On May 9, 2018 Endocyte, Inc. (Nasdaq:ECYT), a biopharmaceutical company developing targeted therapeutics for personalized cancer treatment, reported The Lancet Oncology publication of data on 30 patients with PSMA-positive metastatic castration-resistant prostate cancer (mCRPC) treated with 177Lu-PSMA-617 (Press release, Endocyte, MAY 9, 2018, View Source [SID1234526367]). Preliminary results of this open-label phase 2 investigator-initiated trial were previously announced at the 2017 ESMO (Free ESMO Whitepaper) Congress and presented by Professor Michael Hofman of the Peter MacCallum Cancer Centre (Melbourne, Australia).

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"This more detailed publication was consistent with or improved from the summary results presented at ESMO (Free ESMO Whitepaper) last fall," said Mike Sherman, president and CEO of Endocyte. "The response rates demonstrated to date are encouraging, especially since no agent has been proven to improve survival in this heavily pre-treated patient population. We look forward to beginning enrollment in our global phase 3 VISION trial of 177Lu-PSMA-617 this quarter."

Mr. Sherman continued, "We also look forward to Professor Hofman presenting additional updates at the American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting in June, with new data from the trial’s expansion to 50 patients. Given the expected immaturity of survival data in the additional 20 patients, our focus will be on the PSA and RECIST response rates."

Updated Data Disclosed in The Lancet Oncology

The journal article published today in The Lancet Oncology reviews the design and results to date of the original 30 patients from this phase 2 trial. This publication provides a more comprehensive summary than previously disclosed of patient characteristics, treatment regimen and more mature outcome data, including updated Kaplan-Meier curves estimating overall survival and PSA progression-free survival (PFS) as well as a swimmer’s plot of the 30 patients.

This study evaluated a heavily pre-treated patient population, 87% of which had received > 1 line of prior chemotherapy (80% docetaxel and 47% cabazitaxel) and 83% received prior abiraterone acetate and/or enzalutamide.

Observations in this study include a PSA reduction of at least 50% from baseline (PSA50) in 57% of patients, a PSA reduction of at least 80% from baseline (PSA80) in 43% of patients and a PSA reduction of > 96% in 20% of patients who were identified as ‘exceptional responders’. Regarding disease progression and survival, a median PSA PFS of 7.6 months and a median overall survival (OS) of 13.5 months were observed. Both the median PSA PFS and the median OS reflect improved outcomes versus the 6.3 months and 12.7 months for each endpoint, respectively, previously presented at the 2017 ESMO (Free ESMO Whitepaper) Congress.

Notably, patients with a PSA50 response had median PSA PFS of 9.9 months and median OS of 17.0 months compared to PSA PFS of 4.1 months and median OS of 9.9 months for those who did not achieve a PSA50 response. Additionally, clinically meaningful improvements in quality of life measures were observed.

17 patients (57%) had prostate cancer working group 2 (PCWG2) RECIST 1.1 evaluable nodal or visceral target lesions following CT scan at baseline. Confirmed objective responses were seen in 14 (82%) of these 17 patients, including complete and partial response rates of 29% and 53%, respectively. This response rate is greater than the 71% PCWG2 RECIST 1.1 objective response rate previously reported.

177Lu-PSMA-617 was well tolerated, with no significant dose-limiting toxicities observed. The most common treatment-related toxicity was Grade 1 xerostomia (dry mouth) seen in 87% of patients, which is higher than previously reported (63%), but generally didn’t require any intervention. The occurrence of treatment-related Grade 3-4 hematologic toxicity was low and comparable to the largest retrospective published cohort.1

The paper is available online at the following link: https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(18)30198-0/supplemental

Website Information

Endocyte routinely posts important information for investors on its website, www.endocyte.com, in the "Investors & News" section. Endocyte uses this website as a means of disclosing material information in compliance with its disclosure obligations under Regulation FD. Accordingly, investors should monitor the "Investors & News" section of Endocyte’s website, in addition to following its press releases, SEC filings, public conference calls, presentations and webcasts. The information contained on, or that may be accessed through, Endocyte’s website is not incorporated by reference into, and is not a part of, this document.