- Study Designed to Demonstrate Vaccine's Effectiveness in Smoking Cessation; Results Expected Mid-2007 - ROCKVILLE, Md., May 24 /PRNewswire-FirstCall/ -- Nabi Biopharmaceuticals today announced that it has initiated a Phase IIB "proof-of-concept" study for NicVAX(R) (Nicotine Conjugate Vaccine), the company's novel, innovative and proprietary investigational vaccine being developed to treat nicotine addiction and prevent smoking relapse. The study will evaluate the effectiveness of an optimized formulation of the vaccine manufactured at commercial scale in the company's vaccine plant in Florida. The study protocol is based on consultations with U.S. and EU regulators on the design and endpoints for Phase III efficacy studies. Results from this study are expected to be announced in mid-2007. The timing of this study positions the company to be able to initiate Phase III efficacy studies in the second half of 2007. Thomas H. McLain, chairman, CEO and president, Nabi Biopharmaceuticals, stated, "This is an important milestone for Nabi Biopharmaceuticals and for the over one billion smokers in the U.S. and across the world who want to quit their addictive habit. Key elements in the design and conduct of this proof- of-concept study support our belief that NicVAX is the most advanced smoking cessation vaccine in this market. By following the expected design of Phase III efficacy trials, this study is intended to demonstrate the benefit of the optimized vaccine formulation in terms of efficacy, antibody levels and safety. Results from this study will demonstrate the quit rate we would expect from Phase III studies of the vaccine by adding other key elements in smoking cessation programs including behavioral modification and counseling. The results of this study will be important in demonstrating the vaccine's efficacy and positioning us to initiate Phase III studies in the second half of next year. It is also important to note that this study will help to evaluate an important additional benefit and differentiator with a vaccine approach to smoking cessation. We will also measure the benefit of long- lasting nicotine antibodies on preventing the high rates of relapse within the first year in smokers who have quit their habit." Henrik S. Rasmussen, M.D., Ph.D., senior vice president, clinical, medical and regulatory affairs, Nabi Biopharmaceuticals, stated, "Important new developments in smoking cessation have been very supportive of our vaccine approach. The recent approval of CHANTIX(TM) (varenicline) has provided strong support for the NicVAX mechanism of action, namely that blocking nicotine from reaching receptors inside the brain prevents the pleasurable and addictive response to smoking and thus promotes smoking cessation. We believe that our NicVAX approach will add two important advantages over a pill-based approach. First, NicVAX works by preventing nicotine from entering the brain, rather than replacing nicotine or blocking receptors with chemicals inside the brain. NicVAX works by enabling the immune system, the human body's natural defense mechanism. Second, treatment with other therapies, like CHANTIX, is stopped within a few months or the smoker can simply stop taking their therapy and be at high risk for relapse. In contrast, antibodies from NicVAX are expected to last 12 months or longer and should support getting through the critical first year in which relapse ranges as high as 95% with other therapies. A boosting schedule could also be developed for smokers who feel they continue to be at high risk for relapse after one year." Dr. Rasmussen continued, "With our intellectual property in the U.S. and Europe and the capacity to produce NicVAX in our own plant, we are in an excellent position to drive this program forward and make a real difference in the lives of millions of people afflicted with nicotine addiction." The initiation of this Phase IIB study for NicVAX is an important milestone for Nabi Biopharmaceuticals and positions the company to continue to rapidly advance this key program. This study, designed with extensive input from the U.S. Food and Drug Administration (FDA), the European Agency for the Evaluation of Medical Products (EMEA), the National Institute on Drug Abuse (NIDA) and leading external consultants, is designed to establish "proof-of- concept" and at the same time identify the optimal dose and dosing regimen for subsequent Phase III pivotal trials. By starting this study on schedule, the company expects to be well positioned to initiate Phase III clinical trials in the U.S. and Europe in the second half of 2007. During 2006, the company will also continue to advance efforts to secure external funding for the Phase III efficacy trials. In addition, the company will continue to advance efforts to establish a corporate partnership for commercialization of NicVAX. How NicVAX is Designed to Work NicVAX is designed to stimulate the immune system to produce antibodies that bind to nicotine and prevent it from entering the brain. It is believed that these nicotine antibodies will act like a "sponge" soaking up nicotine as it circulates in the bloodstream and preventing it from reaching the brain. The positive stimulus in the brain that is normally caused by nicotine is no longer present, thereby eliminating the addictive properties of nicotine and, consequently, helping people to quit. Because the ability of the body's immune system to produce these antibodies is expected to be long lasting, it is believed NicVAX will also be effective in preventing smoking relapse, a significant challenge with existing smoking cessation therapies. This is an important differentiator between NicVAX and existing anti-smoking treatment modalities. By preventing the pleasurable response ("the rush") that occurs when nicotine reaches the brain, NicVAX takes away what is believed to be the main reason that most people cannot stop smoking. Development Progress to Date Early clinical data indicates that NicVAX, if approved, could potentially be one of the most efficacious smoking cessation products available. In a Phase II clinical trial, NicVAX achieved a 33 to 40 percent quit rate in smokers who received the highest dose level versus nine percent in the placebo group. These results represented a vaccine-only effect, as patients were not given any supplemental treatments, behavioral support or counseling. It is expected that the response rate would be further improved as behavioral support and