A phase I trial of AEZS-108 in castration- and taxane-resistant prostate cancer.

Abstract

e15153 Background: The prognosis for patients with castration-resistant prostate cancer (CRPC) remains suboptimal and targeted therapies should be explored. One potential target is the receptor for luteinizing hormone-releasing hormone (LHRH), which is highly expressed on prostate cancer cells. AEZS-108 is an LHRH-cytotoxic hybrid whose rational design covalently couples an LHRH agonist and the cytotoxic doxorubicin. AEZS-108 exploits the presence of LHRH receptors to target delivery of the cytotoxic. We report the phase I trial of AEZS-108 in men with taxane-resistant CRPC. We also report correlative studies of a novel circulating tumor cell (CTC) capture device that will provide enumeration of CTCs and results from AEZS-108 internalization studies that exploit the auto-fluorescence of doxorubicin in captured CTCs. Methods: This is a single-arm, dose-escalation phase I study in men with CRPC to confirm the dose established in a completed phase I trial in females. Eligibility criteria included adequate organ function and progression of disease despite prior therapy with an LHRH agonist and at least one taxane-based regimen. Patients were required to discontinue LHRH agonists to avoid receptor competition. Due to potential cardiotoxicity, patients with an ejection fraction < 50% or prior exposure to doxorubicin or mitoxantrone were excluded. Pituitary function was closely monitored. Patients received AEZS-108 every 21 days for up to 6 cycles until progression or unacceptable toxicity. The primary endpoint was safety. Results: Enrollment began in November 2010 and is ongoing. Currently, 13 patients have been enrolled. The first two planned dose levels had no dose-limiting toxicities observed. Two patients on the third dose level experienced a dose limiting toxicity. The second dose level has been reopened for expansion. There have been no cardiac or pituitary toxicities. At the time of submission, a decrease in PSA was noted in 6 of the 13 patients. Final results detailing safety, response and the suggested dose for the phase II portion will be reported. All correlative studies will also be reported. Conclusions: In general, AEZS-108 has been well tolerated. The phase II portion of the study will begin once the MTD is established.