Gemcitabine

Absorption

Peak plasma concentrations of gemcitabine range from 10 to 40 mg/L following a 30-minute intravenous infusion, and are reached at 15 to 30 minutes. One study showed that steady-state concentrations of gemcitabine showed a linear relationship to dose over the dose range 53 to 1000 mg/m2. Gemcitabine triphosphate, the active metabolite of gemcitabine, can accumulate in circulating peripheral blood mononuclear cells. In one study, the Cmax of gemcitabine triphosphate in peripheral blood mononuclear cells occurred within 30 minutes of the end of the infusion period and increased increased proportionally with gemcitabine doses of up to 350 mg/m2.

Toxicity

The oral LD50 is 333 mg/kg in mice and >500 mg/kg in rats. The dermal LD50 in rabbits is >1000 mg/kg.
There is no known antidote for gemcitabine overdose. In a dose-escalation study, patients were administered a single dose of gemcitabine as high as 5700 mg/m2 administered by intravenous infusion over 30 minutes every two weeks: main observed toxicities were myelosuppression, paresthesia, and severe rash. In the event of a suspected drug overdose, blood counts should be monitored, and patients should be provided with supportive therapy, as necessary.

Description

Gemcitabine is an anticancer nucleoside analog that inhibits the growth of HL-60 promyelocytic leukemia cells with an LC₅₀ value of 40 nM. It inhibits the growth of MX-1 mammary, CX-1, HC-1, GC3, and VRC5 colon, LX-1, Calu-6, and NCI-H460 lung, and HS766T, PaCa-2, PANC-1, and BxPC-3 pancreatic cancer tumors in mouse xenograft models (45-93% inhibition). Gemcitabine is a prodrug that is metabolized to a diphosphate and triphosphate form in cells. The triphosphate form is incorporated into DNA which induces masked chain termination and cell death. By specifically inhibiting growth arrest and DNA damage inducible protein 45 a (Gadd45a), a key mediator of active DNA demethylation, gemcitabine, at concentrations ranging from 34 to 134 nM, inhibits repair-mediated DNA demethylation in a methylation-sensitive reporter assay. Gemcitabine also has broad antiretroviral activity, decreasing MuLV cell infectivity, a murine AIDS model, in cell culture (EC₅₀ = ~1.5 nM) and inhibits the progression of murine AIDS in vivo at a dose of 1-2 mg/kg per day.

Originator

Gemzar,Lilly Co.

The Uses of Gemcitabine

Gemcitabine(Gemzar) belongs to the group of medicines called antimetabolites. It is used alone or in combination with other medicines to treat cancer of the breast, ovary, pancreas, and lung. Gemcitabine interferes with the growth of cancer cells, which a

The Uses of Gemcitabine

Gemcitabine is used for breast cancer treatment. First-line treatment for locally advanced pancreatic cancer.

Background

Gemcitabine is a nucleoside analog and a chemotherapeutic agent. It was originally investigated for its antiviral effects, but it is now used as an anticancer therapy for various cancers. Gemcitabine is a cytidine analog with two fluorine atoms replacing the hydroxyl on the ribose. As a prodrug, gemcitabine is transformed into its active metabolites that work by replacing the building blocks of nucleic acids during DNA elongation, arresting tumour growth and promoting apoptosis of malignant cells. The structure, metabolism, and mechanism of action of gemcitabine are similar to cytarabine, but gemcitabine has a wider spectrum of antitumour activity.
Gemcitabine is marketed as Gemzar and it is available as intravenous injection. It is approved by the FDA to treat advanced ovarian cancer in combination with carboplatin, metastatic breast cancer in combination with paclitaxel, non-small cell lung cancer in combination with cisplatin, and pancreatic cancer as monotherapy. It is also being investigated in other cancer and tumour types.

