Flavopiridol [2-(2-chlorophenyl 5 ,7-dihydroxy-8-[cis-(3-hydroxy-1-methyl-4-piperidinyl)-4H-1-benzopyran-4-one,
hydrochloride] is a semisynthetic flavone with a novel structure compared with
that of polyhydroxylated flavones, such as quercetin and genistein. It is
derived from rohitukine, an alkaloid isolated from the stem bark of Dysoxylum
binectariferum, a plant indigenous to India. Originally synthesized and
supplied by Hoechst India Limited, flavopiridol is provided to the Division of
Cancer Treatment and Diagnosis of the National Cancer Institute (NCI) by Aventis
Mechanism of Action
Cell-cycle regulation is dependent on cyclin-dependent kinases (cdks), which
require association with cyclin proteins for activation. Flavopiridol was the
first compound with the potent ability to disrupt cell-cycle progression by
inhibition of regulatory phosphorylations to be considered for clinical
Flavopiridol inhibits several cellular kinases and has demonstrated
cytostatic and cytotoxic activity in vitro and in vivo in numerous human tumor
cell lines and xenograft models (including human breast, prostate, and lung
carcinoma) at clinically achievable concentrations.[1,4] Flavopiridol is capable
of disrupting progression of cells through the cell cycle at the G1/S and G2/M
transitions.[1,5,7] The direct inhibition of cdks 1, 2, and 4 via competitive
inhibition of adenosine triphosphate binding by flavopiridol has been
demonstrated.[5,7,9] Flavopiridol also inhibits cdk7/cyclin H, thus preventing
the phosphorylation and subsequent activation of several cdks[6,8] and
down-regulates cyclin D1, the cyclin associated with cdks 4 and 6.
Flavopiridol-induced G1 arrest may be related to inhibition of cdk 2 and 4
activity, as well as diminution of cyclin D levels; G2/M arrest may be due in
part to inhibition of cdk1 activity. Cdk4 and 2 kinase activities, as well as
cyclins D, E, and A protein levels, are diminished following flavopiridol
exposure in a number of in vitro models. In MCF-7 cells, flavopiridol-induced
G1/S arrest is associated with the loss of cdk4 and 2 activity and reduced
cyclin D levels preceded by hypophosphorylation of Rb protein. The flavopiridol-induced
decline in cyclin D1 is an early, specific event, due in part to the
transcriptional repression of the cyclin D1 promoter. Similarly, in
cdk4-deficient MCF-10A breast epithelial cells, flavopiridol-induced G1 arrest
coincided with Rb dephosphorylation and dose-dependent inhibition of cdk6-kinase
activity associated with the loss of cyclin D1 expression.
The efficacy of flavopiridol is not based solely on cell cycle arrest, since
this agent induces death in noncycling A549 lung cancer cells by a process that
depends on RNA and protein synthesis. Parker and co-investigators
observed apoptosis in SUDHL-4 leukemia cells without evidence of cell-cycle
arrest, suggesting that the antiproliferative effects can be separated from the
proapoptotic activity of this agent.
Regulation of gene expression is another potential mechanism of action for
flavopiridol. In human monocytes, flavopiridol causes down-regulation of
vascular endothelial growth factor (VEGF) messenger (m)RNA and protein
expression induced by hypoxia. Flavopiridol does not affect hypoxia-induced
transcriptional activation of VEGF but significantly decreases the VEGF mRNA
half-life, suggesting that flavopiridol may have antiangiogenic activity.
