BIIB021

BIIB021 is a selective inhibitor of Hsp90 with Ki and EC50 values of 1.7 nM and 38 nM, respectively.[1]
HSP90 (heat shock protein 90) is widely expressed as a molecular chaperone. It plays a major role in the folding and stabilization of cellular proteins. HSP90 protects client proteins from degradation and maintains them in an active conformation. Many clients of HSP90 are transcription factors or protein kinases such as: Bcr-Abl, tyrosine kinases, EGFR family members, IGF1-R, c-Met, steroid hormone receptors, p53, Mdm2 and telomerase. In a variety of cancers, overexpressed hsp90 has been found. Hsp90 also play an important role in maintaining the transformed phenotype of cancer cells so. Hsp 90 is one attractive target for cancer therapy.[2]
BIIB021 competitive binds in the ATP-binding pocket and inhibits Hsp90 chaperone function, and lead to client protein degradation, cell death and tumor growth inhibition. BIIB021 leads to degradation of HER-2 which is an Hsp90 client protein. BIIB021 can also the growth of a variety of cancer cell lines in cell proliferation assays. In MCF-7 cells, BIIB021 leaded to HER-2 degradation with the EC50 value of was38 ± 10 nmol/L. BIIB021 inhibit the cell proliferation with IC50 values of 0.06 μ mol/L in N87 cells, 0.31μ mol/L in MCF-7 cells and 0.14 μ mol/L in BT474 cells. In MCF-7 cells, BIIB021 significantly reduced the phosphorylation levels of HER-2 at a concentration of 50 nM.[1] BIIB021 selectively inhibited Hodgkin's lymphoma cell viability at nanomolar concentrations but not in lymphocytes from healthy individuals. BIIB021 can increase the susceptibility to NK cell mediated killing by inducing the expression of ligands for the activating NK cell receptor NKG2D on Hodgkin's lymphoma cells.[3] BIIB021 reduced the expression of key radioresponsive proteins, then enhanced the radiosensitivity of HNSCCA cell lines in vitro, increased apoptosis cells and induced G2 arrest.[2]
BIIB021 showed significant activity at doses of 31,62.5, and 125 mg/kg in human in nude mice bearing N87 stomach carcinoma tumors.[1] HSP90 significantly inhibited tumor growth in a xenograft model of Hodgkin's lymphoma.[1]
References:
1.Lundgren K, Zhang H, Brekken J, Huser N, Powell RE, Timple N, Busch DJ, Neely L, Sensintaffar JL, Yang YC et al: BIIB021, an orally available, fully synthetic small-molecule inhibitor of the heat shock protein Hsp90. Mol Cancer Ther 2009, 8(4):921-929.
2.Yin X, Zhang H, Lundgren K, Wilson L, Burrows F, Shores CG: BIIB021, a novel Hsp90 inhibitor, sensitizes head and neck squamous cell carcinoma to radiotherapy. Int J Cancer 2010, 126(5):1216-1225.
3.Boll B, Eltaib F, Reiners KS, von Tresckow B, Tawadros S, Simhadri VR, Burrows FJ, Lundgren K, Hansen HP, Engert A et al: 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, 15(16):5108-5116.

BIIB021, a synthetic Hsp90 inhibitor, induces mutant ataxin-1 degradation through the activation of heat shock factor 1.[Pubmed:27058144]

Neuroscience. 2016 Jul 7;327:20-31.

Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited neurodegenerative disease caused by the expansion of a polyglutamine (polyQ) tract in ataxin-1 (ATXN1). The pathological hallmarks of SCA1 are the loss of cerebellar Purkinje cells and neurons in the brainstem and the presence of nuclear aggregates containing the polyQ-expanded ATXN1 protein. Heat shock protein 90 (Hsp90) inhibitors have been shown to reduce polyQ-induced toxicity. This study was designed to examine the therapeutic effects of BIIB021, a purine-scaffold Hsp90 inhibitor, on the protein homeostasis of polyQ-expanded mutant ATXN1 in a cell culture model of SCA1. Our results demonstrated that BIIB021 activated heat shock factor 1 (HSF1) and suppressed the abnormal accumulation of ATXN1 and its toxicity. The pharmacological degradation of mutant ATXN1 via activated HSF1 was dependent on both the proteasome and autophagy systems. These findings indicate that HSF1 is a key molecule in the regulation of the protein homeostasis of the polyQ-expanded mutant ATXN1 and that Hsp90 has potential as a novel therapeutic target in patients with SCA1.

