FLUDARABINE PHOSPHATE- fludarabine phosphate injection, powder, lyophilized, for solution
Fludarabine phosphate for injection should be administered under the supervision of a qualified physician experienced in the use of antineoplastic therapy. Fludarabine phosphate for injection can severely suppress bone marrow function. When used at high doses in dose-ranging studies in patients with acute leukemia, fludarabine phosphate for injection was associated with severe neurologic effects, including blindness, coma, and death. This severe central nervous system toxicity occurred in 36% of patients treated with doses approximately four times greater (96 mg/m 2 /day for 5 to 7 days) than the recommended dose. Similar severe central nervous system toxicity, including coma, seizures, agitation and confusion, has been reported in patients treated at doses in the range of the dose recommended for chronic lymphocytic leukemia.
Instances of life-threatening and sometimes fatal autoimmune phenomena such as hemolytic anemia, autoimmune thrombocytopenia/thrombocytopenic purpura (ITP), Evans syndrome, and acquired hemophilia have been reported to occur after one or more cycles of treatment with fludarabine phosphate for injection. Patients undergoing treatment with fludarabine phosphate for injection should be evaluated and closely monitored for hemolysis.
In a clinical investigation using fludarabine phosphate for injection in combination with pentostatin (deoxycoformycin) for the treatment of refractory chronic lymphocytic leukemia (CLL), there was an unacceptably high incidence of fatal pulmonary toxicity. Therefore, the use of fludarabine phosphate for injection in combination with pentostatin is not recommended.
Fludarabine Phosphate for Injection, USP contains fludarabine phosphate, a fluorinated nucleotide analog of the antiviral agent vidarabine, 9-β-D-arabinofuranosyladenine (ara-A) that is relatively resistant to deamination by adenosine deaminase. Each vial of sterile lyophilized solid cake contains 50 mg of the active ingredient fludarabine phosphate, USP, 50 mg of mannitol, USP, and sodium hydroxide to adjust pH to 7.7. The pH range for the final product is 7.2 to 8.2. Reconstitution with 2 mL of Sterile Water for Injection, USP results in a solution containing 25 mg per mL of fludarabine phosphate, USP, intended for intravenous administration.
The chemical name for fludarabine phosphate, USP is 9 H-Purin-6-amine, 2-fluoro-9-(5- 0-phosphono-β-D-arabino-furanosyl) (2-fluoro-ara-AMP). The molecular formula of fludarabine phosphate, USP is C 10 H 13 FN 5 O 7 P (MW 365.2) and the structure is:
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/m 2 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%.
A correlation was noted between the degree of absolute granulocyte count nadir and increased area under the concentration x time curve (AUC).
Limited pharmacokinetic data for fludarabine phosphate for injection are available from a published study of children (ages 1 to 21 years) with refractory acute leukemias or solid tumors (Children’s Cancer Group Study 097 1). When fludarabine phosphate for injection was administered as a loading dose over 10 minutes immediately followed by a 5-day continuous infusion, steady-state conditions were reached early.
The total body clearance of the principal metabolite 2-fluoro-ara-A correlated with the creatinine clearance, indicating the importance of the renal excretion pathway for the elimination of the drug. Renal clearance represents approximately 40% of the total body clearance. Patients with creatinine clearance 30 to 79 mL/min should have their fludarabine dose reduced and be monitored closely for excessive toxicity. Due to insufficient data, fludarabine phosphate for injection should not be administered to patients with creatinine clearance less than 30 mL/min. (See DOSAGE AND ADMINISTRATION section.)
Two single-arm open-label studies of fludarabine phosphate for injection have been conducted in adult patients with CLL refractory to at least one prior standard alkylating-agent containing regimen. In a study conducted by M.D. Anderson Cancer Center (MDAH), 48 patients were treated with a dose of 22 to 40 mg/m 2 daily for 5 days every 28 days. Another study conducted by the Southwest Oncology Group (SWOG) involved 31 patients treated with a dose of 15 to 25 mg/m 2 daily for 5 days every 28 days. The overall objective response rates were 48% and 32% in the MDAH and SWOG studies, respectively. The complete response rate in both studies was 13%; the partial response rate was 35% in the MDAH study and 19% in the SWOG study. These response rates were obtained using standardized response criteria developed by the National Cancer Institute CLL Working Group 3 and were achieved in heavily pretreated patients. The ability of fludarabine phosphate for injection to induce a significant rate of response in refractory patients suggests minimal cross-resistance with commonly used anti-CLL agents.
The median time to response in the MDAH and SWOG studies was 7 weeks (range of 1 to 68 weeks) and 21 weeks (range of 1 to 53 weeks) respectively. The median duration of disease control was 91 weeks (MDAH) and 65 weeks (SWOG). The median survival of all refractory CLL patients treated with fludarabine phosphate for injection was 43 weeks and 52 weeks in the MDAH and SWOG studies, respectively.
Rai stage improved to Stage II or better in 7 of 12 MDAH responders (58%) and in 5 of 7 SWOG responders (71%) who were Stage III or IV at baseline. In the combined studies, mean hemoglobin concentration improved from 9.0 g/dL at baseline to 11.8 g/dL at the time of response in a subgroup of anemic patients. Similarly, average platelet count improved from 63,500/mm 3 to 103,300/mm 3 at the time of response in a subgroup of patients who were thrombocytopenic at baseline.
Fludarabine Phosphate for Injection, USP is indicated 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 regimen. The safety and effectiveness of Fludarabine Phosphate for Injection, USP in previously untreated or non-refractory patients with CLL have not been established.
Fludarabine phosphate for injection is contraindicated in those patients who are hypersensitive to this drug or its components.
(See BOXED WARNINGS. )
There are clear dose dependent toxic effects seen with fludarabine phosphate for injection. Dose levels approximately 4 times greater (96 mg/m 2 /day for 5 to 7 days) than that recommended for CLL (25 mg/m 2 /day for 5 days) were associated with a syndrome characterized by delayed blindness, coma and death. Symptoms appeared from 21 to 60 days following the last dose. Thirteen of 36 patients (36%) who received fludarabine phosphate for injection at high doses (96 mg/m 2 /day for 5 to 7 days) developed this severe neurotoxicity. Similar severe central nervous system toxicity, including coma, seizures, agitation and confusion, has been reported in patients treated at doses in the range of the dose recommended for chronic lymphocytic leukemia.
In postmarketing experience neurotoxicity has been reported to occur either earlier or later than in clinical trials (range 7 to 225 days).
The effect of chronic administration of fludarabine phosphate for injection on the central nervous system is unknown; however, patients have received the recommended dose for up to 15 courses of therapy.
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