75607-67-9

Fludarabine phosphate is an antimetabolite indicated for the treatment of B cell lymphocytic leukemia. It is reportedly effective in patients refractory to other therapies. Fludarabine phosphate acts by inhibiting primer RNA synthesis. Its side effects include bone marrow suppression, anemia, thrombocytopenia and neutropenia.

White or almost white, crystalline powder, hygroscopic.

Southern Research Institute (U.S.A.)

anticonvulsant

ChEBI: A purine arabinonucleoside monophosphate having 2-fluoroadenine as the nucleobase. A prodrug, it is rapidly dephosphorylated to 2-fluoro-ara-A and then phosphorylated intracellularly by deoxycytidine kinase to the active triphosphate, 2-fluoro-ara-ATP. Onc incorporated into DNA, 2-fluoro-ara-ATP functions as a DNA chain terminator. It is used for the treatment of adult patients with B-cell chronic lymphocytic leukemia (CLL) who have not responded to, or whose disease has progressed during, treatment with at least one standard alkylating-agent containing regimenas.

Fludara (Berlex).

Fludarabine phosphate is a cytotoxic purine antimetabolite that acts by inhibiting DNA synthesis. Fludarabine and its soluble derivatives interfere with phosphorylation, e.g., in L 1210 cells. Fludarabine behaves more like an analog of deoxycytidine than adenine or deoxyadenine as indicated by reports demonstrating that the presence of fluorine in the 2-position of the adenine ring alters its function as a substrate for deaminase and nucleoside kinases. This results in differences in biological activity and metabolism. Halogenation does not simply block deamination, but also influences the enzyme that carries out the phosphorylation, as a result cytotoxicity is increased. Fludarabine phosphate may selectively inhibit the incorporation of thymidine and uridine into the DNA molecule by inhibiting both ribonucleotide reductase and DNA polymerase. The maximum tolerated dose (MTD) in heavily pretreated patients with advanced malignancy/solid tumors on the daily regimen was about 15 mg/m2. Granulocytopenia and thrombocytopenia were dose-limiting.

Fludarabine phosphate is rapidly dephosphorylated to 2-fluoro-ara-A and then phosphorylated intracellularly by deoxycytidine kinase to the active triphosphate, 2-fluoro-ara-ATP. This metabolite appears to act by inhibiting DNA polymerase alpha, ribonucleotide reductase and DNA primase, thus inhibiting DNA synthesis. The mechanism of action of this antimetabolite is not completely characterized and may be multi-faceted.
Phase I studies in humans have demonstrated that fludarabine phosphate is rapidly converted to the active metabolite, 2-fluoro-ara-A, within minutes after intravenous infusion.
Consequently, clinical pharmacology studies have focused on 2-fluoro-ara-A pharmacokinetics. After the five daily doses of 25 mg 2-fluoro-ara-AMP/m2 to cancer patients infused over 30 minutes, 2-fluoro-ara-A concentrations show a moderate accumulation. During a 5-day treatment schedule, 2-fluoro-ara-A plasma trough levels increased by a factor of about 2. The terminal half-life of 2-fluoro-ara-A was estimated as approximately 20 hours. In vitro, plasma protein binding of fludarabine ranged between 19% and 29%.

Fludarabine phosphate (Fludara ® ), is a fluorinated nucleotide analog of the antiviral agent vidarabine, 9-β-D-arabinofuranosyladenine(ara-A), which differs only by the presence of a fluorine atom at position 2 of the purine moiety and a phosphate group at position 5 of the arabinose moiety (Plunkett et al., 1993). These structural modifications result in increased aqueous solubility and resistance to enzymatic degradation by adenosine deaminases compared to vidarabine (Brockman et al., 1977; Plunkett et al., 1990). Fludarabine phosphate is indicated for the treatment of patients with B-cell chronic lymphocytic leukemia (CLL) who have not responded to or whose disease has progressed during treatment with at least one standard alkylating agent containing regimen (Boogaerts et al., 2001; Rossi et al., 2004).

The general procedure for the synthesis of ((2R,3S,4S,5R)-5-(6-amino-2-fluoro-9H-purin-9-yl)-3,4-dihydroxytetrahydrofuran-2-yl)methylphosphonic acid dihydrogen ester from 2-fluoroadenosine is as follows: Example 1: Fludarabine (19.5 g, 0.0683 mol) and triethylphosphate (79.1 ml, 0.465 mol) were added to a reactor pre-cooled to -15/-20°C. Trichlorophosphate (15.3 ml, 0.164 mole) was added slowly and dropwise over a period of about 1 hour while the reaction temperature was controlled to be maintained at -10/-15°C. The reaction mixture was stirred continuously for 48 hours until HPLC analysis showed that the amount of fludarabine was less than 2%. Subsequently, pre-cooled toluene (780 ml, 40 v/v) was slowly added over a period of about 1.5 hours and stirring was continued for 1-2 hours at -10/-15°C. The reaction was completed by filtration and the filter cake was washed with toluene (20 ml). The wetted solid (ca. 35 g) was suspended in water (40 ml) and the pH was adjusted to 11 with 32% sodium hydroxide solution (ca. 20 ml). the resulting solution was transferred to Dowex resin that had been pretreated (activation and washing: washed sequentially with softened water to colorless, acidified with 5% hydrochloric acid (ca. 200 ml), and washed with softened water to a neutral pH). Filtration is carried out after stirring for 15 minutes. The resin was again suspended in water (500 ml), stirred for 15 minutes and filtered. This was repeated until no fludarabine phosphate was detected in the filtrate. The product-containing filtrates were combined and concentrated under reduced pressure at 30-35°C until the product began to precipitate, filtered and dried under vacuum at 60°C to constant weight to give 10 g of white solid (40% yield) with >97.5% purity. Recrystallization step: the above solid was suspended in 10 volumes of water, heated at 70°C for 1 hour, hot filtered, and the filter cake was washed with acetone to obtain a white solid with purity >99%.

DNA synthesis

Potentially hazardous interactions with other drugs
Antipsychotics: avoid concomitant use with clozapine, increased risk of agranulocytosis.
Cytotoxics: increased pulmonary toxicity with pentostatin (unacceptably high incidence of fatalities); increases intracellular concentration of cytarabine.

Intravenous fludarabine phosphate is rapidly dephosphorylated to fludarabine which is taken up by lymphocytes and rephosphorylated via the enzyme deoxycytidine kinase to the active triphosphate nucleotide. Clearance of fludarabine from the plasma is triphasic; elimination is mostly via renal excretion: 40-60% of an intravenous dose is excreted in the urine. The pharmacokinetics of fludarabine show considerable inter-individual variation

[1] Patent: WO2005/40183, 2005, A2. Location in patent: Page/Page column 4-5
[2] Advanced Synthesis and Catalysis, 2014, vol. 356, # 2-3, p. 563 - 570