Indications

Gemcitabine is a chemotherapeutic agent used as monotherapy or in combination with other anticancer agents.
In combination with carboplatin, it is indicated for the treatment of advanced ovarian cancer that has relapsed at least 6 months after completion of platinum-based therapy.
Gemcitabine in combination with paclitaxel is indicated for the first-line treatment of patients with metastatic breast cancer after failure of prior anthracycline-containing adjuvant chemotherapy, unless anthracyclines were clinically contraindicated.
In combination with cisplatin, gemcitabine is indicated for the first-line treatment of patients with inoperable, locally advanced (Stage IIIA or IIIB) or metastatic (Stage IV) non-small cell lung cancer (NSCLC). Dual therapy with cisplatin is also used to treat patients with Stage IV (locally advanced or metastatic) transitional cell carcinoma (TCC) of the bladder.
Gemcitabine is indicated as first-line treatment for patients with locally advanced (nonresectable Stage II or Stage III) or metastatic (Stage IV) adenocarcinoma of the pancreas. Gemcitabine is indicated for patients previously treated with fluorouracil.

What are the applications of Application

2′-Deoxy-2′,2′-difluorocytidine is an irreversible inactivator of bacterial ribonucleoside diphosphate reductase

Indications

Gemcitabine (Gemzar), an antimetabolite, undergoes metabolic activation to difluorodeoxycytidine triphosphate, which interferes with DNA synthesis and repair. It is the single most active agent for the treatment of metastatic pancreatic cancer, and it is used as a first-line treatment for both pancreatic and small cell lung cancer. It is administered by intravenous infusion. The dose-limiting toxicity is bone marrow suppression.

Definition

ChEBI: Gemcitabine is a 2'-deoxycytidine having geminal fluoro substituents in the 2'-position. An inhibitor of ribonucleotide reductase, gemcitabine is used in the treatment of various carcinomas, particularly non-small cell lung cancer, pancreatic cancer, bladder cancer and breast cancer. It has a role as a photosensitizing agent, a DNA synthesis inhibitor, a prodrug, an EC 1.17.4.1 (ribonucleoside-diphosphate reductase) inhibitor, an environmental contaminant, a xenobiotic, a radiosensitizing agent, an antineoplastic agent, an antimetabolite, an antiviral drug and an immunosuppressive agent. It is an organofluorine compound and a pyrimidine 2'-deoxyribonucleoside.

Manufacturing Process

Benzyl 4,6-O-benzylidene-2-O-benzyl-3-oxo-α-D-gluco-pyranoside was obtained by 4 steps from glucose.
0.53 ml (4.0 mmol) of DAST (fluorinaiting agent) was added to asolution of 300 mg (0.67 mmol) of benzyl 4,6-O-benzylidene-2-O-benzyl-3-oxo-α-Dgluco-pyranoside in anhydrous dichloromethane (4 ml). The solution was then stirred at room temperature for 2 h, and the excess of DAST was neutralized by careful addition of saturated aqueous NaHCO3. The resulting mixture was extracted with CH2Cl2, and organic phase was dried and evaporated. The residue was purified by CC (Hexane/Ethyl acetate 7:1) to afford benzyl 4,6-Obenzylidene-2-O-benzyl-3-deoxy-3,3-difluoro-α-D-gluco-pyranoside (189 mg, 60%), melting point 118°-119°C.
Benzyl 4,6-O-benzylidene-2-O-benzyl-3-deoxy-3,3-difluoro-α-D-glucopyranoside (77 mg, 0.16 mmol) was dissolved in a 0.1 N solution of HCl in ethanol and stirred at room temperature for 40 h. The solution was then neutralized with solid NaHCO3, filtered and evaporated to give an oily product that was dissolved in 2 ml of CH2Cl2 and 0.5 ml of pyridine. After cooling to 0°C, 0.40 ml (1.6 mmol) of benzoyl chloride was added and the solution was stirred for 1 h and poured into ice and water (200 ml) containing NaHCO3, extracted several times with CH2Cl2, dried and evaporated to give 86 mg (0.14 mmol, 90%) of benzyl 4,6-di-O-benzoyl-2-O-benzyl-3-deoxy-3,3- difluoro-α-D-gluco-pyranoside.
Benzyl 4,6-di-O-benzoyl-2-O-benzyl-3-deoxy-3,3-difluoro-α-D-glucopyranoside (220 mg, 0.44 mmol) was dissolved in methanol in the presence of 200 mg of palladium on activated charcoal (10% Pd content). The suspension was stirred at room temperature under hydrogen pressure (10 bar) for 16 h. The suspension was then filtered through a thin silica gel pad, and evaporated. The residue was purified by CC to give 105 mg (59%) of 4,6- di-O-benzoyl-3-deoxy-3,3-difluoro-α/β-D-gluco-pyranoside as an inseparable anomeric mixture (ratio α/β = 5:1).
To a solution of 46 mg (0.11 mmol) of 4,6-di-O-benzoyl-3-deoxy-3,3-difluoro- α/β-D-gluco-pyranoside in water-dioxane 1:2 (2 ml) was added 120 mg (0.56 mmol) of sodium periodate. This resulting solution was stirred at room temperature for 20 h. Then, more sodium periodate (55 mg, 0.26 mmol) was added and stirring was continued for 6 h. After that, the solvents were evaporated and the solid was repeatedly extracted with ethyl acetate (total volume 70 ml). The solvent was then evaporated to give a solid that was treated for 15 min with a diluted (0.1%) methanolic solution of ammonia. THE solution was evaporated and the crude purified by preparative TLC (hexane/ethyl acetate 2:1) to yield 18 mg (0.04 mmol, 43%) of α-3,5-di-Obenzoyl-2-deoxy-2,2-difluoro-D-ribose.

