Iomai Patch-Based Vaccine Cut Rate of Travelers' Diarrhea by 75 Percent in Phase 2 Field Study

Statistically Significant Data Detailed at a Late-Breaking Presentation at ICAAC Meeting

CHICAGO and GAITHERSBURG, Md., September 18, 2007 /PRNewswire-FirstCall/ -- Iomai Corporation today announced that travelers who received the company's patch-based travelers' diarrhea vaccine were significantly less likely to be sickened as compared with travelers who receive a placebo, according to research presented today by Chief Scientific Officer Gregory Glenn, M.D. at a late-breaker presentation during the "Vaccines and Pediatric Infections" session of the 47th Interscience Conference on Antimicrobial Agents and Chemotherapy being held in Chicago.

"We have demonstrated that vaccinated travelers can dramatically cut their risk of diarrhea by using our needle-free patch," said Dr. Glenn, Iomai's founder. "Those who received the Iomai vaccination were much less likely to get sick, and those who were sickened had far milder illness than those who received a placebo. These are clinically significant results that suggest that the patch vaccine will address the most significant unmet need for travel medicine: prophylaxis for travelers' diarrhea."

The study found that of the 59 individuals who received the novel, patch-based vaccine, only three suffered moderate or severe diarrhea, while 23 of the 111 who received a placebo suffered moderate or severe diarrhea, a 75 percent reduction (p=0.007). One of the 59 volunteers in the vaccine group reported severe diarrhea, compared with 12 of the 111 in the placebo group, an 84 percent reduction (p=0.033).

"The results presented at ICAAC are the most robust ever shown in the prevention of travelers' diarrhea, and they suggest we may be near a turning point in the prevention of this common, often-serious disease," said Herbert L. DuPont, M.D., professor and director of the Center for Infectious Diseases at The University of Texas School of Public Health and the principal investigator on the trial. "If Phase 3 trials for the vaccine validate these results, those of us in travel medicine will have an excellent new weapon in our arsenal."

The research was conducted in collaboration with researchers from the Johns Hopkins Bloomberg School of Public Health and the University of Texas School of Public Health.

Iomai plans to begin a Phase 3 program for the needle-free vaccine patch vaccine in 2008.

"We are moving this product ahead as quickly as possible," said Chief Executive Officer Stanley C. Erck. "This is a pressing, unmet medical need. Travelers' diarrhea is the most common travel ailment in the world, yet there are no effective vaccines available for the condition. A recently completed market study suggests that there is a $750 million market for effective protection against travelers' diarrhea, an opportunity that we are well-positioned to target."

About the Phase 2 Trek Study

The Trek Study followed 170 travelers to Mexico and Guatemala. Each volunteer received either two doses of the Iomai vaccine patch or a placebo, 2 to 3 weeks apart, with the last dose administered a week before travel. Travelers kept detailed diaries and received in-country checkups. The study met its primary endpoints, which were designed to evaluate the safety of the vaccine and the incidence of enterotoxigenic E. coli (ETEC) bacteria -- the most common cause of travelers' diarrhea. No vaccine-related serious adverse events were reported.

Of the few vaccinated patients who were sickened, the diarrhea lasted only half a day on average, while those in the placebo group endured two days of illness and more than twice as many loose stools. Although not statistically significant, the frequency of new-onset irritable bowel syndrome, a long-term consequence of travelers' diarrhea, was three times greater in placebo than vaccine recipients.

Iomai's vaccine uses an ETEC toxin delivered via a skin patch using the company's novel transcutaneous immunization (TCI) technology. ETEC causes illness through the toxins it produces, including one known as heat-labile toxin or LT. Iomai's unique patch-based vaccine enables the safe administration of this potent immunogen into the skin to stimulate the immune response.

About Travelers' Diarrhea

This year, approximately 55 million international travelers will visit countries where bacteria that cause travelers' diarrhea are endemic, particularly Africa, Asia and Latin America, and about 20 million of those travelers will develop travelers' diarrhea.

A recently completed market study suggested that there is a large market for an effective travelers' diarrhea vaccine, potentially exceeding $750 million annually. If approved, the Iomai vaccine would be the first vaccine for travelers' diarrhea available in the United States.

ETEC's impact goes beyond travelers. The World Health Organization estimates that children in the developing world suffer 210 million episodes of diarrhea caused by ETEC annually, causing 380,000 deaths each year.

ABOUT IOMAI CORPORATION

Iomai Corporation discovers and develops vaccines and immune system stimulants, delivered via a novel, needle-free technology called transcutaneous immunization (TCI). TCI, discovered by researchers at the Walter Reed Army Institute of Research, taps into the unique benefits of a major group of antigen-presenting cells found in the outer layers of the skin (Langerhans cells) to generate an enhanced immune response. Iomai is leveraging TCI to enhance the efficacy of existing vaccines, develop new vaccines that are viable only through transcutaneous administration and expand the global vaccine market. Iomai currently has four product candidates in development: three targeting influenza and pandemic flu and one to prevent travelers' diarrhea. For more information on Iomai, please visit http://www.iomai.com.

Some matters discussed in this press release constitute "forward-looking statements" that involve known and unknown risks and uncertainties that could cause actual results to differ materially from those expressed or implied by the forward-looking statements. Such forward-looking statements include statements about the patch vaccine being a prophylaxis for travelers' diarrhea, the timing for commencing Phase 3 studies, and bringing the product candidate to market; the potential size of the market for a travelers' diarrhea vaccine; the applicability of TCI technology to other pathogens; and that, if approved, Iomai's vaccine would be the first available in the U.S. Applicable risks and uncertainties include, among others, that Iomai may not be able to enroll sufficient numbers of patients in future clinical trials; that future clinical trials may not replicate results seen in the trial described in this press release; that Iomai may be unable to obtain the regulatory approvals necessary to conduct additional clinical trials or to market any product for travelers' diarrhea; that estimates of market size overstate the number of travelers who would use such a product, if it were approved; that competitors may develop products that are safer, more effective, or more convenient to use; and the risks identified under the heading "Factors That May Impact Future Results" in Management's Discussion and Analysis of Financial Condition and Results of Operations in Iomai's Quarterly Report on Form 10-Q for the three months ended June 30, 2007, and filed with the Securities and Exchange Commission. While Iomai believes that this product candidate is amenable to self-administration, in the Phase 2 study described in this press release, medical professionals administered the vaccine. Whether any approved product would be self-administered would depend on many factors, including the outcome of any studies the Company conducts evaluating self-administration and the views of regulatory agencies. Iomai cautions investors and others not to place undue reliance on the forward-looking statements contained in this press release. Iomai's business is subject to many risks. For a discussion of such risks, you are encouraged to read the documents the Company files with the U.S. Securities and Exchange Commission, available at http://www.sec.gov. The statements in this press release speak only as of the date of this document, and Iomai undertakes no obligation to update or revise the statements.

Posted: September 2007

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