counseling are built into the program. In March 2006, Nabi Biopharmaceuticals announced that NicVAX had received Fast Track Designation from the FDA, which facilitates the development of products that treat serious diseases where an unmet medical need exists. In January 2006, the company announced that a new formulation of NicVAX with less vaccine adjuvant was safe and produced high levels of antibodies to nicotine in smokers. Importantly, antibody levels were consistent with a vaccine with higher adjuvant levels that demonstrated up to a 40 percent success rate in smoking cessation in an earlier Phase II trial. Both vaccine formulations are being evaluated in the Phase II "proof-of-concept" study initiated in May 2006. In September 2005, the company announced that it had received a $4.1 million grant from NIDA, part of the National Institutes of Health, which is expected to fully offset the external costs of the Phase II "proof-of-concept" clinical study. NIDA has contributed scientific and clinical expertise to the program and has funded the costs for toxicology testing and earlier clinical trials in the U.S. Nabi Biopharmaceuticals' intellectual property portfolio for technology related to NicVAX includes both issued and pending patents in the U.S. In addition, the company holds granted patents in 18 European countries, plus patents and pending patent applications in numerous other countries around the world. About the Phase IIB Study The Phase IIB study for NicVAX is a double-blinded, placebo-controlled dose ranging study comprised of approximately 300 patients, a large enough sample size to establish both "proof-of-concept" and optimal dose identification for the Phase III program. The primary endpoint of the study is the abstinence rate at six months. Abstinence will be evaluated by several measures, including reported cigarette consumption, chemical markers of nicotine in the bloodstream, and behavioral assessment. Secondary endpoints include the abstinence rate at 12 months, total cigarette consumption, titer levels, safety and nicotine dependency. Study results from the initial six months assessment, which include the primary endpoint, are anticipated in mid- year 2007. The efficacy rates in this study will incorporate the benefits of other elements in smoking cessation programs, including counseling and behavioral modification. A previous Phase II study which demonstrated up to a 40 percent quit rate in smokers evaluated the vaccine-only benefits of NicVAX. Cigarette Smoking: A Growing Global Health Challenge Smoking is a global healthcare problem, and The World Health Organization estimates that there are 1.3 billion smokers worldwide and nearly five million tobacco-related deaths each year. According to the U.S. Centers for Disease Control and Prevention (CDC), tobacco use is the single leading preventable cause of death in the U.S. and is responsible for more than 440,000 deaths each year. They estimate that approximately 70 - 80 percent of smokers in the U.S. want to quit, but less than five percent of those who try to quit remain smoke-free at 12 months. In addition, they estimate that smoking accounts for $167 billion in healthcare expenditures and productivity losses each year.(1) To learn more about NicVAX and how it works, please visit our Web site at: http://www.nabi.com/pipeline/pipeline.php?id=3 . About Nabi Biopharmaceuticals Nabi Biopharmaceuticals leverages its experience and knowledge in powering the immune system to develop and market products that fight serious medical conditions. The company has three products on the market today: PhosLo(R) (calcium acetate), Nabi-HB(R) [Hepatitis B Immune Globulin (Human)], and Aloprim(TM) (allopurinol sodium) for Injection. Nabi Biopharmaceuticals is focused on developing products that address unmet medical needs and offer commercial opportunities in our core business areas: Gram-positive bacterial infections, hepatitis and transplant, kidney disease (nephrology) and nicotine addiction. For a complete list of pipeline products, please go to: http://www.nabi.com/pipeline/index.php . The company is headquartered in Boca Raton, Florida. For additional information about Nabi Biopharmaceuticals, please visit our Web site at: http://www.nabi.com/ . Forward-Looking Statement Statements in this press release about the company that are not strictly historical are forward-looking statements and include statements about our products in development, the market for such products, and clinical trials and studies. You can identify these forward-looking statements because they involve our expectations, beliefs, intentions, plans, projections, or other characterizations of future events or circumstances. These forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that may cause actual results to differ materially from those in the forward-looking statements as a result of any number of factors. These factors include, but are not limited to, risks relating to the company's ability to advance the development of products currently in the pipeline or in clinical trials; maintain the human and financial resources to commercialize current products and bring to market products in development; obtain regulatory approval for its products in the U.S., Europe or other markets; successfully develop, manufacture and market its products; successfully partner with other companies; realize future sales growth for its biopharmaceutical products; maintain sufficient intellectual property protection; raise additional capital on acceptable terms; and re-pay its outstanding convertible senior notes when due. Many of these factors are more fully discussed, as are other factors, in the company's Annual Report on Form 10-K for the fiscal year ended December 31, 2005 and Quarterly Report on Form 10-Q for the Quarter ended April 1, 2006 filed with the Securities and Exchange Commission. 1. American Cancer Society, Cancer Prevention & Early Detection Facts & Figures 2006. Atlanta: American Cancer Society, 2006. Centers for Disease Control and Prevention. Annual smoking - attributable mortality, years of potential life lost, and productivity losses - United States, 1997-2001. MMWR Morb Mortality Weekly Rep. 2005;54(25); 625:628. DATASOURCE: Nabi Biopharmaceuticals CONTACT: Thomas E. Rathjen, Vice President, Investor Relations, Nabi Biopharmaceuticals, +1-561-989-5800 Web site: http://www.nabi.com/ http://www.nabi.com/pipeline/index.php

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