Background Signaling through VEGF/VEGFR induces cancer angiogenesis and affects immune cells. An increasing number of studies have recently focused on combining anti-VEGF/VEGFR agents and immune checkpoint inhibitors (ICIs) to treat cancer in preclinical and clinical settings. BD0801 is a humanized rabbit anti-VEGF monoclonal antibody in the clinical development stage. Methods In this study, the anti-cancer activities of BD0801 and its potential synergistic anti-tumor effects when combined with different immunotherapies were assessed by using in vitro assays and in vivo tumor models. Ex vivo studies were conducted to reveal the possible mechanisms of actions (MOA) underlying the tumor microenvironment modification. Results BD0801 showed more potent antitumor activity than bevacizumab, reflected by stronger blockade of VEGF/VEGFR binding and enhanced inhibitory effects on human umbilical vein endothelial cells (HUVECs). BD0801 exhibited dose-dependent tumor growth inhibitory activities in xenograft and murine syngeneic tumor models. Notably, combining BD0801 with either anti-PD-1 or anti-PD-L1 antibodies showed synergistic antitumor efficacy in both lung and colorectal cancer mouse models. Furthermore, the mechanistic studies suggested that the MOA of the antitumor synergy involves improved tumor vasculature normalization and enhanced T-cell mediated immunity, including increased tumor infiltration of CD8+ and CD4+ T cells and reduced double-positive CD8+PD-1+ T cells. Conclusions These data provide a solid rationale for combining antiangiogenic agents with immunotherapy for cancer treatment and support further clinical development of BD0801 in combination with ICIs.

Targeting DNA damage response (DDR) pathway has been proposed as an approach for amplifying tumor-specific replicative lesions. RAD51 plays a central role in the DDR process, and thus represents a promising anti-tumor target. We here report the discovery of a series of next generation RAD51 inhibitors that can prevent RAD51 foci formation. The lead compounds dramatically impaired human cancer cell growth, induced cell cycle arrest in S-phase, and resulted in elevated γH2AX. Furthermore, cancer cells became sensitized to chemotherapy and other DDR inhibitors. Dosed either as a single agent or in combination with cisplatin, the compounds significantly inhibited tumor growth in vivo. By upregulating ATR-CHK1 signaling, the RAD51 inhibitors increased surface PD-L1 levels in various tumor cells, suggesting a potential combination of RAD51 inhibitors with PD-1/PD-L1 blockade. Overall, our findings provide the preclinical rationale to explore RAD51 inhibitors as monotherapy or in combination with chemotherapy, immunotherapy or DDR-targeting therapy in cancer treatment.

The E3 ubiquitin ligase Casitas B-lineage lymphoma b (Cbl-b) is a member of the highly conserved family of Cbl (casitas b-lineage lymphoma) proteins. CBL-b is widely expressed in immune cells and plays as a “gate keeper” to negatively regulate the activation of immune cells. Engagement of TCR/BCR triggers the Cbl-b-mediated ubiquitination and degradation of the key components in TCR axis, such as Vav1 and PLCγ, and consequently attenuates TCR/BCR signal axis which finally results in T/B cells exhaustion. Besides, Cbl-b was reported to negatively regulate the activation of dendritic cells, NK, NKT, and mast cells. Cbl-b KO mice show resistance to tumor transplantation, and the anti-tumor activities depend on the T and NK cells. According to the above observation, Cbl-b emerges as a novel intracellular immune checkpoint target to prevent immune cells from exhaustion and improve the antitumor immunotherapy. Here we identified a series of highly potent Cbl-b inhibitors. The inhibition of Cbl-b protein was evaluated by an in vitro CBL-b/E2-ubiquitin assay. Results showed that our candidates strongly inhibited Cbl-b with IC50s at single-digital nanomolar level, and meanwhile, these compounds displayed over than 10-fold selectivity against c-CBL/E2-ubiquitin, a member of the Cbl family, which was reported to synergistically enhance toxicity caused by Cbl-b. Consistent with the Cbl-b inhibition, these compounds further enhanced activation of Jurkat T cells as well as human PBMCs with dramatical increase of IL-2 or IFNɣ secretion in presence of anti-CD3/CD28, and without any significant cytotoxicity even up to 10 µM concertation. Furthermore, these compounds exhibited the restoring function in exhausted T cells in presence with PEG2 or adenosine treatment. Favorable ADME and bioavailability supported the oral administration. In naïve mice, our inhibitors dose-dependently promoted the cytokine IL-2 and IFNɣ production in serum and spleens following the anti-CD3 challenge. In a syngeneic model, CT26, oral administration of our Cbl-b inhibitor effectively inhibited tumor growth, while completely inhibited tumor growth in combination with an anti-PD1 antibody. Further study demonstrated that the increased lymphocytes infiltration and cytokines release in tumor tissues were observed either in Cbl-b mono or in anti-PD1 combo groups, which correlated well with anti-tumor efficacy. In conclusion, our selective Cbl-b inhibitors demonstrated robust immune activation and anti-tumor activity in vitro and in vivo and showed synergistic activities with immune checkpoint inhibitors, such as anti-PD(L)1. Currently, one of our leading molecules is in IND enabling studies. Citation Format: Feng Zhou, Zhengtao Li, Yajing Liu, Guimei Yang, Wansun Mai, Wenqing Yang, Liting Xue, Ping Chen, Renhong Tang. Identification of the selective CBL-b inhibitors which effectively prevent T cells from exhaustion and demonstrate synergistic anti-tumor activity in combination with an anti-PD1 antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3474.

