GTx-758 to be tested at lower doses in men with mCRPC


According to a media release issued yesterday by GTx, Inc., the U.S. Food & Drug Administration is allowing the company to proceed with a proposed, open-label, Phase II clinical trial of Capesaris® — also known as GTX-758 — in the treatment of men with metastatic, castration-resistant prostate cancer (mCRPC).

GTX-758 had previously been in development as an oral, first-line form of hormonal therapy for the treatment of men with advanced prostate cancer. However, safety issues indicated that the risk associated with the use of widespread and potentially long-term use of this drug were problematic (see prior commentary).

The new Phase II trial will be open to enrollment starting some time between July and September this year. The goal is to enroll 75 patients with mCRPC and to conduct an initial test of the activity and safety of GTX-758 at three different dose levels in these men (at 125, 250, and 500 mg daily). Patients must have evident metastatic disease and a rising PSA after first-line hormonal therapy. They will be maintained on their primary androgen deprivation therapy (ADT) while receiving GTX-758.

In addition to assessing the effects of GTX-758 in combination with first-line ADT on the PSA levels and disease progression of the target population, the company will also be monitoring effects on serum levels of free testosterone, effects on serum levels of adrenal androgen precursors, and the incidence and frequency of hot flashes and bone loss. A particular area of focus will be the incidence of venous thromboembolism and related events in patients in this trial, since this was the key adverse effect leading to stoppage of the earlier trial in men with earlier-stage disease (when GTX-758 was dosed orally at 750 mg/day).

Details of the new trial will presumably be forthcoming later in the year on the ClinicalTrials.gov web site (if you click here)

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