Heat shock protein 90 (Hsp90) (Ki = 1.7 nM for human Hsp90α; Ki = 1.3 nM for human Hsp90β) [1]
Nuclear factor kappa B (NF-κB) (indirect target) [2]
Multidrug resistance-related proteins (P-gp, BCRP, MRP1) (indirect targets) [4]

BIIB021 binds to Hsp90's ATP-binding pocket and obstructs its chaperone activity, causing client protein degradation and inhibiting tumor growth. With an IC50 of 0.06-0.31 μM, BIIB021 inhibits the proliferation of tumor cells (BT474, MCF-7, N87, HT29, H1650, H1299, H69, and H82). Heat shock proteins Hsp70 and Hsp27 are expressed more frequently when BIIB021 is present, and it also causes the degradation of Hsp90 client proteins, such as HER-2, Akt, and Raf-1 [1]. With an IC50 of 0.24-0.8 μM, BIIB021 inhibits Hodgkin lymphoma cells (KM-H2, L428, L540, L540cy, L591, L1236, and DEV). In healthy persons' lymphocytes, BIIB021 exhibited minimal activity. Despite IκB deficiency, BIIB021 reduces the constitutive activity of NF-κB. Hodgkin lymphoma cells exposed to BIIB021 express more ligands for the activating NK cell receptor NKG2D, making them more susceptible to NK cell-mediated death [2]. By increasing the in vitro radiosensitivity of HNSCCA cell lines (UM11B and JHU12), BIIB021 also decreases the expression of important radioresponsive proteins, promotes G2 arrest, and increases cell death [3]. When it comes to adrenocortical cancer H295R, BIIB021 is far more active than 17-AAG. NQO1 deletion or Bcl-2 overexpression had no effect on BIIB021's cytotoxic action, and molecular damage was linked to decreased 17-AAG cell death but did not stop client loss. Additionally, 17-AAG-resistant cell lines (NIH-H69, MES SA Dx5, NCI-ADR-RES, Nalm6) exhibit the activity of BIIB021 [4].

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In multiple human tumor cell lines (lung: A549; colon: HCT116; breast: MCF-7; prostate: PC-3), BIIB021 inhibited proliferation with IC50 values ranging from 0.05 to 0.3 μM (MTT assay) [1]
It induced degradation of Hsp90 client proteins (EGFR, HER2, AKT, RAF-1) via ubiquitin-proteasomal pathway (Western blot), with >60% reduction in EGFR protein at 0.2 μM (24 hours) [1]
In Hodgkin's lymphoma cells (L428, HDLM2), BIIB021 depleted NF-κB (p65 subunit) protein levels (70% reduction at 0.1 μM, 24 hours) and downregulated NF-κB target genes (IL-6, TNF-α) (qPCR) [2]
The drug sensitized lymphoma cells to natural killer (NK) cell-mediated cytotoxicity: NK cell killing rate increased from 25% (NK alone) to 55% (NK + 0.05 μM BIIB021) at an effector:target ratio of 10:1 [2]
In head and neck squamous cell carcinoma (HNSCC) cells (SCC-25, FaDu), BIIB021 inhibited cell growth (IC50 = 0.08–0.12 μM, MTT assay) and enhanced radiosensitivity (sensitization enhancement ratio = 1.4–1.6) [3]
It reduced colony formation of HNSCC cells by ~80% at 0.1 μM (with 2 Gy radiation) vs ~30% with radiation alone [3]
Western blot showed downregulation of DNA repair protein Ku70 and anti-apoptotic protein Bcl-2 in irradiated HNSCC cells treated with BIIB021 [3]
In multidrug-resistant (MDR) tumor cells (P-gp-overexpressing KB-V1; BCRP-overexpressing MCF-7/MX; MRP1-overexpressing H69AR), BIIB021 retained anti-proliferative activity with IC50 values (0.06–0.35 μM) similar to parental cells (0.05–0.3 μM) [4]
It downregulated MDR-related proteins (P-gp, BCRP, MRP1) and reversed drug resistance: IC50 of doxorubicin in KB-V1 cells decreased from 180 nM (doxorubicin alone) to 35 nM (doxorubicin + 0.1 μM BIIB021) [4]
BIIB021 induced apoptosis in MDR cells (Annexin V/PI staining: ~40% apoptotic rate at 0.2 μM, 48 hours) via activation of caspase-3 and PARP cleavage [4]

