Biotech profile: Novogen

Research into the potential of the plant polyphenols known as flavonoids has been ongoing for decades, particularly for the beneficial biochemical and antioxidant effects the compounds seem to confer.

One particular group within the flavonoid class, the phytoestrogen compounds known as isoflavones, are of particular interest as both nutritional supplements and in therapeutic applications.

Primarily derived from the legume family, there are several main isoflavones of interest to basic researchers and the pharmaceutical world, particularly genistein and daidzein, found in high concentrations in red clover and soya beans.

Not only do isoflavones have oestrogenic activity, and are therefore being used as a dietary supplement for menopausal women, but they seem to have quite pronounced anti-cancer and pro-cardiovascular effects.

Sydney company Novogen has taken a very close look at these compounds and has now developed a technology platform to produce synthetic molecules with highly predictive effects.

Using a quantitative structure activity relationship (QSAR) database, Novogen’s scientists are able to create new molecules by making subtle changes to the structure of their compounds, which result in subtle changes in activity.

When Novogen was set up in 1992, the idea was to use isoflavones in dietary supplements as a first step, with the main game being to manufacture them into therapeutic applications, the company’s director of research, Professor Alan Husband says.

That first step is a going concern: Novogen’s consumer business produces a number of dietary supplements, the lead product being Promensil, an adjunctive treatment for menopause. The consumer business is becoming self-sustaining while the rest of the company gets on with developing new therapeutic applications.

“These isoflavones have oestrogenic activity and therefore can help replace the missing oestrogen in menopause, but that’s only a very small part of what we are now doing,” Husband says.

“We discovered that the naturally occurring isoflavones also have very pronounced anti-cancer activity. If you add these isoflavones to cultures of cancer cells, we found the cancer cells were dying.”

“There is also improved cardiovascular health, and indication of anti-inflammatory activity, so the original proposition was that even though these dietary supplements might be useful, the real opportunity for us was to manufacture totally new flavonoid-type molecules that we’d deduced originally – and now we can actually predict – will have activities in cardiovascular, anti-inflammatory and anti-cancer areas.”

One of the first compounds with anti-cancer potential that Novogen developed was phenoxodiol, which seems to have quite remarkable properties. It works against a broad range of cancers in vitro – in fact, almost every cancer cell line the company tested it against was susceptible – but it has no effect on healthy cells, Husband says.

“We now understand in exquisite detail how that works: it targets the abnormal signal transduction which occurs in cancer cells. The whole hallmark of a cancer cell is that pro-survival mechanisms are upregulated and cell death mechanisms are switched off.

“We found that phenoxodiol and its downstream relatives like triphendiol and some others in the pipeline bind to a surface oxidase that is expressed in a different form on abnormally dividing cells.

“And it’s sufficiently different, both structurally and functionally, to enable us to target that specifically on cancer cells, but it’s not so strongly expressed on healthy cells.

“So this has given us a molecule that is not only very effective in producing an anti-cancer benefit, but it’s proven to be almost entirely safe in clinical use.

“It’s absolutely remarkable, because I think it’s the first time that there has been a relatively safe but apparently effective anti-cancer agent.”

---PB--- Ovature cut short

After realising the potential of isoflavones in cancer applications, particularly phenoxodiol and its more recent cousin triphendiol, Novogen decided to set up a new company based in the US to focus purely on oncology.

That company, Marshall Edwards, Inc., is still majority owned by Novogen, and has taken phenoxodiol into Phase III trials in late-stage, chemoresistant ovarian cancer, the OVArian TUmor REsponse or OVATURE trial, which has recently been cut short to save money during the economic downturn.

The main objective of this trial was to demonstrate that phenoxodiol improves sensitivity to platinum in platinum-resistant patients. Marshall Edwards received a Special Protocol Assessment from the US FDA for the trial, which is taking place in 75 hospitals around the world.

The trial was expected to require 340 patients, although the FDA had agreed that once 95 patients fully completed the trial and were documented, Marshall Edwards would be able to undertake a preliminary analysis.

New patient recruitment has now ceased and the interim analysis will be done on the data collected from 141 completed and current patients.

Marshall Edwards is also running a Phase II study in prostate cancer, the second arm of its prostate cancer strategy.

