NicVax, an anti-nicotine vaccine developed with NIDA support and owned by Nabi Pharmaceuticals, recently was evaluated in a large Phase III clinical trial. The vaccine did not perform as hoped with respect to the designated main clinical outcome: When assessed at 12 months, the percentages of vaccine-treated and control-group smokers who reported at least 16 weeks of continuous abstinence were roughly equal. It is important to understand these results in context.
Vaccines have a unique role to play in a comprehensive strategy to help people overcome addictions. A successful vaccine will make it easier for addicted individuals to establish and maintain abstinence. It will reduce the chances that isolated lapses into drug taking escalate into protracted relapses. Ideally, a single dose will remain effective for months or longer, eliminating the potential, seen with shorter-acting agents, for missed doses and consequent gaps in protection.
The development and evaluation of a vaccine occurs in many stages, from in vitro proof-of-concept studies to in vivo laboratory tests to small-scale and then large-scale clinical trials. At each stage, researchers hope that the results will meet criteria for proceeding to the next, and they gather information to enable them to make improvements if any are needed. Negative test or trial results may be the end of the road for a vaccine, but more often they are part of the stepwise accumulation of knowledge that precedes success in all medication development. The NicVax trial has provided the vaccine's developers with data rich with information that may direct them toward modifications of the vaccine itself or in the manner of its delivery, or other adjustments.
While NABI is continuing its research, NIDA is not presently funding further development of NicVax. However, we are supporting research on other vaccine strategies for nicotine, and for cocaine, heroin, and methamphetamine abuse. All these vaccines are designed to work in essentially the same way: They induce the immune system to generate antibodies that bind to the target drug, forming compound molecules that are too large to move from the bloodstream into the brain. Denied access to the brain, the drug cannot produce the reinforcement, or "high," that is a major component of the motivation to continue drug use. Individuals who use a drug without obtaining its reinforcing effects are expected sooner or later to shed the powerful mental associations between the drug and pleasure that underlie craving and relapse.
As a complex disease that affects diverse populations, addiction is unlikely to succumb to a single therapeutic approach. NIDA continues to view vaccines as a potentially powerful tool among an array of tools that will be necessary to relieve individuals, families, and communities of the burden of addiction
Sincerely,
Nora D. Volkow, M.D.
Director