Flavopiridol also inhibits the positive transcription elongation factor, which
is a protein kinase composed of cdk9 and a cyclin subunit (cyclin T1 or cyclin
T2) and controls the elongation phase of transcription by RNA polymerase
II. The IC50 of flavopiridol is directly related to the concentration of the
positive transcription elongation factor. (It is not known if the
antiproliferative effects of flavopiridol are due to inhibition of the positive
transcription elongation factor or other cyclin-dependent kinases). A
comprehensive review of the mechanisms of action of flavopiridol was recently
Flavopiridol should exert cytostatic activity because of the pivotal role of
the cdks in the cell division cycle. Evidence demonstrating its cytostatic
activity includes the finding that it inhibits the growth of a broad spectrum of
human tumor cell lines in vitro. In the NCI tumor cell line panel, flavopiridol
had significant inhibitory activity against all of the more than 60 human tumor
cell lines with no clear selectivity for tumor type. IC50 values ranged from
approximately 50 to 200 nM, similar to concentrations required to inhibit
cdks. Flavopiridol-induced growth inhibition seems to be independent of tumor Rb,
cyclin D1, p16, and p53 status.[19,21]
Administration of flavopiridol after or concomitant with antineoplastic
agents, including mitomycin C (Mutamycin), paclitaxel, gemcitabine (Gemzar),
SN-38 (the active metabolite of CPT-11), imatinib mesylate (Gleevec), and
doxorubicin can promote chemotherapy-induced apoptosis.[22-29] Recent reports
suggest a marked increase in apoptosis when differentiating agents such as
phorbol 12-myristate 13-acetate (PMA), suberoylanilide hydroxamic acid (SAHA),
and depsipeptide are combined with flavopiridol.[30-32] Cytotoxic synergy was
more pronounced when non-small-cell lung cancer (NSCLC) A549 cells were
exposed to flavopiridol after rather than before or concomitant with paclitaxel,
cytarabine, topotecan (Hycamtin), doxorubicin, and etoposide.
NCI-sponsored clinical trials of flavopiridol were initiated in 1994.
Preclinical data suggested that prolonged exposure was necessary to achieve
maximal antitumor effect. Two phase I trials used a 72-hour infusion
every-2-weeks schedule. In a trial at the NCI, diarrhea was dose-limiting, and
the maximum tolerated dose was 50 mg/m²/24h ´ 3. Aggressive prophylaxis of
diarrhea allowed for further dose escalation to a maximum tolerated dose of
78 mg/m²/24h ´ 3, with dose-limiting hypotension seen at higher doses.
Anorexia and asthenia were additional major toxicities. Mean steady state plasma
flavopiridol concentrations achieved at the maximum tolerated doses were 271 nM
(range: 174-2,943 nM) and 344 nM (range: 130-1557 nM), respectively, with
postinfusion peaks suggestive of enterohepatic recirculation.
Diarrhea was also dose limiting in a trial using the same schedule conducted
at the University of Wisconsin.[35,36] The maximum tolerated dose was 40
mg/m²/24h ´ 3; nausea, vomiting, and orthostatic hypotension occurred at the
maximum tolerated dose. In this trial, a steady state concentration of 415 nM
was achieved at the maximum tolerated does. Antitumor activity against renal
cell carcinoma, colon carcinoma, non-Hodgkin lymphoma, and gastric carcinoma (a
prolonged complete response) was seen in these studies.
Results of four single-agent flavopiridol studies incorporating a continuous
infusion 50 mg/m²/24h ´ 3 every 14 days in patients with renal cell, gastric,
colon, and non-small- cell lung carcinoma confirmed an adverse event profile
dominated by diarrhea, nausea, vomiting, and asthenia.[37-40] In addition, 19 of
89 patients (21%) experienced venous thromboses, including 12 at the central
venous catheter site. Two patients experienced transient ischemic attacks, and
one, a myocardial infarction. Two complete responses in patients with renal cell
cancer were the only objective responses reported in these trials.
Additional schedules of administration are being pursued because of the
disappointing degree of antitumor activity achieved with the 72-hour schedule
and because of additional preclinical data that suggested higher plasma
concentrations of flavopiridol may be necessary to obtain tumoricidal
activity. NCI investigators followed their original phase I infusional study
with an exploration of daily 1-hour infusions for 1 to 5 days every 21 days.
They defined maximum tolerated doses of 37.5, 50, and 62.5 mg/m²/d for 5-, 3-,
and 1-day administrations, respectively, and documented median peak plasma
concentrations of 1.7, 3.2, and 3.8 µM with these schedules.[42,43] Neutropenia
was the primary dose-limiting toxicity, but diarrhea and a proinflammatory
syndrome of anorexia, tumor pain, fever, and asthenia were also prominent. Five
patients (9%) experienced thrombotic events (three lower-extremity deep-vein
thromboses and two catheter-related thromboses).
