Gemcitabine 1 g Injection, Powder, Lyophilized, For Solution, 1 vial — NDC 16714-930-01 (Billing 16714-0930-01)

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action Gemcitabine kills cells undergoing DNA synthesis and blocks the progression of cells through the G1/S-phase boundary. Gemcitabine is metabolized by nucleoside kinases to diphosphate (dFdCDP) and triphosphate (dFdCTP) nucleosides. Gemcitabine diphosphate inhibits ribonucleotide reductase, an enzyme responsible for catalyzing the reactions that generate deoxynucleoside triphosphates for DNA synthesis, resulting in reductions in deoxynucleotide concentrations, including dCTP.

Gemcitabine triphosphate competes with dCTP for incorporation into DNA. The reduction in the intracellular concentration of dCTP by the action of the diphosphate enhances the incorporation of gemcitabine triphosphate into DNA (self-potentiation). After the gemcitabine nucleotide is incorporated into DNA, only one additional nucleotide is added to the growing DNA strands, which eventually results in the initiation of apoptotic cell death.

12.3Pharmacokinetics The pharmacokinetics of gemcitabine were examined in 353 patients with various solid tumors. Pharmacokinetic parameters were derived using data from patients treated for varying durations of therapy given weekly with periodic rest weeks and using both short infusions (<70 minutes) and long infusions (70 to 285 minutes). The total gemcitabine for injection dose varied from 500 mg/m 2 to 3600 mg/m 2 .

Distribution The volume of distribution was increased with infusion length. Volume of distribution of gemcitabine was 50 L/m 2 following infusions lasting <70 minutes. For long infusions, the volume of distribution rose to 370 L/m 2 .

Gemcitabine pharmacokinetics are linear and are described by a 2-compartment model. Population pharmacokinetic analyses of combined single and multiple dose studies showed that the volume of distribution of gemcitabine was significantly influenced by duration of infusion and sex. Gemcitabine plasma protein binding is negligible.

Elimination Metabolism The active metabolite, gemcitabine triphosphate, can be extracted from peripheral blood mononuclear cells. The half-life of the terminal phase for gemcitabine triphosphate from mononuclear cells ranges from 1.7 to 19.4 hours. Excretion Gemcitabine disposition was studied in 5 patients who received a single 1000 mg/m 2 of radiolabeled drug as a 30-minute infusion.

Within one week, 92% to 98% of the dose was recovered, almost entirely in the urine. Gemcitabine (<10%) and the inactive uracil metabolite, 2′-deoxy-2′,2′-difluorouridine (dFdU) accounted for 99% of the excreted dose. The metabolite dFdU is also found in plasma.

Specific Populations Geriatric Patients Clearance of gemcitabine was affected by age. The lower clearance in geriatric patients results in higher concentrations of gemcitabine for any given dose. Differences in either clearance or volume of distribution based on patient characteristics or the duration of infusion result in changes in half-life and plasma concentrations.

Table 15 shows plasma clearance and half-life of gemcitabine following short infusions for typical patients by age and sex. Table 15: Gemcitabine Clearance and Half–Life for the “Typical” Patient a Half–life for patients receiving a <70 minute infusion. Age Clearance Men (L/hr/m 2 ) Clearance Women (L/hr/m 2 ) Half–Life a Men (min) Half–Life a Women (min) 29 92.2 69.4 42 49 45 75.7 57.0 48 57 65 55.1 41.5 61 73 79 40.7 30.7 79 94 Gemcitabine half-life for short infusions ranged from 42 to 94 minutes and for long infusions varied from 245 to 638 minutes, depending on age and sex, reflecting a greatly increased volume of distribution with longer infusions.

Male and Female Patients Females have lower clearance and longer half-lives than male patients as described in Table 15 . Patients with Renal Impairment No clinical studies have been conducted with gemcitabine in patients with decreased renal function. Patients with Hepatic Impairment No clinical studies have been conducted with gemcitabine in patie… [Excerpted — this section continues on DailyMed.]

12.1Mechanism of Action Gemcitabine kills cells undergoing DNA synthesis and blocks the progression of cells through the G1/S-phase boundary. Gemcitabine is metabolized by nucleoside kinases to diphosphate (dFdCDP) and triphosphate (dFdCTP) nucleosides. Gemcitabine diphosphate inhibits ribonucleotide reductase, an enzyme responsible for catalyzing the reactions that generate deoxynucleoside triphosphates for DNA synthesis, resulting in reductions in deoxynucleotide concentrations, including dCTP.