The heat shock protein 90 inhibitor BIIB021 suppresses the growth of T and natural killer cell lymphomas.[Pubmed:25914683]

Front Microbiol. 2015 Apr 9;6:280.

Epstein-Barr virus (EBV), which infects not only B cells but also T and natural killer (NK) cells, is associated with a variety of lymphoid malignancies. Because EBV-associated T and NK cell lymphomas are refractory and resistant to conventional chemotherapy, there is a continuing need for new effective therapies. EBV-encoded "latent membrane protein 1" (LMP1) is a major oncogene that activates nuclear factor kappa B (NF-kappaB), c-Jun N-terminal kinase (JNK), and phosphatidylinositol 3-kinase signaling pathways, thus promoting cell growth and inhibiting apoptosis. Recently, we screened a library of small-molecule inhibitors and isolated heat shock protein 90 (Hsp90) inhibitors as candidate suppressors of LMP1 expression. In this study, we evaluated the effects of BIIB021, a synthetic Hsp90 inhibitor, against EBV-positive and -negative T and NK lymphoma cell lines. BIIB021 decreased the expression of LMP1 and its downstream signaling proteins, NF-kappaB, JNK, and Akt, in EBV-positive cell lines. Treatment with BIIB021 suppressed proliferation in multiple cell lines, although there was no difference between the EBV-positive and -negative lines. BIIB021 also induced apoptosis and arrested the cell cycle at G1 or G2. Further, it down-regulated the protein levels of CDK1, CDK2, and cyclin D3. Finally, we evaluated the in vivo effects of the drug; BIIB021 inhibited the growth of EBV-positive NK cell lymphomas in a murine xenograft model. These results suggest that BIIB021 has suppressive effects against T and NK lymphoma cells through the induction of apoptosis or a cell cycle arrest. Moreover, BIIB021 might help to suppress EBV-positive T or NK cell lymphomas via the down-regulation of LMP1 expression.

Hsp90 inhibitor, BIIB021, induces apoptosis and autophagy by regulating mTOR-Ulk1 pathway in imatinib-sensitive and -resistant chronic myeloid leukemia cells.[Pubmed:26892093]

Int J Oncol. 2016 Apr;48(4):1710-20.

Development of drug resistance due to BCR-ABL point mutations and the persistence of leukemia initiating cells has become a major obstacle for tyrosine kinase inhibitors (TKIs) in the treatment of chronic myeloid leukemia (CML). The BCR-ABL protein is an important client protein of heat shock protein 90 (Hsp90). BIIB021, an orally available Hsp90 inhibitor, has activity against various cancer cells. However, little is known about the inhibitory effect of BIIB021 on CML cells. We evaluated the inhibitory effects of BIIB021 on K562, K562/G (an imatinib-resistant cell lines), as well as 32D mouse leukemic cells expressing wild-type BCR-ABL (b3a2, 32Dp210) and T315I mutant BCR-ABL (32Dp210-T315I) cells. Our data showed that BIIB021 induced significant growth inhibition and apoptosis that was predominantly mediated by the mitochondrial pathway. BIIB021 also resulted in proteasomal degradation of BCR-ABL proteins. In addition to induction of apoptosis, we report for the first time that BIIB021 induced autophagic response as evidenced by the formation of autophagosome, increased conversion of microtubule-associated protein light chain 3 (LC3)-I to LC3-II, decreased p62 (SQSTM1) protein levels. Further study suggested that Akt-mTOR-Ulk1 signaling pathway was involved in BIIB021-triggered autophagy. Moreover, blocking autophagy using pharmacological inhibitor 3-methyladenine and bafilomycin A1 significantly enhanced cell death and apoptosis induced by BIIB021, indicating the cytoprotective role of autophagy in BIIB021-treated CML cells. Collectively, these data provide possible molecular mechanisms for the antileukemic effect of BIIB021 on imatinib-sensitive and -resistant CML cells and provide new insights into the future application of BIIB021 in the clinical treatment of CML.

Synergistic cytotoxicity of BIIB021 with triptolide through suppression of PI3K/Akt/mTOR and NF-kappaB signal pathways in thyroid carcinoma cells.[Pubmed:27470546]

Biomed Pharmacother. 2016 Oct;83:22-32.

