Tokai Pharmaceuticals has reported additional data from a Phase 1 safety and proof-of-concept study investigating galeterone (TOK-001), in patients with castration-resistant prostate cancer (CRPC).
Galeterone is a proprietary small molecule, oral drug that disrupts the growth and survival of prostate cancer cells via a new triple mechanism of action.
The Phase 1 proof-of-concept clinical trial, part of the Androgen Receptor Modulation Optimized for Response (ARMOR) clinical development programme, enrolled 49 patients to assess escalating dose levels of galeterone.
The study also evaluated safety and reduction in prostate-specific antigen (PSA) levels from baseline levels. Patients who responded to therapy had the option to continue treatment with galeterone in an extension arm of the trial.
The efficacy tests demonstrated that 24 patients had PSA reductions of 30% or more, of which 11 had reductions of 50% or more.
Tokai Pharmaceuticals president and chief executive officer, Martin Williams, said that while other approved and experimental CRPC therapies act via a single target, galeterone is differentiated as the only prostate cancer drug in development that combines three distinct mechanisms of action in one compound for a unique multi-target approach.
"Galeterone acts in three ways against the key driver of CRPC, androgen receptor signalling: it blocks ligand synthesis, blocks ligand receptor binding and degrades the receptor itself," Williams added.
"The efficacy observed in the galeterone ARMOR1 study, with both biochemical and radiological responses, combined with a favourable safety profile, support our Phase 2 clinical trial programme to be initiated in the second half of 2012."
In preclinical studies, galeterone decreased androgen receptor levels in prostate tumours, while acting as a selective CYP17 lyase inhibitor and androgen receptor antagonist.
CRPC is an advanced, difficult-to-treat form of prostate cancer that occurs when the disease progresses despite the use of androgen deprivation therapy.
Image: Micrograph of prostate adenocarcinoma, acinar type, the most common type of prostate cancer. Photo courtesy of: Nephron.