Investigators at the National Cancer Center East in Japan determined that 80
mg/m² was tolerable on a weekly 24-hour infusion schedule and achieved a mean
Cmax of 718 nM.
1. Kaur G, Stetler-Stevenson M, Sebers S, et al: Growth inhibition with
reversible cell cycle arrest of carcinoma cells by flavone L86-8275. J Natl
Cancer Inst 84:1736-40, 1992.
2. Naik RG, Kattige SL, Bhat SV, et al: An anti-inflammatory cum
immunomodulatory piperidinylbenzopyranone from Dysoxylum binectariferum:
isolation, structure and total synthesis. Tetrahedron 44:2081-2086, 1988.
3. Sherr CJ: Cancer cell cycles. Science 274:1672-1677, 1996.
4. Bible KC, Kaufmann SH: Flavopiridol: a cytotoxic flavone that induces cell
death in noncycling A549 human lung carcinoma cells. Cancer Res 56:4856-4861,
5. De Azevedo WF Jr, Mueller-Dieckmann HJ, Schulze-Gahmen U, et al:
Structural basis for specificity and potency of a flavonoid inhibitor of human
CDK2, a cell cycle kinase. Proc Natl Acad Sci U S A 93:2735-2740, 1996.
6. Worland PJ, Kaur G, Stetler-Stevenson M, et al: Alteration of the
phosphorylation state of p34cdc2 kinase by the flavone L86-8275 in breast
carcinoma cells. Correlation with decreased H1 kinase activity. Biochem
Pharmacol 46:1831-1840, 1993.
7. Carlson BA, Dubay MM, Sausville EA, et al: Flavopiridol induces G1 arrest
with inhibition of cyclin-dependent kinase (CDK) 2 and CDK4 in human breast
carcinoma cells. Cancer Res 56:2973-2978, 1996.
8. Carlson GA, Pearlstein RA, Naik RG, et al: Inhibition of CDK2, CDK4, and
CDK7 by flavopiridol and structural analogs. Proc Am Assoc Cancer Res 37:424,
9. Losiewicz MD, Carlson BA, Kaur G, et al: Potent inhibition of CDC2 kinase
activity by the flavonoid L86-8275. Biochem Biophys Res Commun 201:589-595,
10. Senderowicz AM, Carlson B, Worland PJ: Decreased transcription of cyclin
D1 induced by a cyclin dependent kinase inhibitor, flavopiridol. Proc Am Assoc
Cancer Res 38:A3159, 1997.
11. Carlson B, Lahusen T, Singh S, et al: Down-regulation of cyclin D1 by
transcriptional repression in MCF-7 human breast carcinoma cells induced by
flavopiridol. Cancer Res 59:4634-4641, 1999.
12. Singh SS, Sausville EA, Senderowicz AM: Cyclin D1 and cdk6 are the
targets for flavopiridol-mediated G1 block in MCF10A breast epithelial cell
line. Proc Am Assoc Cancer Res 40:A184, 1999.
13. Parker BW, Kaur G, Nieves-Neira W, et al: Early induction of apoptosis in
hematopoietic cell lines after exposure to flavopiridol. Blood 91:458-1465,
14. Melillo G, Sausville EA, Cloud K, et al: Flavopiridol, a protein kinase
inhibitor, down-regulates hypoxic induction of vascular endothelial growth
factor expression in human monocytes. Cancer Res 59:5433-7, 1999.
15. Chao SH, Fujinaga K, Marion JE, et al: Flavopiridol inhibits P-TEFb and
blocks HIV-1 replication. J Biol Chem 275:28345-28348, 2000.
16. Price DH: P-TEFb, a cyclin-dependent kinase controlling elongation by RNA
polymerase II. Mol Cell Biol 20:2629-2634, 2000.
17. Chao SH, Price DH: Flavopiridol inactivates P-TEFb and blocks most RNA
polymerase II transcription in vivo. J Biol Chem 276:31793-31799, 2001.
18. Sedlacek HH: Mechanisms of action of flavopiridol. Crit Rev Oncol Hematol
19. Schrump DS, Matthews W, Chen GA, et al: Flavopiridol mediates cell cycle
arrest and apoptosis in esophageal cancer cells. Clin Cancer Res 4:2885-2890,
20. Chien M, Astumian M, Liebowitz D, et al: In vitro evaluation of
flavopiridol, a novel cell cycle inhibitor, in bladder cancer. Cancer Chemother
Pharmacol 144:81-87, 1999.
