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Poster display session

3902 - EPI-506 (ralaniten acetate), a novel androgen receptor (AR) N-terminal domain (NTD) inhibitor, in men with metastatic castration-resistant prostate cancer (mCRPC): Phase 1 update on safety, tolerability, pharmacokinetics and efficacy


10 Sep 2017


Poster display session


Clinical Research;  Prostate Cancer


Ulka Vaishampayan


Annals of Oncology (2017) 28 (suppl_5): v269-v294. 10.1093/annonc/mdx370


U. Vaishampayan1, R.B. Montgomery2, M.S. Gordon3, D.C. Smith4, K. Barber5, A. de Haas-Amatsaleh6, N. Thapar7, C. Chandhasin8, F. Perabo6, K.N. Chi9

Author affiliations

  • 1 Oncology, Karmanos Cancer Institute, 48201-2013 - Detroit/US
  • 2 Genitourinary Medical Oncology, University of Washington, Seattle/US
  • 3 Medical Oncology, HonorHealth Research Institute, Scottsdale/US
  • 4 Medical Oncology, University of Michigan, Ann Arbor/US
  • 5 Clinical Operations, ESSA Pharmaceuticals Corp., 77030 - Houston/US
  • 6 Medical, ESSA Pharmaceuticals Corp., 77030 - Houston/US
  • 7 Clinical Pharmacology, ESSA Pharmaceuticals Corp., 77030 - Houston/US
  • 8 Medical & Scientific Affairs, ESSA Pharmaceuticals Corp., 77030 - Houston/US
  • 9 Experimental Therapeutics, BC Cancer Agency, Vancouver/CA


Abstract 3902


EPI-506 (ralaniten acetate) is being studied in a Phase 1/2 study as a first-in-class transcription inhibitor of the AR NTD.


Open-label, single-arm, Phase 1/2 study evaluating EPI-506 administered orally. The Phase 1 is a modified 3 + 3 design to establish safety, tolerability, pharmacokinetics (PK), maximum-tolerated-dose (MTD) and the recommended phase 2 dose (RP2D) of EPI-506. Anti-tumor activity is evaluated by PSA and imaging. Inclusion criteria include: mCRPC with progression after > =1 line of hormonal therapy or chemotherapy, failure to treatment with enzalutamide and/or abiraterone.


Twenty-one patients (pts) have been enrolled in the dose escalation phase over 6 dose levels (80 - 2,400 mg). Median age was 72 (range 58-87). Prior treatments included enzalutamide only (N = 9), abiraterone only (N = 3) or both (N = 9). Eight pts also had prior chemotherapy. Twelve pts discontinued due to disease progression and 2 pts due to adverse events (AEs): Grade 4 elevated amylase (probably related; at 640mg) and Grade 4 gastrointestinal bleeding (unrelated). Median exposure was 87 days at cut-off (range 21-418). Most frequently reported treatment emergent AEs were diarrhea (N = 8), nausea (N = 6), and pain in extremities (N = 5). One possibly related Grade 3 AE (AST elevation) was observed at 1280 mg. PK data demonstrate a dose-proportional profile for Cmax and AUC together with a positive food effect above 640 mg. Three of 21 evaluable pts demonstrated PSA declines ranging from 4 – 29%, and one pt with unchanged PSA at doses >1,280 mg. Three pts have had prolonged treatment (median of 286 days; range 219 – not reached), after intrapatient dose escalation. The study is currently enrolling pts with a total dose of 3,600 mg in both a QD and a BID dosing schedule.


EPI-506 is well-tolerated with an acceptable safety profile. PK indicates dose-proportionality. PSA declines and stable disease have been observed at higher dose cohorts in this ongoing study. This study is the first to evaluate targeting the AR NTD, a region critical for transcriptional function of all known AR species.

Clinical trial identification


Legal entity responsible for the study

ESSA Pharmaceuticals


ESSA Pharmaceuticals


U. Vaishampayan, M.S. Gordon, D.C. Smith: ESSA Pharmaceuticals Corp. (Research funding) R.B. Montgomery, K.N. Chi: ESSA Pharmaceuticals Corp. (Scientific advisory board; Honoraria received; Research funding). K. Barber, F. Perabo, N. Thapar, C. Chandhasin: ESSA Pharmaceuticals Corp. (Employed, Ownership interest). A. de Haas-Amatsaleh: ESSA Pharmaceuticals Corp. (Consultant).

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