Changyou Zhou

BGB-283, a Novel RAF Kinase and EGFR Inhibitor, Displays Potent Antitumor Activity in BRAF-Mutated Colorectal Cancers.

Oncogenic BRAF, which drives cell transformation and proliferation, has been detected in approximately 50% of human malignant melanomas and 5% to 15% of colorectal cancers. Despite the remarkable clinical activities achieved by vemurafenib and dabrafenib in treating BRAFV600E metastatic melanoma, their clinical efficacy in BRAFV600E colorectal cancer is far less impressive. Prior studies suggested that feedback activation of EGFR and MAPK signaling upon BRAF inhibition might contribute to the relative unresponsiveness of colorectal cancer to the first-generation BRAF inhibitors. Here, we report characterization of a dual RAF kinase/EGFR inhibitor, BGB-283, which is currently under clinical investigation. In vitro, BGB-283 potently inhibits BRAFV600E-activated ERK phosphorylation and cell proliferation. It demonstrates selective cytotoxicity and preferentially inhibits proliferation of cancer cells harboring BRAFV600E and EGFR mutation/amplification. In BRAFV600E colorectal cancer cell lines, BGB-283 effectively inhibits the reactivation of EGFR and EGFR-mediated cell proliferation. In vivo, BGB-283 treatment leads to dose-dependent tumor growth inhibition accompanied by partial and complete tumor regressions in both cell line-derived and primary human colorectal tumor xenografts bearing BRAFV600E mutation. These findings support BGB-283 as a potent antitumor drug candidate with clinical potential for treating colorectal cancer harboring BRAFV600E mutation. Mol Cancer Ther; 14(10); 2187–97. ©2015 AACR.

Abstract 1653: BGB-290: A highly potent and specific PARP1/2 inhibitor potentiates anti-tumor activity of chemotherapeutics in patient biopsy derived SCLC models

Small cell lung cancer (SCLC) is one of the most aggressive forms of lung cancer with a 5-year survival rate of less than 10%. Despite the initial high response rate to the frontline platinum based chemotherapy, relapse is common and rapid. The clinical activity of PARP inhibitors has shown good correlation with platinum sensitivity in breast and ovarian cancers. Thus, there is good rationale to test PARP inhibitors in SCLC. BGB-290 is a novel PARP-1/2 inhibitor, which is currently under clinical investigation in solid tumors. In this study, we evaluated the in vitro and in vivo activities of BGB-290, and its combination activity with chemotherapies in patient biopsy derived SCLC xenograft models. In the biochemical assays, BGB-290 demonstrated great potency for PARP1/2 (IC50 = 0.83 and 0.11 nM, respectively) and high selectivity over other PARP enzymes. The DNA-trapping activity of BGB-290 was measured in a fluorescence polarization (FP) binding assay. BGB-290 showed potent DNA-trapping activity with IC50 of 13 nM. In the cellular assays, BGB-290 inhibited intracellular PAR formation with an IC50 of 0.24 nM. Tumor cell lines with homologous recombination defects were profoundly sensitive to BGB-290. Oral administration of BGB-290 resulted in time-dependent and dose-dependent inhibition of PARylation in MDA-MB-436 (BRCA1 mutant) breast cancer xenograft, correlating well with the tumor drug concentrations. Compared to olaparib, BGB-290 induced PAR inhibition was more sustained. Consistent with this finding, BGB-290 demonstrated excellent anti-tumor activity in this model, over 10-fold more potent than olaparib. In a panel of 7 SCLC cell lines tested, 3 of them were sensitive to BGB-290. SCLC primary tumor models were established in house using patient biopsy samples obtained from Beijing Cancer Hospital. The anti-tumor activities of BGB-290 as single agent or in combination with etoposide/carboplatin (E/C) were evaluated in 8 SCLC primary tumor models. BGB-290 showed weak single agent activity in these models. Six of the 8 models (75%) were sensitive to E/C treatment, consistent with the clinical response observed in these patients. Addition of BGB-290 as concomitant treatment or maintenance therapy significantly prolonged the response duration in these chemo-sensitive models. In the two chemo-insensitive models, BGB-290 and E/C combo was less effective. Addition of BGB-290 to the chemo regiment was well-tolerated throughout the study. In conclusion, BGB-290 is a potent and selective inhibitor of PARP1/2. It is highly active both in vitro and in vivo in BRCA mutant tumors. BGB-290 has also demonstrated good combination activity with chemotherapeutics in patient biopsy derived SCLC models, supporting further investigation in the clinic. Citation Format: Zhiyu Tang, Ye Liu, Qin Zhen, Bo Ren, Hexiang Wang, Zhenyan Shi, Wenfeng Gong, Yong Liu, Xing Wang, Yajuan Gao, Fenglong Yu, Yiyuan Wu, Bing Jiang, Xuebing Sun, Min Wei, Changyou Zhou, Lusong Luo, Zhengxiang Li, Jiangyong Yu, Jun Zhao, Jie Wang, Lai Wang. BGB-290: A highly potent and specific PARP1/2 inhibitor potentiates anti-tumor activity of chemotherapeutics in patient biopsy derived SCLC models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1653. doi:10.1158/1538-7445.AM2015-1653

