Iomai Trial Shows 100 Percent Immune Response in Elderly Subjects Vaccinated With Novel Travelers' Diarrhea Patch Vaccine

GAITHERSBURG, Md., August 09, 2007 /PRNewswire-FirstCall/ -- Iomai Corporation today announced that interim results from a Phase 1 safety and immunogenicity trial of its patch-based vaccine for travelers' diarrhea found that all subjects who received the vaccine -- 19 elderly and 17 adult participants -- mounted an immune response, demonstrating that even elderly subjects with weaker immune systems respond to the vaccine.

The trial was designed to compare the number of elderly subjects (65 and older) who seroconverted -- developed antibodies to the vaccine's active ingredient -- with the number of adult participants (aged 18 to 40) who seroconverted. Because the immune system is often less powerful in older people, many vaccines do not work as well in the elderly. However, all subjects who received the Iomai patch, regardless of age, seroconverted with IgG antibodies. Moreover, 18 of 19 elderly subjects and 15 of 17 adult subjects also seroconverted with IgA antibodies. The study was conducted in Belfast, Ireland, and subjects received two patches, 21 days apart, containing "heat labile" toxin, or LT, and were followed for 42 days. No treatment- related serious adverse effects were reported.

"The results of this trial further confirm that we can effectively deliver the active ingredient in our patch-based vaccine for travelers' diarrhea to adults of all ages, and based on this data, the Iomai travelers' diarrhea vaccine could be expected to extend coverage to this important at-risk segment of the traveling population," said Gregory M. Glenn, M.D., senior vice president and chief scientific officer of Iomai. "These results, coupled with the remarkable findings from our field study that we announced last week, provide additional evidence of the significant potential for Iomai's transcutaneous immunization (TCI) approach."

Iomai last week announced that a Phase 2 field trial of the vaccine found that healthy adults who traveled to Guatemala and Mexico and were vaccinated with the Iomai patch were 75 percent less likely to suffer moderate or severe travelers' diarrhea. With the high seroconversion rates in the elderly, the interim results from this new study suggest that the protective effect of Iomai's travelers' diarrhea vaccine may apply to all adults, not just young adults. Iomai will look to confirm this in its Phase 3 trials for its travelers' diarrhea vaccine, which the company intends to launch in 2008.

The study was designed to evaluate the safety of the travelers' diarrhea vaccine patch in the elderly and it met this primary endpoint. The secondary objective included evaluation of immunogenicity of the vaccine in the elderly compared with young adults. Iomai plans to submit the study data from the trial for publication as soon as possible.

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.

ETEC, the most common cause of travelers' diarrhea, represents just under half of all cases of travelers' diarrhea for international travelers to areas where ETEC is common. A recently completed market study suggested that there is a large market for an effective ETEC vaccine, potentially exceeding $500 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.

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 predictability of the data from this trial in preventing travelers' diarrhea in the elderly, timing and expectation for Iomai commencing Phase 3 studies for this product candidate, and bringing the product candidate to market; the potential size of the market for an ETEC 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 March 31, 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.

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: August 2007

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