Pubdate: Sat, 14 Jul 2001
Source: New Scientist (UK)
Copyright: New Scientist, RBI Limited 2001
Contact:  http://www.newscientist.com/
Details: http://www.mapinc.org/media/294
Author: Andy Coghlan

NO MORE HIGHS

We'll Soon Know If A Vaccine Can Make You Immune To Charlie's Charms

TO COKE fiends, it must sound too good to be true-being paid to snort 
cocaine. And sure enough, there's a catch. The addicts in New York who will 
soon have this privilege must first take a pioneering vaccine intended to 
conquer drug addiction.

The vaccine, called TA-CD, triggers the production of antibodies against 
cocaine. The hope is that these antibodies will mop up the drug in the 
blood before it can trigger the usual "high" in the brain (see New 
Scientist, 10 June 2000, p 22).

This week, Xenova of Slough, Berkshire, was given the go-ahead by the US 
Food and Drug Administration for the New York trial, in which volunteers 
who have been vaccinated will be given cocaine. "Patients are not going 
into this study to quit," admits John St Clair Roberts, the company's 
medical director. "They're generally going in to be paid." But he points 
out that if they weren't in the trial they would still be taking the drug.

The immune system usually ignores cocaine. To make the body react against 
it, researchers have bolted cocaine molecules onto the cholera toxin. When 
the body sees cocaine as part of the combo, it produces antibodies against 
the drug.

Xenova, which acquired the vaccine when it merged with Cantab 
Pharmaceuticals of Cambridge, this week released results of a preliminary 
American trial on nine cocaine addicts. After receiving four shots of the 
vaccine, the addicts produced twice as many anti-cocaine antibodies on 
average as the 34 volunteers who had taken part in an earlier trial with 
only three shots. "But we don't know how much antibody you need for the 
vaccine to be effective," says Roberts.

Still, there are anecdotal signs that the vaccine works. When two of the 
nine volunteers relapsed and took cocaine, they reported there was some 
attenuation of their "high", says Roberts. "It's all we have to go on at 
this stage, but it's quite encouraging."

The Xenova scientists now need to find out if addicts can override the 
effects of the antibodies by taking more cocaine than usual. This would be 
dangerous, as the drug damages the heart. Also, they need to be sure it 
works against crack cocaine, which acts faster than other forms because it 
is purer and is inhaled rather than "snorted".

Roberts says that addicts would only be given the vaccine during the period 
it takes to quit. "Most psychiatrists say that after 9 or 10 months, former 
addicts don't relapse," says Roberts. "In the real world, if you're through 
that, you're pretty safe." They could receive boosters if they later 
encounter stresses that make them prone to relapse, he says.

But there are signs that the craving may get worse with time. Yavin Shaharn 
and his colleagues at the National Institute on Drug Abuse in Baltimore 
looked at craving by seeing how frequently rats pressed a lever that 
previously gave them cocaine. In this week's Nature (vol 412, p 141), the 
team reports that the lever-pressing progressively increased over 60 days 
whenever the rats were reminded of their habit with cues they'd received 
while on the drug, such as lights and sounds. Roberts says Shaham's study 
merits attention.
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MAP posted-by: Jay Bergstrom