Docetaxel is an antineoplastic agent belonging to the taxoid family. It is prepared by semisynthesis beginning with a precursor extracted from the renewable needle biomass of yew plants. The chemical name for docetaxel is (2R,3S)-N-carboxy-3-phenylisoserine,N- tert -butyl ester, 13-ester with 5β-20-epoxy-1,2α,4,7β,10β,13α-hexahydroxytax-11-en-9-one 4-acetate 2-benzoate. Docetaxel has the following structural formula:
Docetaxel is a white to off-white powder with an empirical formula of C 43 H 53 NO 14 , and a molecular weight of 807.88. It is highly lipophilic and practically insoluble in water.
One-vial Docetaxel Injection
Docetaxel Injection USP is a sterile, non-pyrogenic, pale-yellow to brownish-yellow solution at 20 mg/mL concentration.
Each mL contains 20 mg docetaxel anhydrous USP, in 4 mg anhydrous citric acid, 520 mg polysorbate 80 and 395 mg dehydrated alcohol solution.
Docetaxel Injection USP is available in multiple dose (20 mg/mL, 80 mg/4 mL and 160 mg/8 mL) vials containing 20 mg (1 mL), 80 mg (4 mL) or 160 mg (8 mL) docetaxel anhydrous USP.
Docetaxel Injection USP requires NO prior dilution with a diluent and is ready to add to the infusion solution.
Docetaxel is an antineoplastic agent that acts by disrupting the microtubular network in cells that is essential for mitotic and interphase cellular functions. Docetaxel binds to free tubulin and promotes the assembly of tubulin into stable microtubules while simultaneously inhibiting their disassembly. This leads to the production of microtubule bundles without normal function and to the stabilization of microtubules, which results in the inhibition of mitosis in cells. Docetaxel’s binding to microtubules does not alter the number of protofilaments in the bound microtubules, a feature which differs from most spindle poisons currently in clinical use.
The pharmacokinetics of docetaxel has been evaluated in cancer patients after administration of 20 mg/m 2 to 115 mg/m 2 in phase 1 studies. The area under the curve (AUC) was dose proportional following doses of 70 mg/m 2 to 115 mg/m 2 with infusion times of 1 to 2 hours. Docetaxel’s pharmacokinetic profile is consistent with a three-compartment pharmacokinetic model, with half-lives for the α, β, and γ phases of 4 min, 36 min, and 11.1 hr, respectively. Mean total body clearance was 21 L/h/m 2.
The initial rapid decline represents distribution to the peripheral compartments and the late (terminal) phase is due, in part, to a relatively slow efflux of docetaxel from the peripheral compartment. Mean steady state volume of distribution was 113 L. In vitro studies showed that docetaxel is about 94% protein bound, mainly to α 1 -acid glycoprotein, albumin, and lipoproteins. In three cancer patients, the in vitro binding to plasma proteins was found to be approximately 97%. Dexamethasone does not affect the protein binding of docetaxel.
In vitro drug interaction studies revealed that docetaxel is metabolized by the CYP3A4 isoenzyme, and its metabolism may be modified by the concomitant administration of compounds that induce, inhibit, or are metabolized by cytochrome P450 3A4 [see Drug Interactions (7)].
A study of 14 C-docetaxel was conducted in three cancer patients. Docetaxel was eliminated in both the urine and feces following oxidative metabolism of the tert -butyl ester group, but fecal excretion was the main elimination route. Within 7 days, urinary and fecal excretion accounted for approximately 6% and 75% of the administered radioactivity, respectively. About 80% of the radioactivity recovered in feces is excreted during the first 48 hours as 1 major and 3 minor metabolites with very small amounts (less than 8%) of unchanged drug.
Effect of Age: A population pharmacokinetic analysis was carried out after docetaxel treatment of 535 patients dosed at 100 mg/m 2. Pharmacokinetic parameters estimated by this analysis were very close to those estimated from phase 1 studies. The pharmacokinetics of docetaxel was not influenced by age.
