NewsRx.com
December 8, 2005
A new study presented at the International Conference on Molecular Targets and Cancer Therapeutics in Philadelphia, Pennsylvania, shows that phenoxodiol significantly delays tumor progression in men suffering from late-stage hormone refractory prostate cancer.
The meeting is sponsored by the American Association of Cancer Researchers (AACR), the National Cancer Institute (NCI), and the European Organization for Research and Treatment of Cancer (EORTC).
The antitumor effect in this phase Ib/IIa trial was dose-dependent. The trial was designed to end after 24 weeks of treatment, but had to be extended to the current 90 weeks because of the unexpected extended survival in some patients. Patients have been able to remain on phenoxodiol for this extended time without any evidence of toxicity.
Researchers administered various doses (20, 80, 200 and 400 mg) of phenoxodiol to men with metastatic, hormone-refractory prostate cancer to establish what level of anticancer effect the oral dosage form of this drug would provide and whether there was a dose-dependent effect. The phenoxodiol was administered in monthly treatment cycles comprised of 3 doses daily for 21 consecutive days followed by 7 days without treatment.
The original plan was to treat patients for a maximum of 6 treatment cycles. Except for antiandrogen therapy being continued in those who were receiving it pretrial, phenoxodiol was the only treatment. The age of the 26 subjects studied ranged from 55 to 85, the Gleason score was mean 8.04 (range 6-9), and the mean baseline PSA level was 56.3 pg/ml.
Response to therapy in these patients was determined on the basis of PSA response (a decline in PSA level compared to baseline of at least 50%), PSA doubling time (time for the baseline PSA level to double), and time to progression (length of time that patients remained on phenoxodiol based on PSA levels and clinical assessment).
Combining the data from the 2 lowest dosages (12 patients) and the 2 highest dosages (14 patients), the number of patients still on therapy after 6 months increased from 1 out of 12 (8.5%) to 10 out of 14 (71.4%), and the mean time to progression (length of time patients were deemed to be deriving a benefit from therapy) increased from 15 weeks to 47 weeks. This latter figure does not take into account 4 patients who remain on therapy after 42, 74, 82 and 90 weeks.
In terms of PSA levels, there were no PSA responses in the two lowest dosage groups, but 3 of the 14 in the two highest dosage groups experienced a PSA level reduction of 50% or greater from baseline. The PSA doubling time increased from a mean 18 weeks to 43 weeks, not including the 3 of 14 patients who remain on phenoxodiol therapy and whose PSA levels have yet to double. While it was not possible to measure tumor size in this study, an increase in PSA doubling time is generally regarded as reflecting a tumor response.
Phenoxodiol is being developed as a therapy for late-stage, chemoresistant prostate, ovarian and renal cancers.
Marshall Edwards, Inc., (MSHL) has licensed rights to bring phenoxodiol to market globally from its parent company, Novogen Limited (NVGN). This article was prepared by Biotech Business Week editors from staff and other reports. Copyright 2005, Biotech Business Week via NewsRx.com.
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