Gemcitabine triphosphate competes with dCTP for incorporation into DNA. The reduction in the intracellular concentration of dCTP by the action of the diphosphate enhances the incorporation of gemcitabine triphosphate into DNA (self-potentiation). After the gemcitabine nucleotide is incorporated into DNA, only one additional nucleotide is added to the growing DNA strands, which eventually results in the initiation of apoptotic cell death.

12.3Pharmacokinetics The pharmacokinetics of gemcitabine were examined in 353 patients with various solid tumors. Pharmacokinetic parameters were derived using data from patients treated for varying durations of therapy given weekly with periodic rest weeks and using both short infusions (<70 minutes) and long infusions (70 to 285 minutes). The total gemcitabine for injection dose varied from 500 mg/m 2 to 3600 mg/m 2 .

Distribution The volume of distribution was increased with infusion length. Volume of distribution of gemcitabine was 50 L/m 2 following infusions lasting <70 minutes. For long infusions, the volume of distribution rose to 370 L/m 2 .

Gemcitabine pharmacokinetics are linear and are described by a 2-compartment model. Population pharmacokinetic analyses of combined single and multiple dose studies showed that the volume of distribution of gemcitabine was significantly influenced by duration of infusion and sex. Gemcitabine plasma protein binding is negligible.

Elimination Metabolism The active metabolite, gemcitabine triphosphate, can be extracted from peripheral blood mononuclear cells. The half-life of the terminal phase for gemcitabine triphosphate from mononuclear cells ranges from 1.7 to 19.4 hours. Excretion Gemcitabine disposition was studied in 5 patients who received a single 1000 mg/m 2 of radiolabeled drug as a 30-minute infusion.

Within one week, 92% to 98% of the dose was recovered, almost entirely in the urine. Gemcitabine (<10%) and the inactive uracil metabolite, 2′-deoxy-2′,2′-difluorouridine (dFdU) accounted for 99% of the excreted dose. The metabolite dFdU is also found in plasma.

Specific Populations Geriatric Patients Clearance of gemcitabine was affected by age. The lower clearance in geriatric patients results in higher concentrations of gemcitabine for any given dose. Differences in either clearance or volume of distribution based on patient characteristics or the duration of infusion result in changes in half-life and plasma concentrations.

Table 15 shows plasma clearance and half-life of gemcitabine following short infusions for typical patients by age and sex. Table 15: Gemcitabine Clearance and Half–Life for the “Typical” Patient a Half–life for patients receiving a <70 minute infusion. Age Clearance Men (L/hr/m 2 ) Clearance Women (L/hr/m 2 ) Half–Life a Men (min) Half–Life a Women (min) 29 92.2 69.4 42 49 45 75.7 57.0 48 57 65 55.1 41.5 61 73 79 40.7 30.7 79 94 Gemcitabine half-life for short infusions ranged from 42 to 94 minutes and for long infusions varied from 245 to 638 minutes, depending on age and sex, reflecting a greatly increased volume of distribution with longer infusions.

Male and Female Patients Females have lower clearance and longer half-lives than male patients as described in Table 15 . Patients with Renal Impairment No clinical studies have been conducted with gemcitabine in patients with decreased renal function. Patients with Hepatic Impairment No clinical studies have been conducted with gemcitabine in patients with decreased hepatic function.

Drug Interaction Studies When gemcitabine for injection (1250 mg/m 2 on Days 1 and 8) and cisplatin (75 mg/m 2 on Day 1) were administered in patients with NSCLC, the clearance of gemcitabine on Day 1 was 128 L/hr/m 2 and on Day 8 was 107 L/hr/m 2 . Data from patients with NSCLC demonstrate that gemcitabine for injection and carboplatin given in combination does not alter the pharmacokinetics of gemcitabine or carboplatin compared to administration of either single agent; however, due to wide confidence intervals and small sample size, interpatient variability may be observed.

Data from metastatic breast cancer patients shows that gemcitabine for injection has little or no effect on the pharmacokinetics (clearance and half-life) of paclitaxel and paclitaxel has little or no effect on the pharmacokinetics of gemcitabine.

14 CLINICAL STUDIES

14.1Ovarian Cancer The efficacy of gemcitabine for injection was evaluated in a randomized trial (Study 1) conducted in women with advanced ovarian cancer that had relapsed at least 6 months after first-line platinum-based therapy. Patients were randomized to receive either gemcitabine for injection 1000 mg/m 2 on Days 1 and 8 of each 21-day cycle with carboplatin AUC 4 on Day 1 after gemcitabine for injection administration (n=178) or carboplatin AUC 5 on Day 1 of each 21-day cycle (n=178). The major efficacy outcome measure was progression free survival (PFS).