Malignant ascites (MA) is caused by intraperitoneal spread of solid tumor cells and results in a poor quality of life. Chemotherapy is a common first-line treatment for patients with MA. Taxotere ® (DTX) is widely used in solid tumor therapies. However, the low water solubility and side effects caused by additives in the formulation restrict the clinical application of docetaxel. HT001 is a clinical stage docetaxel micelle developed to overcome the solubility issue with improved safety profiles. To support clinical development and expand clinical application of HT001, this study used in vitro and in vivo approaches to investigate the anti-tumor effects of HT001 when applied as monotherapy or in combination with anti-angiogenic agents. HT001 demonstrated comparable anti-proliferative activities as docetaxel in a broad range of cancer cell lines in vitro. Furthermore, HT001 suppressed tumor growth in a dose-dependent manner in A549, MCF-7, and SKOV-3 xenograft tumor mouse models in vivo. In a hepatocellular carcinoma H22 malignant ascites-bearing mouse model, HT001 presented a dose-dependent inhibition of ascites production, prolonged animal survival, and reduced VEGF levels. When dosed at 20 mg/kg, the HT001-treated group exhibited curative results, with no ascites formation in 80% of mice at the end of the study while all the mice in the vehicle control group succumbed. Similar results were obtained in HT001 treatment of mice bearing malignant ascites produced by human ovarian cancer ES-2 cells. Notably, the combination of HT001 with Endostar not only significantly reduced ascites production but also prolonged survival of H22 ascites-bearing mice. HT001 showed similar PK and tissue distribution profiles as DTX in non-rodent hosts. Collectively, these results demonstrate potent anti-tumor activity of HT001 in multiple solid tumor models or malignant ascites models, and reveal synergistic effects with anti-angiogenic agents, supporting the clinical development and clinical expansion plans for HT001.

Benefits of endocrine therapy in treating hormone receptor (HR)-positive (HR+) BC are well recorded in clinic. However, ~40% to 50% of HR+ patients eventually developed to endocrine resistance and disease relapsed. Fulvestrant, a selective estrogen receptor degrader (SERD) is approved to treat HR+ metastatic breast cancer in patients with disease progression after endocrine therapy. However, due to its poor bioavailability, it is given by intramuscular injection, which makes inconvenience in administration. Additionally, approximately 14% of hormone positive patients with advanced breast cancer are diagnosed with brain metastases, while, at present, there are no FDA-approved systemic therapies for the treatment of breast cancer brain metastases. Therefore, to develop a new generated oral and brain-penetrant SERD to overcome these challenges is believed to be needed. SCR6106, discovered and currently being developed by Simcere, is a novel, potent, orally delivered and non-steroidal SERD that both antagonizes and degrades ERα. SCR6106 showed high potency on inducing ERα protein degradation (DC50=0.29 nM) and anti-proliferation (IC50=0.43 nM) in MCF7 cells. In addition, SCR6106, showed high activities on ERα degradation and anti-proliferation in a panel of ER+ breast cancer cell lines. Meanwhile, ER target genes transcription were evaluated and SCR6106 exhibit strong suppressive phenotype in T-47D. SCR6106 demonstrated more potent than fulvestrant on anti-tumor growth in vivo. In MCF7 xenograft model, SCR6106 at 3 mpk QD induced 113% tumor growth inhibition (TGI), compared to fulvestrant 56.8% TGI at 250 mpk. Compared to fulvestrant, SCR6106 demonstrated stronger ERα degradation and inhibition of ER target genes transcription in tumors, which was consistent with anti-tumor activities. SCR6106 displayed good oral bioavailability in multiple pre-clinical species, which supports its oral administration in human. Significantly, SCR6106 possess a high BBB permeability, the B/P ratio is more than 4 in pre-clinical species. The exposure of SCR6106 observed in mouse brain is much higher than the IC90 value of anti-proliferation (MCF7), and SCR6106 demonstrated anti-tumor activities in a MCF-7 intracranial tumor xenograft model. In conclusion, SCR6106 is a novel, potent and oral SERD, which demonstrated anti-tumor activities in vitro and in vivo. It showed high potential ability to cross the blood-brain barrier, and could be used to treat HR+ patients with brain metastasis. Citation Format: Feng Zhou, Lei Liu, Guimei Yang, Peng Gu, Liting Xue, Wenqing Yang, Ping Chen, Renhong Tang. SCR6106, an oral and brain penetrant SERD demonstrated anti-tumor activities in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1070.