Stand by for a battle-royal over Alzheimer's disease (AD)-to take place in the British High Courts of Justice, no less. Shortly, in a unique court case, NICE (National Institute for Clinical Excellence), the UK's National Health Service drugs watchdog, will be challenged to defend its decision not to fund Alzheimer's drugs intended for use in the early stages of the disease.
Ranged on the prosecution benches will be two big guns of the pharma-ceutical industry, Pfizer and its marketing arm Eisai, aided and abetted by the Alzheimer's Society, a vociferous patient support group that equally loudly proclaims itself to have no ties with any drug manufacturers.
What's all the fuss about? Are the Alzheimer's drugs any good at all, and are there any alternatives? And what causes the disease in the first place?
Dementia and Alzheimer's
From near-obscurity only a generation ago, Alzheimer's disease is now probably, after cancer, the most feared disease of old age. Alzheimer's has been chillingly described as an affliction whose victims suffer the loss of qualities that define human existence.
Once considered a rare disorder, it is now known to be the most common type of senile dementia, defined as physical damage to the brain in old age that results in major changes to reasoning, memory, personality and behaviour. Until recently, the only way to distinguish Alzheimer's from other types of dementia was by post-mortem examination of the brain. A typical AD brain is found to be partly atrophied, with the brain cells clumped together in what are called 'neurofibrillary tangles' or 'plaques'.
The second major type of dementia is vascular dementia, where the interruption of the brain's blood supply, usually due to 'mini-strokes', causes brain cells to die.
These two main types of dementia can now sometimes be distinguished from each other by brain scans using either magnetic resonance imaging (MRI) or positron-emission tomog-raphy (PET).
Senile dementia is not as inevitable as many people might imagine: between 25 and 50 per cent of individuals over 85 are spared it. Nevertheless, dementia is on the increase, so the drug companies claim, because of the simple fact that we're
all living longer. It is believed to be incurable.
Big Pharma's offerings
Any prolonged chronic illness that is only ended by death is, of course, meat and drink to the pharmaceutical industry. And yet, perhaps surprisingly, there are relatively few drug treat-ments available for Alzheimer's. First on the market was tacrine (marketed as Cognex) in 1993. Like virtually all of its successors, tacrine is a so-called cholinesterase inhibitor, which acts by artificially maintaining levels of acetyl-choline in the brain. This important brain chemical is known to be reduced by as much as 90 per cent in AD sufferers; it's also believed to be important for memory, so finding a drug that can preserve the chemical in the brain makes sense.
In fact, the theory is fine-the trouble is the side-effects. After just a decade on the market, tacrine began to be no longer actively marketed after reports of severe liver toxicity. As much as 60 per cent of patients found the drug's side-effects to be intolerable at high doses. The final nail in tacrine's coffin was that, after all this, it really doesn't work (JAMA, 1998; 280: 1777-82).
Since then, three other drugs have come onto the market, all of which attempt to do the same trick of increasing acetylcholine in the brain. As expected, these drugs are all deadly rivals. Pfizer's Aricept (donepezil), has an advertising tagline that says 'when Alzheimer's hits home, Aricept can help'; Novartis' Exelon (rivastigmine) claims to be 'another step forward against Alzheimer's disease'; and Shire Pharmaceuticals/Janssen's Reminyl (galantamine) sells itself with the somewhat vague tagline 'Reminyl is now'.
So far, Pfizer is the only manu-facturer to have threatened a lawsuit against the recent NICE ruling that none of these drugs is really worth taking in the early stages of AD. Will the drugmaker win their case? Our prediction is no-and, frankly, because the evidence is stacked against them.
The only large-scale, truly indepen-dent clinical trial of Pfizer's Aricept was carried out by a team of British researchers at the University of Birmingham. In a double-blind trial that lasted for more than two years, Aricept was tested head-to-head against a placebo in over 500 patients who had mild-to-moderate AD.
The study's conclusions? Aricept works, but its benefits are very small-"below minimally relevant thresholds" (Lancet, 2004; 363: 2105-15). As study director Professor Richard Grey stated in the report: "Patients and their families would probably notice no difference if the drug was stopped."
