In April 2012 we had noted that Tokai Pharmaceuticals was planning to initiate a Phase II trial of its investigational drug galeterone (also known as TOK-001) in the treatment of men with castration-resistant prostate cancer (CRPC). The company has now announced that it has the funding to expand enrollment in this Phase II trial.
The first patient was enrolled in this Phase II trial (the so-called ARMOR2 trial) back in December 2012. However, the ARMOR2 trial is a two-part trial. We can effectively think of the ARMOR2 trial as being, initially, a Phase IIa trial, in which a relatively small number of patients are tested to determine a dose of galeterone that is both effective and as safe as possible in the treatment of men with CRPC and then a subsequent Part IIb trial in which a significantly larger number of patients are treated with the dose established as being optimal in Part IIa.
The precise dose levels of galeterone being tested in the Part IIa section of the trial are not specified in the information about the ARMOR2 trial available on the ClinicalTrials.gov web site, but we do know from earlier Phase I trials that, in men with CRPC, galeterone can induce significant elevations in enzyme levels in liver function tests, so the Part IIa section of the ARMOR2 trial has presumably been designed to find a dose level for galeterone that is effective in the treatment of CRPC but which minimizes the risk for elevations in liver enzyme function.
Patients who are interested in considering participation in the ARMOR2 trial must have castration-resistant disease and can either be treatment-naive (after progression on standard forms or androgen deprivation therapy [ADT]) or they can have progressed while receiving treatment with abiraterone acteate (Zytiga). Up to 196 patients may be enrolled in ARMOR2 in total. The primary endpoints of the study are reduction in PSA level and safety. This is not a randomized, placebo-controlled trial, so all patients will receive galeterone and apparently the patients who do respond to therapy will have the opportunity to continue treatment in an extension arm of the trial. Patients are currently being enrolled at four different sites around the USA, and at least two more are scheduled to start enrolling patients in the not too distant future. Quite how many centers may be enrolling patients in the Phase IIb section of the ARMOR2 trial is not yet clear.