A total of 356 patients were enrolled. Demographics and baseline characteristics are shown in Table 16 . Efficacy results are presented in Table 17 and Figure 1 .

The addition of gemcitabine for injection to carboplatin resulted in statistically significant improvements in PFS and overall response rate. Approximately 75% of patients in each arm received additional chemotherapy for disease progression; 13 of 120 patients in the carboplatin alone arm received gemcitabine for injection for treatment of disease progression. There was no significant difference in overall survival between the treatment arms.

Table 16: Baseline Demographics and Clinical Characteristics for Study 1 a 5 patients on gemcitabine for injection with carboplatin arm and 4 patients on carboplatin arm had no baseline Eastern Cooperative Oncology Group (ECOG) performance status. b 2 patients on gemcitabine for injection with carboplatin arm and 1 patient on carboplatin arm had platinum-free interval <6 months. Gemcitabine For Injection/Carboplatin (N=178) Carboplatin (N=178) Median age, years 59 58 Range 36 to 78 21 to 81 Baseline ECOG performance status 0-1 a 94% 95% Disease Status Evaluable 8% 3% Bidimensionally measurable 92% 96% Platinum–free interval b 6-12 months 40% 40% >12 months 59% 60% First–line therapy Platinum–taxane combination 70% 71% Platinum–non–taxane combination 29% 28% Platinum monotherapy 1% 1% Table 17: Efficacy Results in Study 1 a CI=confidence interval. b Log rank, unadjusted. c Chi square. d CR=Complete response. e PR with PRNM=Partial response with partial response, non-measurable disease. f Independently reviewed cohort - gemcitabine for injection/carboplatin (n=121), carboplatin (n=101); independent reviewers unable to measure disease detected by sonography or physical exam.

Efficacy Parameter Gemcitabine For Injection/Carboplatin (N=178) Carboplatin (N=178) Progression-Free Survival Median (95% CI a ) in months 8.6 (8.0, 9.7) 5.8 (5.2, 7.1) Hazard Ratio (95% CI) 0.72 (0.57, 0.90) p-value b p=0.0038 Overall Survival Median (95% CI) in months 18.0 (16.2, 20.3) 17.3 (15.2, 19.3) Hazard Ratio (95% CI) 0.98 (0.78, 1.24) p-value b p=0.8977 Overall Response Rate by Investigator Review 47.2% 30.9% p-value c p=0.0016 CR d 14.6% 6.2% PR with PRNM e 32.6% 24.7% Overall Response Rate f by Independent Review 46.3% 35.6% p-value c p=0.11 CR d 9.1% 4.0% PR with PRNM e 37.2% 31.7% Figure 1: Kaplan-Meier Curves for Progression Free Survival in Study 1 Figure 1

14.2Breast Cancer The efficacy of gemcitabine for injection was evaluated in a multinational, randomized, open-label trial (Study 2) conducted in women receiving initial treatment for metastatic breast cancer and who have received prior adjuvant/neoadjuvant anthracycline chemotherapy unless clinically contraindicated. Patients were randomized to receive either gemcitabine for injection 1250 mg/m 2 on Days 1 and 8 of each 21-day cycle with paclitaxel 175 mg/m 2 administered on Day 1 before gemcitabine for injection administration (n=267) or paclitaxel 175 mg/m 2 on Day 1 of each 21-day cycle (n=262).

The major efficacy outcome measure was time to documented disease progression. A total of 529 patients were enrolled. Demographic and baseline characteristics were similar between treatment arms ( Table 18 ).

Efficacy results are presented in Table 19 and Figure 2 . The addition of gemcitabine for injection to paclit… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Long-term animal studies to evaluate the carcinogenic potential of gemcitabine for injection have not been conducted. Gemcitabine was mutagenic in an in vitro mouse lymphoma (L5178Y) assay and was clastogenic in an in vivo mouse micronucleus assay. Gemcitabine intraperitoneal doses of 0.5 mg/kg/day [about 1/700 the 1000 mg/m 2 clinical dose based on body surface area (BSA)] in male mice resulted in moderate to severe hypospermatogenesis, decreased fertility, and decreased implantations.

In female mice, fertility was not affected but maternal toxicities were observed at 1.5 mg/kg/day administered intravenously (about 1/200 the 1000 mg/m 2 clinical dose based on BSA) and fetotoxicity or embryolethality was observed at 0.25 mg/kg/day administered intravenously (about 1/1300 the 1000 mg/m 2 clinical dose based on BSA).