Effect of Gender: The population pharmacokinetics analysis described above also indicated that gender did not influence the pharmacokinetics of docetaxel.
Hepatic Impairment: The population pharmacokinetic analysis described above indicated that in patients with clinical chemistry data suggestive of mild to moderate liver impairment (AST and/or ALT >1.5 times ULN concomitant with alkaline phosphatase >2.5 times ULN), total body clearance was lowered by an average of 27%, resulting in a 38% increase in systemic exposure (AUC). This average, however, includes a substantial range and there is, at present, no measurement that would allow recommendation for dose adjustment in such patients. Patients with combined abnormalities of transaminase and alkaline phosphatase should not be treated with Docetaxel Injection. Patients with severe hepatic impairment have not been studied [see Warnings and Precautions (5.2), Use in Specific Populations (8.6)].
Effect of Race: Mean total body clearance for Japanese patients dosed at the range of 10 mg/m 2 to 90 mg/m 2 was similar to that of European/American populations dosed at 100 mg/m 2 , suggesting no significant difference in the elimination of docetaxel in the two populations.
Drug Interaction StudiesEffect of Ketoconazole: The effect of ketoconazole (a strong CYP3A4 inhibitor) on the pharmacokinetics of docetaxel was investigated in 7 cancer patients. Patients were randomized to receive either docetaxel (100 mg/m 2 intravenous) alone or docetaxel (10 mg/m 2 intravenous) in combination with ketoconazole (200 mg orally once daily for 3 days) in a crossover design with a 3-week washout period. The results of this study indicated that the mean dose-normalized AUC of docetaxel was increased 2.2-fold and its clearance was reduced by 49% when docetaxel was coadministered with ketoconazole [see Dosage and Administration (2.7), Drug Interactions (7)]
Effect of combination therapies
- Dexamethasone: Docetaxel total body clearance was not modified by pretreatment with dexamethasone.
- Cisplatin: Clearance of docetaxel in combination therapy with cisplatin was similar to that previously observed following monotherapy with docetaxel. The pharmacokinetic profile of cisplatin in combination therapy with docetaxel was similar to that observed with cisplatin alone.
- Cisplatin and Fluorouracil: The combined administration of docetaxel, cisplatin and fluorouracil in 12 patients with solid tumors had no influence on the pharmacokinetics of each individual drug.
- Prednisone: A population pharmacokinetic analysis of plasma data from 40 patients with metastatic castration-resistant prostate cancer indicated that docetaxel systemic clearance in combination with prednisone is similar to that observed following administration of docetaxel alone.
- Cyclophosphamide and Doxorubicin: A study was conducted in 30 patients with advanced breast cancer to determine the potential for drug-drug interactions between docetaxel (75 mg/m 2), doxorubicin (50 mg/m 2), and cyclophosphamide (500 mg/m 2) when administered in combination. The coadministration of docetaxel had no effect on the pharmacokinetics of doxorubicin and cyclophosphamide when the three drugs were given in combination compared to coadministration of doxorubicin and cyclophosphamide only. In addition, doxorubicin and cyclophosphamide had no effect on docetaxel plasma clearance when the three drugs were given in combination compared to historical data for docetaxel monotherapy.
Carcinogenicity studies with docetaxel have not been performed.
Docetaxel was clastogenic in the in vitro chromosome aberration test in CHO-K 1 cells and in the in vivo micronucleus test in mice administered doses of 0.39 to 1.56 mg/kg (about 1/60 th to 1/15 th the recommended human dose on a mg/m 2 basis). Docetaxel was not mutagenic in the Ames test or the CHO/HGPRT gene mutation assays.