Abstract 4698: BET protein inhibitors prevent TKI-induced drug resistance in solid tumors

Acquired drug resistance is one of the major challenges for clinical application of tyrosine kinase inhibitor (TKI) in cancer treatment. TKI-induced drug resistance could develop as a result of adaptive cell reprogramming that leads to pathway feedback activation in the same signaling pathway or parallel pathways or gatekeeper mutations abolishing drug binding. The findings of reversible drug response and lack of genetic mutations in TKI-resistant tumor cells suggest epigenetic basis during resistance development process. Targeting epigenetic modifiers and readers, in particular, the bromodomain and extra-terminal (BET) protein family, has shown promising efficacies against both primary and drug-resistant hematological malignancies via modulating transcription profile and suppressing the MYC oncogene. BGB-3619 is a novel, potent inhibitor of BET family proteins (BRD2, BRD3, BRD4 and BRDT) with IC50 ranging from 20 to 49 nM. It demonstrates superior anti-proliferation activity than iBET762 in multiple leukemia and lymphoma cell lines. In this study, we investigated the effect of BGB-3619 and iBET762 on solid tumor cells during and after TKI-resistance development. From cell killing assays, BET inhibitors were found to be much more potent to TKI-resistant cells (vemurafenib-resistant A375, HT29, SK-MEL-5, cells and erlotinib-resistant HCC827 cells) than their parental cells. Notably, long-term colony formation assays showed that combination of low dose BET inhibitors and TKI effectively suppressed the expansion of TKI-tolerated cell populations. The enhanced sensitivity of TKI-resistant cells to BET inhibitor was due to strong G1 phase arrest rather than induction of apoptosis. Furthermore, BET inhibitors blocked cell proliferation independent of c-Myc inhibition, suggesting they might affect a broad transcription network and provide favorable epigenetic state to induce cell cycle arrest. Taken together, these findings suggested potential therapeutic activity of BET inhibitor in TKI-resistant solid tumors and a strategy of combining BET inhibitors with TKIs to overcome resistance to targeted cancer therapies. Citation Format: Yuan Zhao, Yiyuan Wu, Hexiang Wang, Bo Ren, Ye Liu, Min Wei, Changyou Zhou, Lusong Luo. BET protein inhibitors prevent TKI-induced drug resistance in solid tumors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4698.