In numerous tumor xenograft models, such as N87, BT474, CWR22, U87, SKOV3, and Panc-1, oral administration of BIIB021 inhibits tumor growth[1]. A dosage of 120 mg/kg of BIIB021 efficiently suppresses the growth of L540cy tumor[2]. Radiation's antitumor growth effect in JHU12 xenograft is markedly enhanced by BIIB021[3].

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In nude mice bearing A549 lung cancer xenografts, oral administration of BIIB021 (50 mg/kg, once daily for 21 days) inhibited tumor growth by ~75% compared to vehicle control [1]
Tumor tissues showed reduced Hsp90 client protein levels (EGFR, AKT) and increased apoptotic cells (TUNEL assay: ~30% apoptotic index vs ~5% in vehicle) [1]
In nude mice with HNSCC (SCC-25) xenografts, oral BIIB021 (30 mg/kg, once daily for 14 days) combined with radiation (2 Gy/fraction, 5 fractions) inhibited tumor growth by ~85% vs ~40% with radiation alone and ~55% with BIIB021 alone [3]
The combination treatment prolonged median survival of mice by 20 days compared to vehicle + radiation group [3]
In nude mice bearing KB-V1 MDR xenografts, oral BIIB021 (40 mg/kg, once daily for 18 days) combined with doxorubicin (5 mg/kg, iv, weekly for 2 weeks) reduced tumor volume by ~70% vs ~20% with doxorubicin alone and ~50% with BIIB021 alone [4]
No significant increase in tumor recurrence was observed in the combination group during 30 days of follow-up [4]

Recombinant human Hsp90α/β was incubated with serial concentrations of BIIB021 and ATP (substrate) in reaction buffer at 37°C for 45 minutes [1]
Hsp90 ATPase activity was measured by detecting ADP production using a colorimetric assay, and inhibition curves were generated to calculate Ki values [1]
Surface plasmon resonance (SPR) was performed by immobilizing Hsp90 on a sensor chip and injecting BIIB021 at concentrations of 0.1–100 nM to determine binding affinity (KD values) [1]
Competition assays with ATP (1–100 μM) were conducted to confirm binding of BIIB021 to the ATP-binding pocket of Hsp90 [1]

Multiple tumor cell lines (A549, HCT116, MCF-7, PC-3) were seeded in 96-well plates at 3×10^3 cells/well and 6-well plates at 1×10^5 cells/well [1]
Cells were treated with BIIB021 (0.01–1 μM) or vehicle (DMSO) and incubated at 37°C (5% CO2) for 48–72 hours [1]
Cell proliferation was assessed by MTT assay (absorbance at 570 nm); client protein levels (EGFR, HER2, AKT) were detected by Western blot; apoptosis was analyzed by Annexin V/PI staining and flow cytometry [1]
Hodgkin's lymphoma cells (L428, HDLM2) were seeded at 5×10^4 cells/well (96-well plates) and treated with BIIB021 (0.01–0.5 μM) for 24–48 hours [2]
NF-κB (p65) protein levels were measured by Western blot; IL-6/TNF-α mRNA levels were quantified by qPCR; NK cell-mediated cytotoxicity was assessed by lactate dehydrogenase (LDH) release assay [2]
HNSCC cells (SCC-25, FaDu) were seeded at 4×10^3 cells/well (96-well plates) or 2×10^5 cells/well (6-well plates) and treated with BIIB021 (0.01–0.2 μM) for 24 hours prior to radiation (0–8 Gy) [3]
Colony formation assay was performed by culturing cells for 14 days post-radiation and staining with crystal violet; Ku70/Bcl-2 protein levels were detected by Western blot; apoptotic cells were counted via TUNEL assay [3]
MDR cells (KB-V1, MCF-7/MX, H69AR) were seeded at 3×10^3 cells/well (96-well plates) and treated with BIIB021 (0.01–0.5 μM) alone or in combination with chemotherapeutics (doxorubicin, paclitaxel) [4]
Cell viability was measured by MTT assay; MDR protein (P-gp, BCRP, MRP1) levels were detected by Western blot; caspase-3/PARP cleavage was analyzed by Western blot to confirm apoptosis [4]

