Abstract 11: Novel dual inhibitors of LSD1-HDAC6/8 for treatment of cancer
Authors: Sivanandhan Dhanalakshmi , Rajagopal Sridharan , Nair Sreekala , Gajendran Chandru , Ghosh Dimpy , Nagaraj P , Tantry Subramanyam J. , Dewang Purushottam , Hallur Mahanandeesha S. , Murugan Kannan , C Srinatha K. , Kuntrapaku Damodara , Dilipkumar M , Sharma R , Meghashree S , Kumar Durga Prasanna , Ingle Suraj P. , Zainuddin Mohd , Vinod A B. , Rajagopal Sriram 
Published: August 2019

Introduction: Lysine Specific Demethylase 1 (LSD1) is a flavin adenine dinucleotide (FAD)-dependent amine oxidase that has been reported to be over-expressed in many malignant tumors. 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 leukemia pathogenesis by inhibiting the normal pro-differentiative function of ATRA, paving the way for new combinatorial therapies for AML. Similarly, HDAC isoform selective inhibitors are beginning to be explored as less toxic alternatives to panHDAC inhibitors in select cancers. Further, combined inhibition of LSD1 and HDAC has been shown to be more efficacious in inhibiting multiple cancers. Here, we show that JBI-295, a dual inhibitor targeting both LSD1 and HDAC6/8 shows stronger efficacy without enhancing systemic toxicity, in a subset of AML and JAK-dependent myeloproliferative cancer.

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 was used to assess biomarkers of LSD1 and HDAC inhibition. Alamar blue cytotoxicity assay was used to assess cell proliferation.

Results: Several compounds from this series show strong in vitro potency against LSD1 with more than excellent selectivity against MAOs. JBI-295 one of the lead dual molecules, showed strong LSD1 potency (IC50 of 0.07 μM) and isoform selective HDAC6/8 activity (IC50 of 0.006 and 0.08 µM on HDAC6 and HDAC8, respectively), with about 100 fold selectivity against other HDAC isoforms. JBI-295 showed strong anti-proliferative activity on leukaemia and multiple myeloma cell lines. In cell based and in vivo target engagement studies there was a concomitant increase in CD11b, CD86 and GFI1b and tubulin acetylation levels. JBI-295 was more efficacious in inhibiting the growth of leukemia HEL92.1.7 xenograft by oral administration when compared to IP administration of ACY-1215, a HDAC6 selective inhibitor. Stronger tumor growth inhibition was also observed in melanoma A375 xenograft model as compared to inhibitors with single activity. In addition, JBI-295 showed single agent activity in a syngeneic murine colon cancer model CT26 and also resulted in stronger tumor growth inhibition when combined with anti-PDL1 antibody.

Conclusion: The data obtained demonstrate that dual LSD1-HDAC6/8 inhibitors could serve as novel, effective therapeutic agents for treatment of select subset of cancer. Advanced efficacy and toxicology studies with JBI-295 are in progress.

Citation Format: Dhanalakshmi Sivanandhan, Sridharan Rajagopal, Sreekala Nair, Chandru Gajendran, Dimpy Ghosh, P Nagaraj, Subramanyam J. Tantry, Purushottam Dewang, Mahanandeesha S. Hallur, Kannan Murugan, Srinatha K. C, Damodara Kuntrapaku, M Dilipkumar, R Sharma, S Meghashree, Durga Prasanna Kumar, Suraj P. Ingle, Mohd Zainuddin, A B. Vinod, Sriram Rajagopal. Novel dual inhibitors of LSD1-HDAC6/8 for treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 11.