Abstract 1651: BGB-290, a novel PARP inhibitor with unique brain penetration ability, demonstrated strong synergism with temozolomide in subcutaneous and intracranial xenograft models

Temozolomide (TMZ) is a DNA alkylating agent, used for treating several malignancies, including glioblastoma multiforme (GBM) and small cell lung cancer (SCLC) with brain metastasis. PARP inhibition could potentially enhance the cytotoxicity of TMZ by hindering the base excision repair (BER) pathway. BGB-290 is a potent and selective inhibitor of PARP1 and PARP2, which is currently under clinical investigation in solid tumors. BGB-290 has significant brain penetration, making it attractive for combining with TMZ in treating brain tumors or tumors with brain metastasis. In this study, we evaluated the combination effect of BGB-290 and TMZ in cellular assays and in animal models. The in vitro combination effect of BGB-290 and TMZ was evaluated in 7 SCLC and 8 GBM cell lines. BGB-290 demonstrated strong synergism with TMZ in most of those cells lines, lowering EC50 of TMZ by at least 5-fold in 4 out of 7 SCLC cell lines, and 7 out of 8 GBM cell lines. The in vivo combination activity was explored in H209 SCLC xenograft model. TMZ single agent was quite effective in this model. One cycle of treatment resulted in all animals tumor-free. However, resistance occurred quickly during the second cycle. Combination of BGB-290 and TMZ significantly delayed resistance without additional toxicity. Tumors remained sensitive to the combination treatment after multiple cycles. In order to investigate whether BGB-290 could overcome the TMZ resistance, TMZ-resistant (TR) H209 tumors were generated by treating the H209 tumors with multiple cycles of TMZ in vivo. The derived H209-TR lines remained sensitive to the combination of BGB-290 and TMZ both in vitro and in vivo, suggesting BGB-290/TMZ combo might work in the TMZ-resistant settings. Approximately 50% of SCLC patients have brain metastases at the time of postmortem examination. BGB-290 showed significant brain penetration in C57 mice. The drug exposure in brain vs. that in plasma was close to 20% after oral administration of BGB-290. Mice with established intracranial H209 xenografts were used to further investigate the combination activity of BGB-290 and TMZ on SCLC in brain. PARylation in brain/tumor tissues was well inhibited at 4 hours after single oral administration of 3 mg/kg of BGB-290. Addition of BGB-290 significantly prolonged animal survival compared to TMZ single agent in this intracranial model. In conclusion, BGB-290 demonstrated strong synergism with TMZ in cellular assays and in SCLC subcutaneous and intracranial xenograft models. When combined with TMZ, BGB-290 can overcome the induced TMZ resistance. Its favorable brain penetration ability warrants further evaluation of BGB-290 in combination with TMZ in GBMs as well as in SCLCs with brain metastasis. Citation Format: Zhiyu Tang, Bin Jiang, Zhenyan Shi, Wenfeng Gong, Yong Liu, Xing Wang, Yajuan Gao, Fenglong Yu, Changyou Zhou, Lusong Luo, Min Wei, Lai Wang. BGB-290, a novel PARP inhibitor with unique brain penetration ability, demonstrated strong synergism with temozolomide in subcutaneous and intracranial xenograft models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1651. doi:10.1158/1538-7445.AM2015-1651

Abstract 4692: BGB-283, a novel RAF kinase and EGFR dual inhibitor, displays potent antitumor activity in B-RAF mutated colorectal cancers