21. Edelman MJ, Gumerlock PH, Mack PC, et al: Flavopiridol (FLAVO) response
does not require wild type RG protein (pRB) in non-small cell lung cancer (NSCLC)
(abstract). Proc Am Soc Clin Oncol 17:A921, 1998.
22. Werner JL, Greaney C, Spriggs D, et al: The enhancement of
chemotherapy-induced apoptosis by flavopiridol (FLAVO) in gastric cancer cells
is sequence-dependent. Proc Am Soc Clin Oncol 16:A1972, 1997.
23. Schwartz GK, Farsi K, Danso D, et al: The protein kinase C (PKC)
inhibitors UCN-01 and flavopiridol (Flavo) significantly enhance the cytotoxic
effect of chemotherapy by promoting apoptosis in gastric and breast cancer
cells. Proc Am Soc Clin Oncol 15:A207, 1996.
24. Schwartz GK, Farsi K, Maslak P, et al: Potentiation of apoptosis by
flavopiridol in mitomycin-C-treated gastric and breast cancer cells. Clin Cancer
Res 3:1467-1472, 1997.
25. Li W, Fan JG, Bertino JR: Flavopiridol enhances doxorubicin-induced
apoptosis in human sarcoma cells lacking Rb protein. Proc Am Assoc Cancer Res
26. Li W, Fan J, Bertino JR: Selective sensitization of retinoblastoma
protein-deficient sarcoma cells to doxorubicin by flavopiridol-mediated
inhibition of cyclin-dependent kinase 2 kinase activity. Cancer Res
27. Motwani M, Delohery TM, Schwartz GK: Sequential dependent enhancement of
caspase activation and apoptosis by flavopiridol on paclitaxel-treated human
gastric and breast cancer cells. Clin Cancer Res 5:1876-1883, 1999.
28. Motwani M, Jung C, Sirotnak FM, et al: Augmentation of apoptosis and
tumor regression by flavopiridol in the presence of CPT-11 in Hct116 colon
cancer monolayers and xenografts. Clin Cancer Res 7:4209-4219, 2001.
29. Yu C, Dai Y, Dent P, et al: The cyclin-dependent kinase inhibitor
flavopiridol interacts synergistically with the Bcr/ABL kinase inhibitor STI571
to induce mitochondrial damage and apoptosis in Bcr/ABL+ human leukemia cells
(K562 and LAMA-84). Proc Am Soc Hematol:A615, 2001.
30. Cartee L, Smith R, Dai Y, et al: Synergistic induction of apoptosis in
human myeloid leukemia cells by phorbol 12-myristate 13-acetate and flavopiridol
proceeds via activation of both the intrinsic and tumor necrosis factor-mediated
extrinsic cell death pathways. Mol Pharmacol 61:1313-1321, 2002.
31. Almenara J, Rosato R, Grant S: Synergistic induction of mitochondrial
damage and apoptosis in human leukemia cells by flavopiridol and the histone
deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA). Leukemia
32. Nguyen DM, Schrump WD, Chen GA, et al: Flavopiridol enhances depsipeptide-mediated
apoptosis in lung and esophageal cancer cells via activation of mitochondrial
death signal pathways. Proc Am Assoc Clin Res:A350, 2002.
33. Bible KC, Kaufmann SH: Cytotoxic synergy between flavopiridol (NSC
649890, L86-8275) and various antineoplastic agents: The importance of sequence
of administration. Cancer Res 57:3375-3380, 1997.
34. Senderowicz AM, Headlee D, Stinson SF, et al: Phase I trial of continuous
infusion flavopiridol, a novel cyclin-dependent kinase inhibitor, in patients
with refractory neoplasms. J Clin Oncol 16:2986-99, 1998.
35. Thomas J, Tutsch K, Arzoomanian R, et al: Phase I clinical and
pharmacokinetic trial of the cyclin-dependent kinase (CDK) inhibitor
flavopiridol (abstract). Proc Am Soc Clin Oncol 17:8084, 1998.
