New Cocaine Vaccine Is Safe but Has Limited Efficacy

No pharmacotherapy exists for cocaine dependence. Preclinical and open-label studies suggest that vaccination to produce anticocaine antibodies attenuates cocaine’s reinforcing effects. This randomized, double- blind, placebo-controlled clinical trial evaluated the safety and efficacy of a cocaine vaccine among 115 volunteers recruited from a US urban methadone maintenance program. Over the 12-week intervention period, 109 of 115 subjects received 5 injections of vaccine or placebo. Follow-up was at 24 weeks.

• The most common adverse effects were injection site induration and tenderness. There were no treatmentrelated serious adverse events, study withdrawals, or deaths.

• The frequency of cocaine-free urine samples during weeks 1–4 and weeks 5–24 did not differ between treatment conditions in intent-to-treat analyses.

• The 38% of vaccinated subjects who attained a high serum IgG (antibody) level (≥43 μg/mL) had more cocainefree urine samples (45%) than those with a low IgG level or those who received placebo (35%).

• The proportion of subjects having a 50% reduction in cocaine use was greater in subjects with a high IgG level (53%) than in those with a low IgG level (23%) during weeks 8–20, but there was no difference in complete abstinence.

Comments:

The vaccine in this study appears to have reduced but not eliminated cocaine use for 2 months in the minority of cocaine-dependent persons who had a high antibody response. Before this approach can be considered for routine clinical use, better vaccines that generate a sustained blocking antibody level in a larger percentage of individuals and with a less intensive vaccination schedule are needed.

Peter D. Friedmann, MD, MPH

Reference:

Martell BA, Orson FM, Poling J, et al. Cocaine vaccine for the treatment of cocaine dependence in methadonemaintained patients: a randomized, doubleblind, placebo-controlled efficacy trial. Arch Gen Psychiatry. 2009;66(10):1116–1123.