"The U.S. Food and Drug Administration today expanded the approved use of Imbruvica (ibrutinib) to treat patients with chronic lymphocytic leukemia (CLL) who carry a deletion in chromosome 17 (17p deletion), which is associated with poor responses"...
Mechanism of Action
Fludarabine phosphate (2F-ara-AMP) is a synthetic purine nucleotide antimetabolite agent. Upon administration, 2F-ara-AMP is rapidly dephosphorylated in the plasma to 2F-ara-A, which then enters into the cell. Intracellularly, 2F-ara-A is converted to the 5'-triphosphate, 2-fluoro-ara-ATP (2F-ara-ATP). 2F-ara-ATP competes with deoxyadenosine triphosphate for incorporation into DNA. Once incorporated into DNA, 2F-ara-ATP functions as a DNA chain terminator, inhibits DNA polymerase alpha, gamma, and delta, and inhibits ribonucleoside diphosphate reductase. 2F-ara-A also inhibits DNA primase and DNA ligase I. The mechanism of action of this antimetabolite is not completely characterized and may be multi-faceted.
In a randomized, uncontrolled, open-label, parallel study, patients with B-cell CLL were administered a single dose of Oforta™ 40 mg/m2 (n = 42) or intravenous fludarabine phosphate 25 mg/m (n=14). The maximum increase in the baseline-corrected mean change in QTcI (individual-corrected QT interval) following treatment with Oforta™ (fludarabine phosphate tablets) was less than 10 milliseconds.
Studies with the intravenous product have demonstrated that fludarabine phosphate is converted to the active metabolite, 2F-ara-A. Clinical pharmacology studies have focused on 2F-ara-A pharmacokinetics.
Following administration of the intravenous product, systemic plasma clearance of 2F-ara-A is approximately 117 mL/min to 145 mL/min. After five daily 30 minute intravenous infusions of 25 mg 2F-ara- AMP/m2 to cancer patients, trough concentrations of 2F-ara-A increased by a factor of about 2. The terminal half-life of 2F-ara-A was approximately 20 hours. Plasma protein binding of 2F-ara-A was approximately 19% to 29%. A correlation was noted between the degree of absolute granulocyte count nadir and increased area under the concentration x time curve (AUC).
2F-ara-A exhibits dose proportional increases in AUC and Cmax after single oral doses of 50 mg, 70 mg or 90 mg of 2F-ara-AMP. Cmax of 2F-ara-A occurs 1 hour to 2 hours after single or multiple oral doses and is approximately 20 % to 30 % of the maximum plasma concentrations produced at the end of a 30 minute intravenous infusion of the same dose. The absolute oral bioavailability of 2F-ara-A is 50 - 65% following single and repeated doses of Oforta™ (fludarabine phosphate tablets) . Similar systemic exposure (AUC) was observed after a single 40 mg/m Oforta™ and a single 25 mg/m2 fludarabine phosphate intravenous dose. The terminal half-life of 2F-ara-A was similar to that following intravenous administration; approximately 20 hours. The Cmax, AUC and terminal half-life of 2F-ara-A are unaffected when administered with a high fat meal, although Tmax is slightly delayed from 1.3 hours to 2.2 hours.
Following intravenous administration, renal clearance of 2F-ara-A represents approximately 40% of the total body clearance of fludarabine phosphate, and total body clearance is inversely correlated with serum creatinine and creatinine clearance. In two patients with median creatinine clearance of 22 mL/min/1.73 m2, 2F-ara-A clearance was reduced by 56%. Dosage adjustment based on creatinine clearance is recommended as follows:
Reduce dose by 20% in patients with mild to moderate renal impairment (creatinine clearance 30 to 70 mL/min/1.73 m2). [See WARNINGS AND PRECAUTIONS]
Reduce dose by 50% in patients with severe renal impairment (creatinine clearance < 30 mL/min/1.73 m2). [See WARNINGS AND PRECAUTIONS]
Study 1, a single-arm, open-label study of Oforta™ (fludarabine phosphate tablets) was conducted in 78 adult patients with CLL refractory to at least one prior standard alkylating-agent containing regimen. In this multicenter study patients were treated with Oforta™ (fludarabine phosphate tablets) at a dose of 40 mg/m daily for 5 days every 28 days. The patient population median age was 64.5 years and consisted of 72% males and 28% females. Ninety-nine percent of the patients were Caucasian. The Rai stage for patients entering the study was: Stage 0 (3.9%), Stage I (20.5%), Stage II (32.1%), Stage III (11.5%), and Stage IV (32.1%). The mean number of treatment cycles was 5.1 with a mean daily dose of Oforta™ (fludarabine phosphate tablets) of 38 mg/m2. The overall objective response, according to standardized response criteria developed by the National Cancer Institute CLL Working Group (NCI criteria), was 51%, including 18% complete responses and 33% partial responses. The overall response rate, according to standardized criteria developed by the International Workshop on CLL (IWCLL criteria), was 46%, including 21% complete responses and 26% partial responses. Data on duration of response was not collected.
In Study 2, a supportive single-arm, open-label study, Oforta™ (fludarabine phosphate tablets) was administered to 81 previously untreated patients with B-CLL. In this multicenter study each patient was treated with Oforta™ (fludarabine phosphate tablets) at a dose of 40 mg/m2 daily for 5 days every 28 days. The patient population median age was 64.0 years and consisted of 63% males and 37% females. Ninety-nine percent of the patients were Caucasian. The Rai stage for patients entering the study was: Stage 0 (3.7%), Stage I (37.0%), Stage II (37.0%), Stage III (9.9%), and Stage IV (12.3%). The mean number of treatment cycles was 5.9 with a mean daily dose per patient of 71 mg to 74 mg. The overall responses rate, according to NCI criteria, was 80%, including 12% complete responses and 68% partial responses. The overall response rate, according to IWCLL criteria, was 72%, including 37% complete responses and 35% partial responses. The median duration of response was 22.9 months.
Study 3 was a supportive randomized controlled open label study in patients with previously untreated B-CLL that included fludarabine phosphate monotherapy and fludarabine phosphate combination therapy arms. In this study 107 evaluable patients received Oforta™ (fludarabine phosphate tablets) 40mg/m orally daily for 5 days every 28 days. The overall response rate according to modified NCI criteria was 74% and the CR plus nodular PR rate was 41%.
1. Preventing Occupational Exposures to Antineoplastic and Other Hazardous Drugs in Health Care Settings. NIOSH Alert 2004-165.
2. OSHA Technical Manual, TED 1-0.15A, Section VI: Chapter 2. Controlling Occupational Exposure to Hazardous Drugs. OSHA, 1999. http://www.osha.gov/dts/osta/otm/otm_vi/otm_vi_2 .html
3. American Society of Health-System Pharmacists. ASHP guidelines on handling hazardous drugs. Am J Health-Syst Pharm. 2006;63:1172-1193.
4. Polovich, M., White, J. M., & Kelleher, L.O. (eds.) 2005. Chemotherapy and biotherapy guidelines and recommendations for practice (2nd. ed.) Pittsburgh, PA: Oncology Nursing Society.
Last reviewed on RxList: 8/5/2009
This monograph has been modified to include the generic and brand name in many instances.
Additional Oforta Information
Oforta - User Reviews
Oforta User Reviews
Now you can gain knowledge and insight about a drug treatment with Patient Discussions.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Find out what women really need.