n = 106) or placebo (n = 106). Kepivance 60 mcg/kg was administered as a daily intravenous injection for 3 consecutive days prior to initiation of cytotoxic therapy and for 3 consecutive days following infusion of hematopoietic stem cells. The major efficacy outcome was the number of days during which patients experienced severe oral mucositis (Grade 3/4 on the WHO [World Health Organization] scale)1. Other analyses included the incidence, duration, and severity of oral mucositis and the use of opioid analgesia. There was no evidence of a delay in time to hematopoietic recovery in patients who received Kepivance as compared to patients who received placebo. The results of Study 1 are presented in Table 2 and Figure 1.
Table 2: Study 1 Efficacy Outcomes
Efficacy Variable | Kepivance (60 mcg/kg/day) (n = 106) | Placebo (n = 106) |
Median (25th, 75th percentile) Days of WHO Grade 3/4 Oral Mucositis* | 3 (0, 6) | 9 (6, 13) |
Incidence of WHO Grade 3/4 Oral Mucositis | 63% (67/106) | 98% (104/106) |
Median (25th, 75th percentile) Days of WHO Grade 3/4 Oral Mucositis in Affected Patients | 6 (3, 8) (n = 67) | 9 (6, 13) (n = 104) |
Incidence of WHO Grade 4 Oral Mucositis | 20% | 62% |
Median (25th, 75th percentile) Cumulative Opiod Dose (morphine mg equivalents) | 212 (3, 558) | 535 (269, 1429) |
* P < 0.001 compared to placebo, using Generalized Cochran-Mantel-Haenszel (CMH) test stratified for study center. |
Figure 1: Study 1 Incidence of Oral Mucositis by Maximum Grade WHO Oral Mucositis Scale
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Study 2 was a randomized, multi-center, placebo-controlled trial comparing varying schedules of Kepivance. All patients received high-dose cytotoxic therapy consisting of fractionated TBI (12cGy total dose), high-dose etoposide (60 mg/kg), and high-dose cyclophosphamide (75—100 mg/kg) followed by hematopoietic stem cell support. The results for Study 1 were supported by results observed in the subset of patients in Study 2 who received the same dose and schedule of Kepivance administered in Study 1. One arm of Study 2 that included patients who received Kepivance for 3 consecutive days prior to initiation of cytotoxic therapy, a dose given on the last day of TBI prior to etoposide, and for 3 consecutive days following infusion of hematopoietic stem cells was prematurely closed by the Safety Committee for lack of efficacy and a trend towards increased severity and duration of oral mucositis as compared to placebo-treated patients. The Safety Committee attributed the safety finding to Kepivance having been administered within 24 hours of chemotherapy, which resulted in an increased sensitivity of the rapidly dividing epithelial cells in the immediate post-chemotherapy period [see DOSAGE AND ADMINISTRATION and DRUG INTERACTIONS].
Lack Of Efficacy: Autologous Transplantation Preparative Regimen Using High Dose Melphalan
In a post approval study, Study 3, designed to determine the efficacy of Kepivance with a high dose melphalan preparative regimen, patients with multiple myeloma were evaluated in a multicenter, randomized, double-blind, placebo-controlled trial. The conditioning regimen was melphalan (200 mg/m²) on day -2 followed by autologous hematopoietic stem cell support. A total of 281 patients were randomized to 3 arms: Kepivance before melphalan on days -6, -5, -4 and after melphalan on days 0, 1, and 2 (pre-post) (n=115); Kepivance before melphalan on days -6, -5, -4 (pre) (n=109); or placebo (n=57).
The main outcome of the study was maximum severity of WHO oral mucositis. The median age of enrolled patients was 57 years (range 32-69), and 55% were male. The results are presented in Figure 2. The prespecified primary analysis was a comparison between the Kepivance pre-post and pre arms to placebo. The incidence of WHO Grade 3 and 4 in the Kepivance pre-post arm was 38%, compared to 37% in the placebo arm. There were no significant differences between either of the Kepivance regimens and the placebo arm in the incidence of severe oral mucositis.
Figure 2: Incidence of Oral Mucositis by Maximum Grade WHO Oral Mucositis Scale in High Dose Melphalan Study
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A subset of subjects enrolled in the multiple myeloma study were included in an evaluation for the risk of cataract development in patients receiving Kepivance treatment. Ophthalmologic examinations were performed on 101 patients enrolled in a double-blind, randomized, placebo-controlled study of two different schedules of Kepivance (pre and post chemotherapy and pre chemotherapy only) for reduction in severity of oral mucositis in subjects with multiple myeloma receiving high dose melphalan followed by autologous peripheral blood stem cell transplantation. For the primary cataract endpoint of incidence of cataract development or cataract progression at Month 12, there was a greater proportion of subjects that experienced cataract development in the Kepivance group: 48% (25/52) compared with the placebo group: 29% (4/14) (difference of 17 [95% CI: -11, 46]) [see ADVERSE REACTIONS].
Lack Of Efficacy: Allogeneic Transplantation
In a post approval study, designed to determine the efficacy of Kepivance in decreasing the incidence of severe acute graft versus host disease (aGVHD) in patients with hematologic malignancies undergoing allogeneic transplantation, the incidence , duration and severity of oral mucositis was also measured. Multiple conditioning regimens were used. Patients were randomized to placebo (n=78) or to Kepivance (n=77) 60 micrograms/kg for 3 doses prior to the conditioning regimen and 180 micrograms/kg at least 24 hours from the last dose of chemotherapy and at least 24 hours before the first dose of post transplant methotrexate. There was no difference in the incidence of severe aGVHD Kepivance (16%) compared to placebo (17%). In addition to the lack of efficacy in preventing severe aGVHD, the incidence of WHO grade 3 and 4 mucositis was nominally higher in patients treated with Kepivance (81%) compared to placebo (73%).
REFERENCES
1 WHO Oral Mucositis Scale: Grade 1 = soreness/erythema; Grade 2 = erythema, ulcers, can eat solids; Grade 3 = ulcers, requires liquid diet only; Grade 4 = alimentation not possible.