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NicVAX is an experimental conjugate vaccine intended to reduce or eliminate physical dependence to nicotine. According to the U.S. National Institute of Drug Abuse, NicVAX can potentially be used to inoculate against nicotine addiction. This proprietary vaccine is being developed by Nabi Biopharmaceuticals of Rockville, MD. with the support from the U.S. National Institute on Drug Abuse. NicVAX consists of the hapten 3'-aminomethylnicotine which has been conjugated (attached) to ''Pseudomonas aeruginosa'' exoprotein A. Early trials of NicVax were promising, two successive phase III trials showed results no better than placebo,〔()〕〔()〕 and a more recent study showed that the drug decreased subjects' cravings for cigarettes. Although NicVAX failed its clinical trials, the quest for a Nicotine vaccine goes on at Selecta Biosciences. ==Mechanism== Nicotine is a small molecule that after inhalation into the lungs quickly passes into the bloodstream, subsequently crossing the blood–brain barrier. Once in the brain, it binds to specific nicotine receptors resulting in the release of neurotransmitters, such as dopamine and norepinephrine. NicVAX is a relapse prevention therapy designed to stimulate the immune system to produce antibodies that bind to nicotine in the bloodstream and prevent and/or slow it from crossing the blood–brain barrier and entering the brain. With a reduced amount of nicotine reaching the brain, neurotransmitter release is greatly lessened and the pleasurable, positive-reinforcing effects of nicotine are diminished. Pre-clinical studies with the vaccine have shown that vaccination slows and decreases the amount of nicotine that reaches the brain and blocks the effects of nicotine, including effects that can reinforce and maintain addiction in animals. Therefore, if a recently quit tobacco smoker is vaccinated and has a tobacco cigarette after the immunization series is completed, the antibodies generated by the vaccine bind nicotine and alter its distribution into the brain. Because not enough nicotine enters the brain, addiction-relevant neural pathways are not activated. No pleasure is derived from the tobacco cigarette and the vaccinated subject does not relapse and begin smoking again. NicVAX is administered by injection into the arm; the 3'-aminomethylnicotine molecule found in the vaccine〔 instigates an immune response in which 'nicotine' antibodies are created. The antibodies bind to nicotine molecules, causing the nicotine-antibody complexes to be too large to enter the brain; this prevents nicotine from being able to affect addiction-relevant pathways in the brain. The idea behind the drug is that since often even a single cigarette can deliver enough nicotine to the brain to reinstate the addiction, blocking the entry of nicotine into the brain might prevent this renewed dependence. This treatment works for nicotine addiction from any source. ''Clinical Pharmacology & Therapeutics'' considers this method "attractive," since the antibody does not enter the brain; as a result, side effects on the central nervous system are minimal, if any. Additionally, the antibodies produced bind only to nicotine and not to nicotine metabolites or any similar endogenous structures such as acetylcholine.〔 However, while this drug may curtail addiction, it does not prevent psychological cravings; a user could potentially smoke heavily to compensate for the nullifying effects of NicVAX.〔 However, a study performed indicated that this did not happen among the test subjects.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「NicVAX」の詳細全文を読む スポンサード リンク
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