Flavopiridol, Fludarabine and Rituximab (FFR): An Active Regimen in Indolent B-Cell Lymphoproliferative Disorders and Mantle Cell Lymphoma.
Authors: Lin Thomas S. , Fischer Beth , Blum Kristie A. , Porcu Pierluigi , Kraut Eric H. , Baiocchi Robert A. , Moran Mollie E. , Mitchell Sarah , Grever Michael R. , Byrd John C. 
Published: April 2020

Abstract
Background: The cyclin-dependent kinase inhibitor flavopiridol (alvocidib) induces p53-independent apoptosis and may be able to eliminate tumor cells resistant to fludarabine and rituximab.
Study Design and Treatment: We report final results of a phase I dose escalation study of flavopiridol in combination with fludarabine and rituximab (FFR) in patients (pts) with mantle cell lymphoma (MCL), indolent B-cell non-Hodgkin’s lymphoma (B-NHL) and chronic lymphocytic leukemia (CLL). Pts had ANC 3 1500, hemoglobin 3 9.0, platelets 3 100,000, adequate organ function, and ECOG performance status 0–2, and provided informed consent. Pts received fludarabine 25 mg/m2 IV on day 1–5 and rituximab 375 mg/m2 on day 1 every 28 days for up to 6 cycles. Flavopiridol was administered 50 mg/m2 by 1-hr IV bolus on day 1 (cohort 1, n=15) or day 1 and 2 (cohort 2, n=6) of each cycle. Based on promising results with a novel single agent dosing schedule in CLL, the study was amended to give flavopiridol by 30-min IV bolus followed by 4-hr IV infusion at a dose of 20 mg/m2 + 20 mg/m2 (cohort 3, n=3) or 30 mg/m2 + 30 mg/m2 (cohort 4, n=14) beginning with cycle 2. Pts were placed on prophylactic Bactrim and Valtrex. Growth factor support was allowed in cohorts 3 and 4.
Results: Thirty-eight pts were enrolled. Median age was 62 years (range, 38–81), and 22 pts were male (58%). Pts had CLL (11), MCL (10), follicular (FL, 9), small lymphocytic (3), marginal zone (4) or lymphoplasmacytic lymphoma (1). Sixteen pts had received 1 or 2 prior therapies; 22 pts were previously untreated. Two of 6 pts in cohort 2 developed dose limiting toxicity; 1 pt developed grade 3 confusion and grade 3 seizures, and 1 pt developed nausea and diarrhea resulting in grade 3 acute renal failure. Fifteen pts were enrolled in cohort 1 and 14 pts were enrolled in cohort 4, to better define toxicity and efficacy. Pts received a median of 4 cycles (range 1–6), and 16 of 38 pts completed all 6 planned cycles. Cytopenias (10), fatigue (3), fever (2) and progression (2) were the most common reasons for early discontinuation of therapy. Response was graded by NCI 96 criteria (CLL) or IWG criteria (NHL). Overall response rate (ORR) was 82% (CR 50%, CRu 5%, PR 26%). Median progression-free survival (PFS) of responders was 25.5 months. ORR (82% vs. 81%), CR (50% vs. 50%) and median PFS (25.7 vs. 25.1 months) were similar for previously untreated and relapsed pts. Thirteen pts remain in remission with a median PFS of 33.5 months (range, 17.5–59.5), and 3 other pts died of unrelated causes. Eight of 10 MCL pts (median age 68, range 62–81) responded (7 CR, 1 PR). Two responders with blastoid variant MCL relapsed within 1 year, but median PFS of the other 6 responding MCL pts was 33.5 months. All 9 FL pts responded (5 CR, 2 CRu, 2 PR) with a median PFS of 25.1 months (range, 4.0–46.3).
Conclusions: FFR exhibited significant clinical activity in indolent B-NHL, MCL and CLL. FFR was effective in both relapsed and previously untreated pts and showed promising clinical activity in older MCL pts. Changing from 1-hr IV bolus dosing to 30- min IV bolus followed by 4-hr IV infusion did not improve the response rate, suggesting that 1-hr IV bolus dosing may be effective when flavopiridol is given as part of combination chemotherapy. This regimen warrants further study.