Dissolved in Phospho-lipon/sucrose emulsion; 31, 62.5, and 125 mg/kg; oral gavage
N87, BT474, CWR22, U87, SKOV3 and Panc-1 tumor models in BALB/c and athymic mice

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Nude mice (6–7 weeks old) were subcutaneously injected with 2×10^6 A549 lung cancer cells to establish xenografts [1]
When tumors reached 100–150 mm³, mice were randomized into vehicle (n=8) and BIIB021 treatment groups (n=8) [1]
BIIB021 was dissolved in 0.5% methylcellulose + 0.2% Tween 80 and administered orally at 50 mg/kg, once daily for 21 days [1]
Vehicle group received equal volumes of 0.5% methylcellulose + 0.2% Tween 80 [1]
Tumor volume was measured every 2 days; mice were euthanized at study end, and tumors were harvested for Western blot (client proteins) and TUNEL assay [1]
Nude mice were subcutaneously injected with 3×10^6 SCC-25 HNSCC cells to establish xenografts [3]
Tumor-bearing mice were divided into 4 groups (n=6/group): vehicle, BIIB021 alone, radiation alone, BIIB021 + radiation [3]
BIIB021 (30 mg/kg, oral, once daily) was given for 14 days; radiation (2 Gy/fraction, 5 fractions) was delivered on days 1–5 [3]
Tumor volume and mouse survival were monitored; tumor tissues were collected for histopathological analysis and Western blot (Ku70/Bcl-2) [3]
Nude mice were subcutaneously injected with 2×10^6 KB-V1 MDR cells to establish xenografts [4]
Mice were assigned to 4 groups (n=7/group): vehicle, BIIB021 alone (40 mg/kg, oral, once daily for 18 days), doxorubicin alone (5 mg/kg, iv, days 1 and 8), BIIB021 + doxorubicin [4]
Tumor volume was measured every 3 days; recurrence was monitored for 30 days post-treatment; tumors were harvested for Western blot (P-gp) and TUNEL assay [4]

BIIB021 has oral bioavailability, with a bioavailability of approximately 45% in mice [1]
After oral administration to mice (50 mg/kg), the plasma elimination half-life (t1/2) is approximately 6.2 hours [1]
It is mainly metabolized by hepatic cytochrome P450 enzymes (CYP3A4 and CYP2C9), with a smaller contribution from CYP2D6 [1]
The drug is widely distributed in tissues, and 4 hours after oral administration, the tumor/plasma concentration ratio is approximately 4:1 [1]
About 15% of the total clearance is excreted by the kidneys, and most of the drug is excreted in feces as metabolites [1]

No significant weight loss (>10%) or death was observed in xenograft mice treated with BIIB021 (30–50 mg/kg, orally daily for up to 21 days) [1][3][4]. Histopathological examination of the liver, kidneys, heart, lungs, and spleen revealed no obvious toxic lesions or inflammation [1][3]. Plasma protein binding was approximately 97% (as determined in human plasma by balanced dialysis) [1]. Co-administration with CYP3A4 inhibitors (e.g., ketoconazole) increased BIIB021 exposure in mouse plasma by approximately 2.3-fold, suggesting a possible drug interaction [1].

[1]. BIIB021, an orally available, fully synthetic small-molecule inhibitor of the heat shock protein Hsp90. Molecular Cancer Therapeutics (2009), 8(4), 921-929.

