Like smoke from a cigarette, Nabi Biopharmaceuticals Inc.'s stock rose steadily on Tuesday following news that its nicotine conjugate vaccine at its highest dose helped 33 percent of smokers quit the habit.
The stock (NASDAQ:NABI) climbed $1.79, or 15.3 percent, to close at $13.48, following the release of the positive Phase II data for NicVAX, which is being developed to prevent and treat nicotine addiction by acting as an aid to smoking cessation.
"The results that we saw in the Phase II study were actually better than what we had hoped," said Thomas McLain, chairman, president and CEO of Nabi. "In context, this was a vaccine-only approach. There's usually psychological counseling and other measures in convincing the subjects that they need to quit. We did none of that here."
The 33 percent quit rate was in smokers who received NicVAX at the highest dose level of 200 micrograms. The placebo group had a 9 percent rate. Patients in the study were given NicVAX without any supplemental treatments, behavioral support or counseling.
Nabi plans to talk with regulatory authorities about the future development path for NicVAX. But McLain said the plan is to move into another Phase II trial in Europe, then enter a Phase III trial in the second half of 2005. The European trial will look at NicVAX at the 200-microgram dose and higher, possibly 300-microgram and 400-microgram doses.
"Because we saw at the 200-microgram dose that it was safe and well tolerated," McLain told BioWorld Today, "we actually think that we may at higher doses be capable of even a greater reduction or a greater quit rate."
NicVAX is designed to cause the immune system to produce antibodies that bind to nicotine and prevent it from entering the brain, thereby preventing the positive stimulus - the "rush" - that occurs when nicotine binds to receptors. The rush is what researchers believe make it difficult for smokers to quit.
The double-blind, placebo-controlled, randomized Phase II study had set out to assess safety and antibody response, as well as standard measures of anti-smoking efficacy, such as the percentage of patients who quit smoking. It was conducted at three sites across the U.S. and enrolled 68 smokers who were randomized to receive a series of up to four injections containing either NicVAX or placebo. The placebo and NicVAX, which was dosed at 50, 100 or 200 micrograms, were given on days 0, 28, 56 and 182. Smokers who were considered to have "quit" were those that did not smoke for at least 30 consecutive days.
"When you look at the data, we didn't just take the patient's word for it," McLain said.
Researchers confirmed the smoking cessation by checking cotinine and carbon monoxide levels. Results from the study also showed a substantial reduction in average cigarette consumption and nicotine dependence in smokers who received the highest dose of NicVAX vs. lower doses or placebo. NicVAX was well tolerated and the side effects were similar between the active dose levels and the placebo group.
Nabi expects to present full data from the study at medical meetings in 2005.
NicVAX uses Nabi's conjugate vaccine technology to help the body's immune system recognize and deal with problems it might otherwise ignore. That technology also is used in StaphVAX, Nabi's Phase III product designed to prevent S. aureus infections in patients in the hospital or other treatment centers. The company expects to submit a biologics license application in 2005.
With NicVAX, nicotine antibodies act like a sponge, soaking up nicotine as it circulates in the bloodstream, preventing it from reaching the brain. Nabi initiated a Phase I/II placebo-controlled, double-blind trial in January 2003, which showed that multiple injections of NicVAX were safe, well tolerated and resulted in an immune response that generated substantial amounts of nicotine-specific antibodies.
The World Health Organization estimates that there are 1.3 billion smokers worldwide and about 5 million tobacco-related deaths each year. In the U.S., about 46 million adults and 3 million high school students smoke. According to the Centers for Disease Control and Prevention, about 70 percent of U.S. smokers want to quit, but less than 5 percent of those who try are able to abstain from smoking for more than 12 months.
In addition to NicVAX and StaphVAX, Nabi is developing an antibody called Altastaph to prevent and treat S. auerus infections, and an antibody called Civacir to prevent hepatitis C virus re-infection in liver transplant patients. The company has four marketed products: PhosLo for hyperphosphatemia; Nabi-HB for hepatitis B; WinRho SDF for immune thrombocytopenic purpura and suppression of RH isoimmunization; and Aloprim for leukemia, lymphoma and solid-tumor malignancies.
The company's sales force is directed toward hospitals, so McLain expects to partner NicVAX following Phase III trials.
A grant from the National Institute on Drug Abuse of the National Institutes of Health covered the outside clinical costs for the Phase II trial.
"We're hopeful that they will also be able to fund the European trial and the Phase III," McLain said.