Therapeutic Function

Antineoplastic, Antiviral

General Description

The drug is available as the hydrochloride salt in 200- and1,000-mg lyophilized single-dose vials for IV use.Gemcitabine is used to treat bladder cancer, breast cancer,pancreatic cancer, and NSCLC. Gemcitabine is a potent radiosensitizer,and it increases the cytotoxicity of cisplatin.The mechanism of action of this fluorine-substituted deoxycytidineanalog involves inhibition of DNA synthesis andfunction via DNA chain termination. The triphosphatemetabolite is incorporated into DNA inhibiting severalDNA polymerases and incorporated into RNA inhibitingproper function of mRNA. Resistance can occur because ofdecreased expression of the activation enzyme deoxycytidinekinase or decreased drug transport as well as increasedexpression of catabolic enzymes. Drug oral bioavailabilityis low because of deamination within the GI tract, and thedrug does not cross the blood-brain barrier. Metabolism bydeamination to 2', 2'-difluorouridine (dFdU) is extensive.Drug toxicity includes myelosuppression, fever, malaise,chills, headache, myalgias, nausea, and vomiting.

Hazard

Human systemic effects

Mechanism of action

Gemcitabine shows good activity against human leukemic cell lines, a number of murine solid tumors, and human tumor xenografts. Gemcitabine was significantly more cytotoxic than cytarabine in Chinese hamster ovary cells. The major cellular metabolite is the 5'-triphosphate of gemcitabine. The cytotoxicity was competitively reversed by deoxycytidine, suggesting that the biological activity required phosphorylation by deoxycytidine kinase. Tumor-bearing mice were treated with either gemcitabine or cytarabine (20 mg/kg). DNA synthesis reached 1 % of control levels upon administration of gemcitabine. The greater accumulation of gemcitabine-5'-triphosphate compared with cytarabine-5'-triphosphate may cause greater cytotoxicity and therapeutic activity. Further gemcitabine may enhance its own cytotoxic effects by self-potentiation mechanisms that act on, e. g., deoxycytidine monophosphate deaminase, deoxycytidine kinase or on DNA synthesis.