What's more, even clinical trials funded by the drug companies them-selves failed to show much benefit with any of their products. For example, Oxford University researchers recently scrutinized data from 24 separate Pfizer-sponsored Aricept trials, involving more than 5000 patients at different stages of AD, and concluded that "the treatment effects are small and are not always apparent in practice". Add to that the strong likelihood of "many adverse events" such as nausea, vomiting, diarrhoea, muscle cramps, dizziness, fatigue and anorexia, and it's little wonder that there's what the researchers politely refer to as a "debate" over whether Aricept is worth a candle (Cochrane Database Syst Rev, 2006; 1: CD001190).
The same Oxford scientists have also examined another of Pfizer's claims-which is also supported by the strictly independent Alzheimer's Society-that Aricept helps prevent the onset of AD, stopping what is classified as 'mild cognitive impairment' (MCI) from turning into full-blown Alz-heimer's. The researchers' conclusion? According to their report: "There is no evidence to support the use of Aricept for patients with MCI. The putative benefits are minor, short-lived and associated with significant side effects" (Cochrane Database Syst Rev, 2006; 3: CD006104).
What of Aricept's two other rivals, however? Again, independent studies of the clinical data have exposed the drug companies' marketing hype.
With MCI, for example, Polish researchers concluded earlier this year that the efficacy of all three cholinesterase-blocking drugs was "questionable", especially given the high incidence of side-effects, some of which-as in the case of Reminyl-apparently can be fatal (Neurol Neurochir Pol, 2007; 41: 13-21).
As for full-blown AD itself, three groups of independent researchers all agree that the three drugs, although having slightly different modes of action, all produce broadly similar effects-or rather, a lack of effects. Their benefit to Alzheimer patients is variously described as "not large" (Cochrane Database Syst Rev, 2006; 1: CD005593), "limited" (Tijdschr Psychiatr, 2006; 48: 17-26) and "small" (Drugs Aging, 2007; 24: 155-67).
Nevertheless, Aricept remains the market leader in a highly profitable $3 billion a year business that is fore-casted to grow exponentially.
But there's one new drug that is beginning to challenge Aricept. It's called memantine (marketed as Ebixa, Axura, Namenda and Akatinol). Strictly speaking, it's not a drug, as it's derived from the naturally occurring mineral adamantine, and it also works in a different way from its pharmaceutical rivals. Developed by Merz, a German manufacturer of natural health products, the compound appears to protect brain cells against glutamate, the amino acid that is thought to be toxic to the brain in excess amounts and to trigger Alzheimer's.
Clinical trials of memantine have been promising, showing it to be particularly effective in moderate-to-severe AD, although it generally only slows mental decline rather than reverses it (Drugs, 2006; 66: 1515-34). Detailed testing has found that it appears to benefit attention and information-processing speed more than memory (Int J Geriatr Psychiatry, 2006; Nov 20; epub ahead of print).
Its side-effects are hardly greater than a placebo tablet, with a slight tendency to produce tiredness and dizziness. It is widely used in Germany, often in preference to the standard drugs; however, in Britain, it is still considered experimental.
Meanwhile, gradually emerging into the limelight are a number of promising plant-based treatments, some of which turn out to have properties that seem almost tailor-made for AD.
Take the humble culinary sage plant, Salvia officinalis. In addition to having potent antioxidant and anti-inflammatory effects, sage is known to have anticholinergic effects similar to Aricept's. When tested against placebo in a recent clinical trial, 60 drops of sage oil a day was often found to be better than Aricept at maintaining mental functioning in people with mild-to-moderate AD-and without any side-effects (J Clin Pharm Ther, 2003; 28: 53-9). Sage oil can also improve memory in younger people, too.
Lemon balm (Melissa officinalis) has been found to bind to the brain receptors believed to be involved with anxiety, thus reducing the agitation symptoms seen with AD. Particular strains of the plant have also proved able to slow the decline of mental functioning (Curr Pharm Des, 2006; 12: 4613-23). However, although some proponents recommend these plants as aromatherapy for Alzheimer sufferers, the evidence is considered "inconclu-sive" (Aust NZ J Psychiatry, 1999; 33: 789-99).
The classic herbal memory-enhancer is Ginkgo biloba, which has been proven in numerous clinical trials to benefit mental faculties in people of all ages. Germany is where it's most used for Alzheimer's, as even German conventional doctors consider it prefer-able to the pharmaceutical drugs on offer.
