TO COKE fiends, it must sound too good to be true鈥攂eing paid to snort
cocaine. And sure enough, there鈥檚 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 鈥渉igh鈥� in the brain
(see New 杏吧原创,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. 鈥淧atients are not going into this study
to quit,鈥� admits John St Clair Roberts, the company鈥檚 medical director. 鈥淭hey鈥檙e
generally going in to be paid.鈥� But he points out that if they weren鈥檛 in the
trial they would still be taking the drug.
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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. 鈥淏ut we don鈥檛 know how
much antibody you need for the vaccine to be effective,鈥� 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 鈥渉igh鈥�, says Roberts. 鈥淚t鈥檚 all we have to go on at this stage, but
it鈥檚 quite encouraging.鈥�
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 鈥渟norted鈥�.
Roberts says that addicts would only be given the vaccine during the period
it takes to quit. 鈥淢ost psychiatrists say that after 9 or 10 months, former
addicts don鈥檛 relapse,鈥� says Roberts. 鈥淚n the real world, if you鈥檙e through
that, you鈥檙e pretty safe.鈥� 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 Shaham
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鈥檚 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鈥檇 received while on the drug, such as
lights and sounds. Roberts says Shaham鈥檚 study merits attention.