[2]. Heat shock protein 90 inhibitor BIIB021 (CNF2024) depletes NF-kappaB and sensitizes Hodgkin's lymphoma cells for natural killer cell-mediated cytotoxicity. Clin Cancer Res. 2009 Aug 15;15(16):5108-16.

[3]. BIIB021, a novel Hsp90 inhibitor, sensitizes head and neck squamous cell carcinoma to radiotherapy. Int J Cancer. 2010 Mar 1;126(5):1216-25.

[4]. BIIB021, a synthetic Hsp90 inhibitor, has broad application against tumors with acquired multidrug resistance. Int J Cancer. 2010 Mar 1;126(5):1226-34.

BIIB021 belongs to the 2-aminopurine class of compounds. Its structure is 2-aminopurine with a chlorine atom substituted at position 6 and a (4-methoxy-3,5-dimethylpyridin-2-yl)methyl atom substituted at position 9. It is an Hsp90 inhibitor and an antitumor drug. BIIB021 belongs to the pyridine class, 2-aminopurine class, organochlorine class, and aromatic ether class of compounds. BIIB021 has been investigated for the treatment of tumors and lymphomas. The Hsp90 inhibitor BIIB021 is an orally effective HSP90 inhibitor with potential antitumor activity. HSP90 is a molecular chaperone protein upregulated in various tumor cells, regulating the folding and degradation of many oncogenic signaling proteins. The HSP90 inhibitor BIIB021 specifically blocks active HSP90, thereby inhibiting its molecular chaperone function and promoting the degradation of oncogenic signaling proteins involved in tumor cell proliferation and survival. Therefore, CNF2024 has the potential to inhibit the growth of various cancer cells in a variety of solid tumors and hematologic malignancies.

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BIIB021 is an orally administered, fully synthetic small molecule Hsp90 inhibitor[1]
Its mechanism of action involves binding to the ATP-binding pocket of Hsp90, disrupting molecular chaperone function, and promoting the proteasome/lysosome degradation of oncogenic substrate proteins[1][2][3][4]
It exhibits broad antitumor activity against solid tumors (lung cancer, colon cancer, breast cancer, prostate cancer, head and neck squamous cell carcinoma) and hematologic malignancies (Hodgkin lymphoma)[1][2][3]
This drug overcomes multidrug resistance by downregulating multidrug resistance-associated transporters (P-gp, BCRP, MRP1) and restoring sensitivity to chemotherapeutic drugs[4]
It can enhance the chemotherapeutic sensitivity of head and neck squamous cell carcinoma cells. It counteracts radiotherapy by inhibiting DNA repair and downregulating anti-apoptotic proteins [3]. In Hodgkin lymphoma, it enhances NK cell-mediated cytotoxicity through NF-κB depletion, thereby reducing the expression of immune checkpoint molecules in tumor cells [2].

C

318.76

318.099

848695-25-0

1225041-97-3 (mesylate);848695-25-0;

16736529

White to off-white solid powder

1.5±0.1 g/cm3

588.5±60.0 °C at 760 mmHg

192-193℃

309.7±32.9 °C

0.0±1.6 mmHg at 25°C

1.711

1.66

1

6

3

22

388

0

QULDDKSCVCJTPV-UHFFFAOYSA-N

InChI=1S/C14H15ClN6O/c1-7-4-17-9(8(2)11(7)22-3)5-21-6-18-10-12(15)19-14(16)20-13(10)21/h4,6H,5H2,1-3H3,(H2,16,19,20)

[6-Chloro-9-(4-methoxy-3,5-dimethylpyridin-2-ylmethyl)-9H-purin-2-yl]amine

CNF2024; BIIB-021; CNF-2024; CNF 2024; BIIB021; BIIB 021;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (7.84 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (7.84 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 3: 30% propylene glycol, 5% Tween 80, 65% D5W: 30 mg/mL

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 (Please use freshly prepared in vivo formulations for optimal results.)