36. Thomas JP, Cleary JF, Bailey HH, et al: Phase I clinical and
pharmacokinetic trial of the cyclin-dependent kinase inhibitor flavopiridol.
Cancer Chemother Pharmacol. In press.
37. Bennett P, Mani S, O’Reilly S, et al: Phase II trial of flavopiridol in
metastatic colorectal cancer: preliminary results (abstract). Proc Am Soc Clin
Oncol 18:1065, 1999.
38. Schwartz GK, Ilson D, Saltz L, et al: Phase II study of the cyclin-dependent
kinase inhibitor flavopiridol administered to patients with advanced gastric
carcinoma. J Clin Oncol 19:1985-1992, 2001.
39. Shapiro GI, Supko JG, Patterson A, et al: A phase II trial of the cyclin-dependent
kinase inhibitor flavopiridol in patients with previously untreated stage IV
non-small cell lung cancer. Clin Cancer Res 7:1590-1599, 2001.
40. Stadler WM, Vogelzang NJ, Amato R, et al: Flavopiridol, a novel cyclin-dependent
kinase inhibitor, in metastatic renal cancer: A University of Chicago Phase II
Consortium study. J Clin Oncol 18:371-375, 2000.
41. Shapiro GI, Koestner DA, Matranga CB, et al: Flavopiridol induces cell
cycle arrest and p53-independent apoptosis in non-small cell lung cancer cell
lines. Clin Cancer Res 5:2925-2938, 1999.
42. Senderowicz AM, Messmann R, Arbuck S, et al: A phase I trial of 1 hour
infusion of flavopiridol (FLA), a novel cyclin-dependent kinase inhibitor, in
patients with advanced neoplasms (abstract). Proc Am Soc Clin Oncol 19:A796,
43. Tan AR, Headlee D, Messmann R: Phase I clinical and pharmacokinetic study
of flavopiridol administered as a daily 1-hour infusion in patients with
advanced neoplasms. J Clin Oncol. In press.
44. Sasaki Y, Sasaki T, Minami H, et al: A phase I pharmacokinetic (PK)-
pharmacodynamic (PD) study of flavopiridol by 24 hours continuous infusion (CI)
repeating every week. Proc Am Soc Oncol 21:A371, 2002.
45. Connors JM, Kouroukis C, Belch A, et al: Flavopiridol for mantle cell
lymphoma: moderate activity and frequent disease stabilization. Proc Am Soc
46. Burdette-Radoux S, Tozer RG, Lohmann R, et al: NCIC CTG phase II study of
flavopiridol in patients with previously untreated metastatic malignant melanoma
(IND 137). Proc Am Soc Clin Oncol 21:A1382, 2002.
47. Schwartz GK, O’Reilly E, Ilson D, et al: Phase I study of the cyclin-dependent
kinase inhibitor flavopiridol in combination with paclitaxel in patients with
advanced solid tumors. J Clin Oncol 20:2157-2170, 2002.
48. Shah MA, Kaubisch A, O’Reilly E, et al: A phase IB clinical trial of
the sequence dependent combination of paclitaxel (P) and cisplatin (C) with the
cyclin dependent kinase (CDK) inhibitor flavopiridol in patients with advanced
solid tumors. Proc Am Assoc Cancer Res:A2917, 2001.
49. Gries J-M, Kasimis B, Schwarzenberger P, et al: Phase I study of HMR1275
(flavopiridol) in non-small cell lung cancer (NCSLC) patients after 24hr IV
administration in combination with paclitaxel and carboplatin). Proc Am Soc Clin
50. Tan AR, Zhai S, Berman AW, et al: Phase I trial of docetaxel followed by
infusional flavopiridol over 72 hours in patients with metastatic breast cancer.
Proc Am Soc Clin Oncol 21:A1955, 2002.
51. Bible KC, Lensing JL, Nelson SA, et al: A Phase 1 trial of flavopiridol
combined with cisplatin in patients with advanced malignancies (abstract). Proc
Am Assoc Clin Res 2749, 2002.
52. Shah MA, Kortmansky J, Gonen M, et al: A phase I/pharmacologic study of
weekly sequential irinotecan (CPT) and flavopiridol (F) (abstract). Proc Am Soc
Clin Oncol 21:373, 2002.