Abstract 1756: JBI-802, novel dual inhibitor of LSD1-HDAC6 for treatment of cancer
Authors: Sivanandhan Dhanalakshmi , Rajagopal Sridharan , Nair Sreekala , B Basavaprabhu , Dhkar Reshma , Viswakarma Santosh , Siddiqui Amir , Zainuddin Mohd , G Rudresh , Daram Prashanthi , Mohire Sunil , V Krishnakumar 
Published: September 2020

Introduction: Lysine Specific Demethylase 1 (LSD1) is over-expressed in many cancers and down-regulation of LSD1 has been shown to effectively treat cancers by inducing re-expression of aberrantly silenced genes. Studies have shown that LSD1 may contribute to acute myelogenous leukaemia pathogenesis by inhibiting the normal pro-differentiative function of ATRA, paving the way for new combinatorial therapies for AML. In addition, LSD1 inhibition also leads to convertion of ‘cold' tumors to ‘hot' tumors by activating type 1 interferon response. Similarly, HDAC6 inhibition enhances immune response by over-coming immune suppression. Further, combined inhibition of LSD1 and HDAC has been shown to be more efficacious in inhibiting multiple cancers. Here, we show that JBI-802, a dual inhibitor targeting both LSD1 and HDAC6/8 shows stronger efficacy in several cancers, including AML, lymphoma and others and well tolerated at efficacious doses.

Methods: Computational chemistry approaches were used to design LSD1 specific and LSD1-HDAC dual inhibitors. To assess in vitro LSD1 potency, TR-FRET assay was used. For assessing in vitro HDAC activity fluorescence based HDAC6 activity assay was performed. Western blotting and quantitative PCR were used to assess biomarkers of LSD1 and HDAC inhibition. Alamar blue cytotoxicity assay was used to assess cell proliferation. Xenograft and syngeneic models were used to assess in vivo efficacy.

Results: Several compounds from this series show strong in vitro potency against LSD1 with excellent selectivity against MAOs. JBI-802 our lead dual molecule, showed an IC50 of 0.05 μM against LSD1 and isoform selective HDAC6/8 activity (IC50 of 0.011 and 0.098 µM on HDAC6 and HDAC8, respectively), with about 100 fold selectivity against other HDAC isoforms. When assessed in a panel of 25 cell lines, JBI-802 showed strong anti-proliferative activity on select AML, CLL, SCLC, sarcoma and multiple myeloma cell lines. In cell based and in vivo target engagement studies there was significant dose-dependent increase in CD11b, CD86 and GFI1b and tubulin acetylation levels. JBI-802 had a much stronger effect in inhibiting the growth of HEL92.1.7 erythroleukemia xenograft by oral administration when compared to ACY-1215, a HDAC6 selective inhibitor or ORY-1001 an LSD1 selective inhibitor. ED50 of JBI-802 in this model was ~6.25 mg/kg BID. Further, dose-dependent modulation of above mentioned biomarkers and inhibition of c-Myc could be observed in tumors. Stronger tumor growth inhibition was also observed in other haematological cancers models such as CMK-1 (leukemia) and Z-138 (lymphoma). In addition, JBI-802 showed comparable single agent activity to anti-PD-1/PD-L1 mAbs in a syngeneic murine colon cancer model CT26 and resulted in stronger tumor growth inhibition when combined with these antibodies. 14-day dose ranging finding toxicology studies clearly show that the molecule was well tolerated up to 300 mg/kg.

Conclusion: The data obtained to date demonstrate that dual LSD1-HDAC6/8 inhibitors could serve as novel, effective therapeutic agents for treatment of select subset of AML and other cancers. IND-enabling studies are in progress with this inhibitor to be developed as a clinical candidate

Citation Format: Dhanalakshmi Sivanandhan, Sridharan Rajagopal, Sreekala Nair, Basavaprabhu B, Reshma Dhkar, Santosh Viswakarma, Amir Siddiqui, Mohd Zainuddin, Rudresh G, Prashanthi Daram, Sunil Mohire, Krishnakumar V. JBI-802, novel dual inhibitor of LSD1-HDAC6 for treatment of cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1756.