Docetaxel did not reduce fertility in rats when administered in multiple intravenous doses of up to 0.3 mg/kg (about 1/50 th the recommended human dose on a mg/m 2 basis), but decreased testicular weights were reported. This correlates with findings of a 10-cycle toxicity study (dosing once every 21 days for 6 months) in rats and dogs in which testicular atrophy or degeneration was observed at intravenous doses of 5 mg/kg in rats and 0.375 mg/kg in dogs (about 1/3 rd and 1/15 th the recommended human dose on a mg/m 2 basis, respectively). An increased frequency of dosing in rats produced similar effects at lower dose levels.
The efficacy and safety of docetaxel have been evaluated in locally advanced or metastatic breast cancer after failure of previous chemotherapy (alkylating agent-containing regimens or anthracycline-containing regimens).
In one randomized trial, patients with a history of prior treatment with an anthracycline containing regimen were assigned to treatment with docetaxel (100 mg/m 2 every 3 weeks) or the combination of mitomycin (12 mg/m 2 every 6 weeks) and vinblastine (6 mg/m 2 every 3 weeks). Two hundred three patients were randomized to docetaxel and 189 to the comparator arm. Most patients had received prior chemotherapy for metastatic disease; only 27 patients on the docetaxel arm and 33 patients on the comparator arm entered the study following relapse after adjuvant therapy. Three-quarters of patients had measurable, visceral metastases. The primary endpoint was time to progression. The following table summarizes the study results (See Table 12.)
|Efficacy Parameter||Docetaxel (n=203)||Mitomycin/Vinblastine (n=189)||p-value|
|Median Survival||11.4 months||8.7 months|
|Risk Ratio *, Mortality (Docetaxel: Control)||0.73||p=0.01 Log Rank|
|95% CI (Risk Ratio)||0.58-0.93|
|Median Time to Progression||4.3 months||2.5 months|
|Risk Ratio *, Progression (Docetaxel: Control)||0.75||p=0.01 Log Rank|
|95% CI (Risk Ratio)||0.61-0.94|
|Overall Response Rate||28.1%||9.5%||p<0.0001|
|Complete Response Rate||3.4%||1.6%||Chi Square|
In a second randomized trial, patients previously treated with an alkylating-containing regimen were assigned to treatment with docetaxel (100 mg/m 2) or doxorubicin (75 mg/m 2) every 3 weeks. One hundred sixty-one patients were randomized to docetaxel and 165 patients to doxorubicin. Approximately one-half of patients had received prior chemotherapy for metastatic disease, and one-half entered the study following relapse after adjuvant therapy. Three-quarters of patients had measurable, visceral metastases. The primary endpoint was time to progression. The study results are summarized below (See Table 13.)
|Efficacy Parameter||Docetaxel (n=161)||Doxorubicin (n=165)||p-value|
|Median Survival||14.7 months||14.3 months|
|Risk Ratio *, Mortality (Docetaxel: Control)||0.89||p=0.39 Log Rank|
|95% CI (Risk Ratio)||0.68-1.16|
|Median Time to Progression||6.5 months||5.3 months|
|Risk Ratio *, Progression (Docetaxel: Control)||0.93||p=0.45 Log Rank|
|95% CI (Risk Ratio)||0.71-1.16|
|Overall Response Rate||45.3%||29.7%||p=0.004|
|Complete Response Rate||6.8%||4.2%||Chi Square|
In another multicenter open-label, randomized trial (TAX313), in the treatment of patients with advanced breast cancer who progressed or relapsed after one prior chemotherapy regimen, 527 patients were randomized to receive docetaxel monotherapy 60 mg/m 2 (n=151), 75 mg/m 2 (n=188) or 100 mg/m 2 (n=188). In this trial, 94% of patients had metastatic disease and 79% had received prior anthracycline therapy. Response rate was the primary endpoint. Response rates increased with docetaxel dose: 19.9% for the 60 mg/m 2 group compared to 22.3% for the 75 mg/m 2 and 29.8% for the 100 mg/m 2 group; pair-wise comparison between the 60 mg/m 2 and 100 mg/m 2 groups was statistically significant (p=0.037).
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