Although it's by no means a miracle-worker, Ginkgo has been shown to benefit virtually all AD patients to some degree, and about a third of them quite significantly. The recommended dosage is 240 mg/day of the Ginkgo extract codenamed 'EGb 761'; the benefits normally show up within six months (Pharmacopsychiatry, 2003; 36: 297-303). It's even been suggested that Ginkgo might help prevent the onset of AD but, so far, no research has been done to test its possible role in Alzheimer's prevention.
What of the other 'smart drugs' that are sometimes claimed to be memory-enhancers for the able-bodied? Of these, only nicergoline (derived from ergot) appears to have any evidence of benefit, with up to a threefold improvement on some performance measures in AD (Cochrane Database Syst Rev, 2001; 4: CD003159). Vinpocetine and piracetam, although better known, don't appear to have been adequately tested in Alzheimer's patients to come to any firm conclusions.
On the near horizon, the curry spice curcumin is being investigated as a potential anti-AD compound, after it was recognized that people in India have lower rates of the disease. Lab tests by neurologists at UCLA have already shown that curcumin can repair brain cells damaged by AD, and clinical trials are currently underway (J Alzheimers Dis, 2006; 10: 1-7).
Traditional Chinese medicine offers two sets of herbal mixtures: Yi-Gan San is a combination of seven different plants, headed by angelica root; and Ba Wei Di Huang Wan (BDW) com-prises eight herbs, including cinnamon and peony. Initial research shows that they may be useful in AD (Evidence-Based Complement Altern Med, 2006; 3: 441-5).
There is currently excitement over one Chinese herb in particular, a rare club moss called Huperzia serrata.
Five years ago, an extract of the moss-huperzine alpha (Hup-A)-was tested in more than 200 Chinese diagnosed with mild-to-moderate AD. The results were described as "remarkable". After taking 400 mcg of Hup-A for less than three months, 60 per cent of the patients were observed to be "clinically on the mend". Only about a quarter of patients failed to respond. Side-effects were "mild and transient" and, in any case, affected very few of the patients (Zhonghua Yi Xue Za Zhi, 2002; 82: 941-4).
How does Hup-A work? It's thought to increase acetylcholine levels in the brain. But, in fact, it's much better than that. It penetrates the brain more effectively than the current drugs, and lasts longer. It also has a wider range
of effects, including protecting cells against further damage from inflammation and oxidation (Acta Pharmacol
Sin, 2006; 27: 1-26). Here again, a clinical trial is currently ongoing.
The Chinese also use acupuncture for Alzheimer's, and there is evidence that it may work (Zhongguo Zhen Jiu,
2005; 25: 390-2). In a Westernized varia-tion of this, doctors have tested TENS (transcutaneous electrical nerve stim-ulation) therapy. Applied to various parts of the body (even the face), TENS has been shown to have some value, particularly in the early stages of AD. However, according to the Japanese doctors using it, the therapy needs to be repeated to sustain benefits beyond six months (Front Med Biol Eng, 2002; 11: 237-47).
One possible AD treatment is chelation therapy. Often derided as mere quack-ery, chelation has been used for decades by frontier-spirited cardiol-ogists to combat heart disease. The treatment involves transfusing a chemical cocktail into the bloodstream that will bind itself to harmful agents and carry them away. Chelation's earliest use was to remove toxic levels of lead from workers in the battery and paint industries, but it's now finding a revival in Alzheimer's patients.
The argument is this: if metal toxicity is involved in AD, then chelation may be able to bind and flush away the harmful metals before they can cause brain damage.
One of the first trials of chelation used clioquinol as the chelating agent. The results were promising, showing a slight clinical improvement after three weeks (Dement Geriatr Cogn Disord, 2001; 12: 408-14). However, the results of
the only subsequent trial were less encouraging (Cochrane Database Syst Rev, 2006; 1: CD005380).
Despite these disappointing find-ings, a whole slew of researchers across the globe-from Osaka University to Harvard-are actively pursuing the chelation route in hopes of making a breakthrough. Some scientists are even suggesting using 'nanoparticles' to trick the brain into allowing more powerful chelating agents past its barriers (Neurosci Lett, 2006; 406: 189-93).
The fact that researchers are being forced to consider such high-tech solutions says two things: the existing treatments aren't working; and Alzheimer's may be a rather tougher nut to crack than we thought.