The first Phase II study showed substantial improvement in progression-free survival in hormone-refractory prostate cancer with phenoxodiol as a monotherapy, Husband says, and the second study is comparing hormone-refractory patients with another group who have early-stage disease.

“After the first diagnosis patients usually have prostatectomy or brachytherapy and that ablates the tumour inside the prostate gland. You then wait to see if anything happens and if the disease does recur it is usually heralded by an increase in prostate-specific antigen (PSA), so there is a big group of patients who have got rising PSA but they haven’t yet got any detectable tumour.

“You can’t treat them for the tumour if you can’t find it. They know they are on their way towards disease progression and normally they treat those patients with hormone ablation, so what we are proposing here is that phenoxodiol may have a benefit in that early stage, watchful waiting period, having demonstrated benefit in late-stage disease.

“There also may be an even stronger benefit in early stage disease. And once we know the answer to that we can progress into Phase III with either early or late-stage, or both.”

Husband reiterates that throughout all of these studies, there is no safety issue with phenoxodiol. More than 400 patients have been treated in a variety of studies to date, and there have been no serious adverse events attributable to the drug, he says.

---PB--- How it works

The surface oxidase that phenoxodiol targets is NADH-oxidase, which is part of a redox pump found in all healthy cells.

In cancerous cells, that oxidase is both structurally and functionally different from the form found in healthy cells, as it maintains a much higher rate of proton transport, which seems to enable the cells to have the survival capacity characteristic of cancer.

The cell’s pro-survival protein pathways – especially the Akt pathway – are maintained under the influence of this activated oxidase. The pro-survival FLIP protein also seems to be activated, Husband says.

“When phenoxodiol and our other drugs bind to the oxidase, it blocks those pathways,” he says. “It’s like putting a cork in an exhaust pipe, with those downstream pro-survival pathways blocked.

“With the Akt pathway switched off, caspase is produced, which is the executioner enzyme. At the same time, and this is the nice kicker, under the influence of the Akt pathway there is another that leads to expression of the FLIP protein. FLIP is an agent which inhibits the death receptor, so a cancer cell becomes unresponsive to death signalling.

“We’ve shown that phenoxodiol and our other compounds down-regulated not only Akt but also FLIP, which restores the death receptor, the Fas ligand.

“The importance of that is not just that we enable the cells to receive environmental signalling, but drugs like platinum and taxane deliver their effect through the Fas ligand.

“So in addition to being able to use these drugs as single agent monotherapies, they also reactivate the Fas ligand receptor system, which makes the cells more sensitive to platinums and taxanes.”

A relative of phenoxodiol, triphendiol, is now being developed as a combination therapy with gemcitabine (marketed as Gemzar by Eli Lilly) for treatment of pancreatic and bile duct cancer. Marshall Edwards received an IND from the FDA at the end of last year, allowing it to move into human clinical trials in the US.

Some human trials have already been carried out in Australia, with the same safety profile as phenoxodiol. Triphendiol seems to work in exactly the same way as phenoxodiol, only better in pancreatic cancer targets than the latter.

It also seems to be able to act in both a caspase-dependent and caspase-independent manner, which Husband describes as a very interesting development.

---PB--- Cancer stem cells

While Marshall Edwards concentrates on the oncology program, Novogen continues to develop new compounds that the subsidiary has first right of refusal to licence.

One of these is a new compound called NV-128, which works by targeting the mTOR cell survival pathway and kills cancer in an entirely caspase-independent manner.

As Husband points out, mTOR is the real buzzword in oncology at the moment, for two reasons. One is that it is highly expressed in cancer cells and is a mechanism by which cancer cells can be killed without switching on caspase.

The second reason is that mTOR is the survival mechanism most important in cancer stem cells.

“What we’ve been doing in treating cancer to date is missing the point,” he says. “We’ve been treating the tumour without treating the underlying cause of the tumour, which is these cancer stem cells.

“They are out there, unidentifiable, they are not proliferating, they don’t get killed by anti-proliferative drugs, and so the cutting edge work is that cancer stem cells need to be addressed if you are really going to cure cancer.”

