793PD - Phase 1 study of the PSMA-targeted small-molecule drug conjugate EC1169 in patients with metastatic castrate-resistant prostate cancer (mCRPC)

Date 10 September 2017
Event ESMO 2017 Congress
Session Genitourinary tumours, prostate
Topics Clinical research
Prostate Cancer
Genitourinary Cancers
Personalised/Precision medicine
Basic Scientific Principles
Basic Principles in the Management and Treatment (of cancer)
Presenter Michael Morris
Citation Annals of Oncology (2017) 28 (suppl_5): v269-v294. 10.1093/annonc/mdx370
Authors M. Morris1, N.J. Vogelzang2, O. Sartor3, A. Armour4, M. Groaning5, R. Messmann6, A. Robarts7, D.P. Petrylak8, A. Tolcher9, M.S. Gordon10, H. Babiker11
  • 1Genitourinary Oncology Service, Memorial Sloan-Kettering Cancer Center, 10065 - New York/US
  • 2Medical Oncology, Comprehensive Cancer Centers of Nevada, 89169 - Las Vegas/US
  • 3Oncology, Tulane University, 70112 - New Orleans/US
  • 4Medical, Endocyte, Inc., Indianapolis/US
  • 5Clinical, Endocyte, 46268 - Indianapolis/US
  • 6Medical Oncology, Endocyte, 47906 - West Lafayette/US
  • 7Genitourinary Oncology Service, Memorial Sloan Kettering Cancer Center, New York/US
  • 8Medical Oncology, Yale University School of Medicine Medical Oncology, 06520-8032 - New Haven/US
  • 9Medical Oncology, South Texas Accelerated Research Therapeutics (START), 78229 - San Antonio/US
  • 10Medical Oncology, HonorHealth Research Institute, Scottsdale/US
  • 11Medical Oncology, University of Arizona Comprehensive Cancer Center, 85724 - Tucson/US



Prostate-specific membrane antigen (PSMA) is highly expressed in prostate cancers, but not in most non-prostate normal tissues, making it a potential therapeutic target. EC1169, a PSMA-targeted conjugate of the microtubule inhibitor tubulysin B hydrazide is being studied in a two-part phase 1 dose escalation (A)/expansion (B) study in mCRPC. The utility of the PSMA-targeted companion imaging agent 99mTc-EC0652 is also being evaluated as a patient selection tool. Part A has been completed. We now report the part B data on pts treated to date.


EC1169 is administered as an IV bolus on days 1, 8 every 21 days. The RP2 dose of 6.5 mg/m2 was determined in Part A. Part B pts are treated at the RP2 dose and enrolled in 1 of 2 cohorts: mCRPC taxane naïve (cohort 1, 45 pts) or taxane exposed (cohort 2, 40 pts). Prior to treatment, pts undergo a 99mTc-EC0652 SPECT/CT scan. The primary endpoint of Part B is median radiographic progression-free survival (rPFS). Other study evaluations are OS, PSA, and CTC-based biomarkers.


Thirty-four of a planned 85 pts in Part B have been treated (14 taxane naïve, 20 taxane exposed). Median age is 70 (range: 49-84). Median number of cycles is 3 (range: 1-7). Twenty-six pts (76.5%) reported at least 1 treatment related AE. Most treatment related AEs (TRAEs) are Gr1 and 2; G3 treatment-related constipation occurred in 1 pt. No Grade 4 TRAEs have been reported. No dose reductions due to AEs have occurred. Six of twelve evaluable taxane-exposed pts in Part B had stable disease or better at their first post-baseline scan (9 wks). One pt currently beyond the 18-week scan has achieved durable resolution of his soft tissue disease. Imaging with 99mTc-EC0652 suggests excellent disease localization.


The RP2 dose of EC1169 is 6.5 mg/m2 (D1, 8 every 21 days). EC1169 has been well tolerated in 34 Part B pts at the RP2 dose A PSMA-targeted therapeutic strategy appears viable. There is evidence of anti-tumor activity in both the taxane naïve and taxane exposed pts.

Clinical trial identification


Legal entity responsible for the study

Endocyte, Inc.


Endocyte, Inc


A. Armour, M. Groaning: Employee of Endocyte, owns company stock. R. Messmann: Contractor for Endocyte, owns company stock. All other authors have declared no conflicts of interest.