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Oncogenic B-RAF, which drives cell transformation and proliferation, has been detected in approximately 70% of human malignant melanomas and 5-15% of colorectal cancers (CRC). B-RAFV600E mutation, which gives rise to constitutive MAPK signaling, accounts for at least 90% of oncogenic B-RAF mutations. Despite the remarkable clinical activities achieved by vemurafenib and dabrafenib in treating B-RAFV600E metastatic melanoma, their clinical efficacy in B-RAFV600E CRC is far less impressive. Prior studies suggested that feedback activation of EGFR and MAPK signaling upon B-RAF inhibition contributed to the intrinsic resistance of CRC to the first generation B-RAF inhibitors. This report represents the first characterization of a dual RAF kinase/EGFR inhibitor, BGB-283, which is currently under clinical investigations. BGB-283 is a potent and selective pan-RAF and EGFR inhibitor with IC50 ranging from 5 to 47 nM on RAF and EGFR kinases. In vitro, BGB-283 potently inhibits B-RAFV600E-activated ERK phosphorylation and cell proliferation. It demonstrates selective cytotoxicity and preferentially inhibits proliferation of cancer cells harbouring B-RAFV600E and EGFR mutation/amplification. In B-RAFV600E CRC cell lines, BGB-283 effectively inhibits the reactivation of EGFR and achieved sustained inhibition of MAPK pathway. In vivo, BGB-283 is highly efficacious in inhibiting tumor growth accompanied by partial and complete tumor regressions in both BRAFV600E mutant cell derived CRC xenograft models, including HT29, Colo205, WiDr, as well as two primary human CRC xenograft models. In particular, BGB-283 shows compelling efficacy and potent inhibition of EGFR/MAPK signaling in WiDr xenograft model where EGFR reactivation occurs upon B-RAF inhibition. These findings support BGB-283 as a potent antitumor drug candidate with clinical potential for treating CRC harboring B-RAFV600E mutation. Citation Format: Zhiyu Tang, Xi Yuan, Rong Du, Shing-Hu Cheung, Guoliang Zhang, Jing Wei, Yuan Zhao, Yingcai Feng, Yi Zhang, Yunguang Du, Xiaoxia Hu, Wenfeng Gong, Yong Liu, Yajuan Gao, Rui Hao, Jiafu Ji, Lianhai Zhang, Shuangxi Li, David Sutton, Min Wei, Changyou Zhou, Lai Wang, Lusong Luo. BGB-283, a novel RAF kinase and EGFR dual inhibitor, displays potent antitumor activity in B-RAF mutated colorectal cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4692. doi:10.1158/1538-7445.AM2015-4692

Abstract 669: BGB-283 effectively enhances MEK inhibitor induced tumor suppression in RAS mutant cancers

Mutation in K-RAS, which drives constitutive activation of the mitogen-activated protein kinase (MAPK) signaling pathway, is one of the most frequent genetic alterations in human cancers. Pharmacological targeting RAS mutants directly is extremely challenging and targeted inhibition of K-RAS downstream effector MEK has shown limited clinical activity in suppressing the progression of K-RAS mutant tumors. The reduced sensitivity of K-RAS-mutated cancer cells to MEK inhibitors (MEKi) is associated with feedback phosphorylation of MEK and rebound of phosphorylated ERK levels after prolonged treatment. A synthetic lethal screen provided the rational of targeting both RAF1 and MEK in K-RAS mutated cancers. In this study, we investigated whether combining BGB-283, a potent inhibitor to RAF dimers, and a series of MEKi could achieve better therapeutic effect of the latter. We confirmed that selumetinib (AZD6244) induced strong MEK phosphorylation in K-RAS mutated cancer cells. Either knockdown of B-RAF/C-RAF or addition of BGB-283 in the presence of selumetinib potently inhibited RAF-dependent MEK phosphorylation and led to sustained inhibition of ERK activity. Furthermore, BGB-283 and selumetinib showed synergistic effect in inhibiting proliferation of several non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) cell lines harboring RAS mutations. In vivo, combined dosing of BGB-283 and AZD6244 also exhibited enhanced antitumor activity in K-RAS mutant NSCLC and CRC xenograft models compared to monotherapies. Pharmacodynamic (PD) analysis revealed improved inhibition of ERK phosphorylation in dually treated tumors. Together, these findings suggested that combining RAF dimer inhibitor BGB-283 and MEKi could be a promising strategy in treating RAS mutated cancers. Citation Format: Xi Yuan, Zhiyu Tang, Rong Du, Shing-Hu Cheung, Jing Wei, Yuan Zhao, Yunguang Du, Rui Hao, Xiaoxia Hu, Wenfeng Gong, Yong Liu, Yajuan Gao, Min Wei, Changyou Zhou, Lai Wang, Lusong Luo. BGB-283 effectively enhances MEK inhibitor induced tumor suppression in RAS mutant cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 669. doi:10.1158/1538-7445.AM2015-669