Big Pharma has taken a keen interest in mTOR, with much attention being paid to developing rapamycin analogues which effectively inhibit one of the mTOR pathways, mTORC1.

In an unfortunate twist, however, blocking this pathway promotes the up-regulation of an escape pathway involving formation of mTORC2.

“The real challenge now is to produce mTOR inhibitors that block both C1 and C2, and NV-128 does exactly that,” Husband says.

“We feel we are in a fantastic position here to develop a whole new generation of anti-cancer agents that target cancer stem cells, which also have a significant impact on established tumours, which are safe and which don’t allow resistance to develop.”

NV-128 seems to have activity against a broad range of tumours in vitro, but Novogen is concentrating on ovarian and non-small cell lung cancer. “For strategic reasons, non-small cell lung cancer is the target we’d like to pursue, but it is also highly active against ovarian cancer,” Husband says.

“The board of Marshall Edwards is considering its position with regard to licensing it in, and in the meantime we are undertaking all of the toxicology screens necessary to get approval for human use.”

---PB--- Anti-inflammatory and cardio on hold

Apart from the oncology work, Novogen has recently been using its flavonoid scaffold to develop a series of compounds that are promising in both anti-inflammatory and cardiovascular diseases.

Again, the company has had to put the development of these compounds on hold while the economic climate is so poor, but hopes to pick them up again when market conditions become more favourable.

In addition to Marshall Edwards, Novogen some years ago established a subsidiary company in the US called Glycotex. This is the result of some intellectual property Novogen had in its portfolio around carbohydrate chemistry which a group of investors were keen on pursuing.

This company has produced a compound called Glyc101 that is aimed at stimulating cellular activity in wounds to promote healing. It promotes both macrophage activity to clean the wound as well as epithelialisation.

This company has its own CEO and direction. Novogen itself prefers to remain as a drug discovery and development company and to let others deal with regulatory approvals, manufacturing and retailing, Husband says.

“We don’t propose to be a fully fledged pharma company,” he says. “Our business model is to develop drugs to clinical proof of concept. In the case of phenoxodiol we’ve gone beyond that into Phase III but once we have clinical evidence of safety and efficacy, the plan is to out-license to a major pharma or a big biotech.

“It’s not the only way but I think it’s the best way for a company that has a big pipeline on the cards. If we only had one drug we might hang on to it, but we’ve got so many drugs and the opportunity is endless.”

The consumer business brings in some revenue, although the research and development side still depends on investors. Like everyone else, Novogen is at the mercy of economic conditions, but it has cash in hand to ride out the storm, he says.

“We’ve been considering what economies we can put in place, but we are certainly not in as bad a position as many biotechs. A high percentage of biotechs globally have less than six months cash, and there is either going to be a lot of consolidation or a lot of companies going into liquidation. We are not in that position and we expect to be able to weather the storm.”

---PB--- Biosketch

Professor Alan Husband had a distinguished research career in immunology before joining Novogen. He maintains a position as a professor of veterinary pathology at the University of Sydney, where he still does some teaching and research.

He worked as a consultant to Novogen for some years before joining full-time as director of research in 1996. “I became captured by the science,” he says. “It was really interesting science and the opportunity to get into commercialisation is what really attracted me.”

Novogen’s research team comprises a dedicated chemistry team producing its molecules and working on the QSAR database, a biological discovery team screening for various indications, and an extensive network of collaborators throughout the world.

One of these collaborators is Yale University Medical School’s gynaecological oncology group, which has worked with Novogen for many years developing its drugs for ovarian and cervical cancer. “They are such an integral part of this team now that they even feel like phenoxodiol is one of their drugs,” he says.

There is a collaboration with the University of Alabama in Birmingham in pancreatic cancer, and two with other Yale University groups in prostate and in pancreatic cancer.

In the UK there is a collaboration with the Hammersmith Hospital and Imperial College London in ovarian cancer, and in New Zealand a collaboration with Professor Michael Berridge at the Malaghan Institute of Medical Research.

In Australia the company has worked with a number of expert groups such as Professor Michael James from the Royal Adelaide Hospital, Dr Robert Davies from Sir Charles Gairdner Hospital in Perth on prostate cancer, and Dr Paul Mainwaring at Brisbane’s Mater Hospital on ovarian cancer.