Novogen's phenoxodiol shows promise in cancer trials

Novogen (ASX: NRT) has announced updated results from two clinical trials of its anti-cancer drug phenoxodiol, which is being developed by the company's US-based subsidiary Marshall Edwards (LSE AIM: MSH; Nasdaq: MSHL).

The results were presented at this week's American Association of Cancer Research conference in Florida.

Novogen managing director Christopher Naughton said the results from both studies were very encouraging.

"It's all very positive really," he said.

In the first study conducted at Perth's Sir Charles Gairdner and St John of God Hospitals and Monash Medical Centre in Melbourne, a Phase Ib/IIa trial examining the biological activity of oral phenoxodiol in 24 late stage prostate cancer patients with rising prostate specific antigen (PSA) levels, a dose related response was observed. Out of the twelve patients receiving the two highest doses, two patients showed evidence of stabilisation of serum PSA levels after receiving the drug three times daily for three weeks, while six patients showed a decrease -- in two cases the decrease was more than 75 per cent. No toxicity was reported in the study.

Lead investigator on the study Dr Robert Davies, from Sir Charles Gairdner Hospital, said that late stage prostate cancer was notoriously unresponsive to chemotherapy.

While the trial has been completed, final analysis of the results have not been released by the investigators, Naughton said, But the company and the investigators are already considering a larger follow up trial to investigate phenoxodiol as a monotherapy as well as in combination with other chemotherapeutics.

The second set of trial results reported at the AACR meeting were from the ovarian cancer study conducted by Yale University researchers. The Phase II trial looked at phenoxodiol as a monotherapy in 40 late stage unresponsive, recurrent ovarian cancer patients, and included a follow up component where patients returned to previous treatment regimes after the phenoxodiol study was completed to assess its chemo-sensitiser properties.

Results presented at the meeting indicate that although levels of ovarian cancer marker CA125 had stabilised or dropped in 25 per cent of patients after six weeks of treatment, after three months, only four of these patients showed stabilisation based on CA125 levels. Almost all of the responder patients came from the lower doses tested, confirming preclinical laboratory studies that showed that phenoxodiol had a greater effect on ovarian cancer cells at lower doses.

No data was provided on other endpoints of the study including shrinkage of the tumour mass or improved clinical status, but again, toxicity was not a problem.

But the company said that more relevant data came from the follow-up part of the study where patients were put back on their previous treatment regime. In a group of ten patients who received paclitaxel, eight showed an immediate decline in the CA125 levels. Five of the ten had been previously considered to be resistant or unresponsive to paclitaxel, and four out of those five showed the improved response after phenoxodiol treatment, with three remaining alive after an average of 292 days.

Yale University investigator Dr Thomas Rutherford said it was very exciting that preliminary findings suggested that phenoxodiol could act as a chemo-sensitiser, restoring the cancer's susceptibility to chemotherapeutics like paclitaxel.

The next step, according to Naughton, will be a combination study to look at the effect of combining treatment with phenoxodiol and other chemotherapeutics. He said the trial would be likely to start before the end of the first half of 2004.

Two laboratory studies were also presented at the AACR. Yale researchers examined the chemo-sensitising properties of phenoxodiol in ovarian cancer cells showing that the drug restores sensitivity to taxane drugs including docetaxol, as well as to platinum drugs such as carboplatin. And an NIH study demonstrated the ability of the drug to kill head and neck cancer cells, including some that were highly resistant to standard anti-cancer drugs.

At the time of writing, Novogen's share price had risen more than eight per cent to AUD$6.46.