The effec.t of BIIB021, a novel heat shock protein 90 (hsp90) inhibitor, on survival of thyroid carcinoma cells has not been evaluated. In this study, the impact of BIIB021 alone or in combination with the histone acetyltransferase inhibitor triptolide on survival of thyroid carcinoma cells was identified. In 8505C and TPC-1 thyroid carcinoma cells, BIIB021 caused cell death in conjunction with alterations in expression of hsp90 client proteins. Cotreatment of both BIIB021 and triptolide, compared with treatment of BIIB021 alone, decreased cell viability, and increased the percentage of dead cells and cytotoxic activity. All of the combination index values were lower than 1.0, suggesting synergistic activity of BIIB021 with triptolide in induction of cytotoxicity. In treatment of both BIIB021 and triptolide, compared with treatment of BIIB021 alone, the protein levels of total and phospho-p53, and cleaved caspase-3 were elevated, while those of total Akt, phospho-mTOR, phospho-4EBP1, phospho-S6K, phospho-NF-kappaB, survivin, X-linked inhibitor of apoptosis protein (xIAP), cellular inhibitor of apoptosis protein (cIAP) and acetyl. histone H4 were reduced. These results suggest that BIIB021 has a cytotoxic activity accompanied by regulation of hsp90 client proteins in thyroid carcinoma cells. Moreover, the synergism between BIIB021 and triptolide in induction of cytotoxicity is associated with the inhibition of PI3K/Akt/mTOR and NF-kappaB signal pathways, the underexpression of survivin and the activation of DNA damage response in thyroid carcinoma cells.

BIIB021, a novel Hsp90 inhibitor, sensitizes head and neck squamous cell carcinoma to radiotherapy.[Pubmed:19662650]

Int J Cancer. 2010 Mar 1;126(5):1216-25.

Heat shock protein 90 (Hsp90) is a molecular chaperone that promotes the conformational maturation of numerous client proteins, many of which play critical roles in tumor cell growth and survival. The ansamycin-based Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) is currently in Phase III clinical testing. However, 17-AAG is difficult to formulate and associated with dose-limited toxicity issues. A fully synthetic and bioavailable Hsp90 inhibitor, BIIB021, was evaluated for antitumor activity in a variety of head and neck squamous cell carcinoma (HNSCC) cell lines and HNSCC xenograft models, either as a single agent or in combination with fractionated radiation and the results were compared with that of 17-AAG. BIIB021 showed strong antitumor activity, comparable with, and in certain instances, superior to 17-AAG. BIIB021 enhanced the in vitro radiosensitivity of HNSCCA cell lines with a corresponding reduction in the expression of key radioresponsive proteins, increased apoptotic cells and enhance G2 arrest. In xenograft studies, BIIB021 exhibited a strong antitumor effect outperforming 17-AAG, either as a single agent and or in combination with radiation, thereby improved the efficacy of radiation. These results suggest that this synthetic and bioavailable Hsp90 inhibitor affects multiple pathways involved in tumor development and progression in the HNSCC setting and may represent a better strategy for the treatment of HNSCC patients, either as a monotherapy or a radiosensitizer. Furthermore, it also demonstrates the benefits of using preclinical models of chemosensitization to radiotherapy to explore clinically relevant radiation dosing schemes.

BIIB021, an orally available, fully synthetic small-molecule inhibitor of the heat shock protein Hsp90.[Pubmed:19372565]

Mol Cancer Ther. 2009 Apr;8(4):921-9.

Inhibition of heat shock protein 90 (Hsp90) results in the degradation of oncoproteins that drive malignant progression, inducing cell death, making Hsp90 a target of substantial interest for cancer therapy. BIIB021 is a novel, fully synthetic inhibitor of Hsp90 that binds competitively with geldanamycin in the ATP-binding pocket of Hsp90. In tumor cells, BIIB021 induced the degradation of Hsp90 client proteins including HER-2, AKT, and Raf-1 and up-regulated expression of the heat shock proteins Hsp70 and Hsp27. BIIB021 treatment resulted in growth inhibition and cell death in cell lines from a variety of tumor types at nanomolar concentrations. Oral administration of BIIB021 led to the degradation of Hsp90 client proteins measured in tumor tissue and resulted in the inhibition of tumor growth in several human tumor xenograft models. Studies to investigate the antitumor effects of BIIB021 showed activity on both daily and intermittent dosing schedules, providing dose schedule flexibility for clinical studies. Assays measuring the HER-2 protein in tumor tissue and the HER-2 extracellular domain in plasma were used to show interdiction of the Hsp90 pathway and utility as potential biomarkers in clinical trials for BIIB021. Together, these data show that BIIB021 is a promising new oral inhibitor of Hsp90 with antitumor activity in preclinical models.