Pharmacokinetics

Gemcitabine is a nucleoside analog that mediates its antitumour effects by promoting apoptosis of malignant cells undergoing DNA synthesis. More specifically, it blocks the progression of cells through the G1/S-phase boundary. Gemcitabine demonstrated cytotoxic effects against a broad range of cancer cell lines in vitro. It displayed schedule-dependent antitumour activity in various animal models and xenografts from human non-small cell lung cancer (NSCLC) and pancreatic cancer. Therefore, the antineoplastic effects of gemcitabine are enhanced through prolonged infusion time rather than higher dosage. Gemcitabine inhibited the growth of human xenografts from carcinoma of the lung, pancreas, ovaries, head and neck, and breast. In mice, gemcitabine inhibited the growth of human tumour xenografts from the breast, colon, lung or pancreas by 69 to 99%. In clinical trials of advanced NSCLC, gemcitabine monotherapy produced objective response rates ranging from 18 to 26%, with a median duration of response ranging from 3.3 to 12.7 months. Overall median survival time was 6.2 to 12.3 months. The combined use of cisplatin and gemcitabine produced better objective response rates compared to monotherapy. In patients with advanced pancreatic cancer, objective response rates in patients ranged from 5.to 12%, with a median survival duration of 3.9 to 6.3 months. In Phase II trials involving patients with metastatic breast cancer, treatment with gemcitabine alone or with adjuvant chemotherapies resulted in response rate ranging from 13 to 42% and median survival duration ranging from 11.5 to 17.8 months. In metastatic bladder cancer, gemcitabine has a response rate 20 to 28%. In Phase II trials of advanced ovarian cancer, patients treated with gemcitabine had response rate of 57.1%, with progression free survival of 13.4 months and median survival of 24 months.
Gemcitabine causes dose-limiting myelosuppression, such as anemia, leukopenia, neutropenia, and thrombocytopenia; however, events leading to discontinuation tend to occur less than 1% of the patients. Gemcitabine can elevate ALT, AST and alkaline phosphatase levels.

Clinical Use

Antineoplastic agent:

Palliative treatment, or first-line treatment with cisplatin, of locally advanced or metastatic non-small cell lung cancer

Pancreatic, ovarian and breast cancer

Bladder cancer in combination with cisplatin

Drug interactions

Potentially hazardous interactions with other drugs
Antipsychotics: avoid with clozapine, increased risk of agranulocytosis.

Metabolism

Following administration and uptake into cancer cells, gemcitabine is initially phosphorylated by deoxycytidine kinase (dCK), and to a lower extent, the extra-mitochondrial thymidine kinase 2 to form gemcitabine monophosphate (dFdCMP). dFdCMP is subsequently phosphorylated by nucleoside kinases to form active metabolites, gemcitabine diphosphate (dFdCDP) and gemcitabine triphosphate (dFdCTP). Gemcitabine is also deaminated intracellularly and extracellularly by cytidine deaminase to its inactive metabolite 2′,2′-difluorodeoxyuridine or 2′-deoxy-2′,2′-difluorouridine (dFdU). Deamination occurs in the blood, liver, kidneys, and other tissues, and this metabolic pathway accounts for most of drug clearance.

Metabolism

After intravenous doses gemcitabine is rapidly cleared from the blood and metabolised by cytidine deaminase in the liver, kidney, blood, and other tissues. Clearance is about 25% lower in women than in men.
Almost all (99%) of the dose is excreted in urine as 2′-deoxy-2′,2′-difluorouridine (dFdU), only about 1% being found in the faeces. Intracellular metabolism produces mono-, di-, and triphosphate metabolites, the latter two active. The active intracellular metabolites have not been detected in plasma or urine.

References

[1] karnitz lm, flatten ks, wagner jm, et al. gemcitabine-induced activation of checkpoint signaling pathways that affect tumor cell survival. mol pharmacol, 2005, 68 (6): 1636-1644.
[2] ando t, ichikawa j, okamoto a, et al. gemcitabine inhibits viability, growth, and metastasis of osteosarcoma cell lines. j orthop res, 2005, 23 (4): 964-969.
[3] clouser cl, holtz cm, mullett m, et al. analysis of the ex vivo and in vivo antiretroviral activity of gemcitabine. plos one, 2011, 6 (1): e15840.