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.