EPI-7386 is a novel N-terminal domain androgen receptor inhibitor for the treatment of prostate cancer

Date 28 September 2019
Event ESMO 2019 Congress
Session Poster Display session 1
Topics Clinical Research
Presenter Ronan Le Moigne
Citation Annals of Oncology (2019) 30 (suppl_5): v159-v193. 10.1093/annonc/mdz244
Authors R. Le Moigne1, C.A. Banuelos2, N.R. Mawji2, T. Tam2, J. Wang2, K. Jian3, R.J. Andersen3, A. Cesano1, M.D. Sadar2, H. Zhou1, P. Virsik1
  • 1Preclinical, ESSA Pharmaceuticals Corp., 77002 - Houston/US
  • 2Department Of Genome Sciences Centre, BC Cancer Agency, V5Z 1L3 - Vancouver/CA
  • 3Department Of Chemistry, University of British Columbia, V6T 1Z1 - Vancouver/CA

Abstract

Background

The androgen receptor (AR) pathway drives most metastatic castration-resistant prostate cancers (mCRPC) even in late stages of the disease. Anti-androgen resistance mechanisms include AR gene amplification, C-terminal ligand-binding domain (LBD) mutations and expression of constitutively-active truncated AR splice variants lacking the LBD (eg. AR-V7). Selective inhibition of the N-terminal domain (NTD) of the AR can inhibit its’ transcriptional activity even in the presence of LBD-driven resistance. A Phase I clinical trial of the first-generation AR NTD inhibitor, EPI-506, demonstrated minor PSA declines in mCRPC patients. EPI-7386 is a more potent and stable NTD inhibitor (Anitens) that is advancing to clinical trials. The compounds’ characteristics and the initial clinical study plans including potential biomarkers will be reviewed.

Methods

Chemical structure activity relationships were developed to increase molecule potency using a wide variety of CRPC models in vivo and in vitro. Similarly, the stability and selectivity of the molecule were characterized with screening and functional assays. Biomarkers were also explored.

Results

EPI-7386 demonstrated a 20 fold improvement in AR-driven cellular potency compared to EPI-002, while being highly stable in human and animal hepatocytes. In vitro proliferation assays demonstrated on-target activity across a panel of prostante cancer cell lines, with activity in AR-V7-driven cellular models. EPI-7386 was able to control tumor growth and induce tumor regressions in several CRPC xenografts, including enzalutamide resistant models. In addition, the combination of enzalutamide with EPI-7386 demonstrated a more robust and more homogeneuous antitumor response. Pharmacodynamic markers specific to NTD inhibitors will be presented.

Conclusions

The next generation aniten compound EPI-7386 is more active and more metabolically stable than EPI-002. It demonstrated potential as single agent in overcoming anti-androgen clinical resistance as well as in combination therapy in earlier stages of the disease. The clinical strategy supporting the development of this new generation of Aniten will be discussed.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

ESSA Pharmaceuticals.

Funding

ESSA Pharmaceuticals.

Disclosure

R. Le Moigne: Full / Part-time employment: ESSA pharma. C.A. Banuelos: Shareholder / Stockholder / Stock options: ESSA pharma. N.R. Mawji: Shareholder / Stockholder / Stock options: ESSA pharma. R.J. Andersen: Research grant / Funding (institution), Shareholder / Stockholder / Stock options, Officer / Board of Directors: ESSA pharma. A. Cesano: Advisory / Consultancy: ESSA pharma; Full / Part-time employment: Nanostring. M.D. Sadar: Speaker Bureau / Expert testimony, Leadership role, Research grant / Funding (institution), Travel / Accommodation / Expenses, Shareholder / Stockholder / Stock options, Officer / Board of Directors: ESSA pharma; Speaker Bureau / Expert testimony: Pfizer. H. Zhou: Shareholder / Stockholder / Stock options, Full / Part-time employment: ESSA pharma. P. Virsik: Shareholder / Stockholder / Stock options, Full / Part-time employment: ESSA pharma. All other authors have declared no conflicts of interest.