Vical Completes Enrollment and Reports Positive Interim Data in CMV Vaccine Phase 2 Trial

Vical Completes Enrollment and Reports Positive Interim Data in CMV Vaccine Phase 2 Trial

SAN DIEGO, Nov. 12 /PRNewswire-FirstCall/ -- Vical Incorporated (Nasdaq: VICL) announced today that the company has completed enrollment of subjects in a Phase 2 trial of its therapeutic DNA vaccine designed to prevent cytomegalovirus (CMV) reactivation and disease in immunosuppressed stem cell transplant recipients. An interim analysis of immunogenicity data for the first 33 transplant recipients in the recipient-only arm of the study showed significant (p<0.05) post-transplant enhancement of CMV-specific T-cell responses in subjects receiving vaccine compared with subjects receiving placebo.

"These patients are highly immunosuppressed after transplant and, due to pre-existing infection, are at risk of CMV reactivation and the associated disease," said Ronald B. Moss, M.D., Vical's Vice President of Clinical Development. "The inducement of CMV-specific T-cell responses after transplant is encouraging, as others have noted that T-cell responses may be predictive of better control of CMV reactivation and disease. These encouraging immunogenicity data should translate into clinical benefit, and should be confirmed by clinical efficacy results in the second quarter of 2009."

The company conducted an interim immunogenicity analysis on post-transplant sera from the first 47 stem cell transplant recipients (33 in the recipient-only arm and 14 in the donor-recipient arm). The resulting data were analyzed by treatment group, but clinical sites and trial participants remain blinded to individual treatment codes. The results indicated significant enhancement of CMV-specific immunity in the recipient-only arm as measured by T-cell responses to the two CMV antigens targeted by the vaccine: pp65 (p<0.05) and gB (p<0.05). Results for the donor-recipient arm were inconclusive because of the small sample size. Independent data(1) have shown that increased CMV-specific T-cell responses following stem cell transplants are predictive of favorable clinical outcome, including limited levels of active CMV and reduced CMV disease.

The Phase 2 trial included two arms. In one arm, vaccine or placebo was administered to both the donors and recipients undergoing stem cell transplants (the donor-recipient arm). In the other arm, vaccine or placebo was administered only to the stem cell transplant recipients (the recipient-only arm). The recipient-only arm of the trial recently achieved full enrollment of 80 subjects. Based on the results of the interim immunogenicity analysis, the company determined that there was no need to continue enrollment in the donor-recipient arm.

About CMV

CMV is a herpes virus that infects more than half of all adults in the United States by age 40, and is even more widespread in developing countries. While a healthy immune system typically protects an infected person against CMV disease, it rarely succeeds in completely eliminating the infection, and those whose immune systems are not fully functional are at high risk of CMV proliferation, potentially leading to severe illness or death. These include transplant patients who take immunosuppressive drugs, and fetuses and newborns of mothers who first become infected during pregnancy.

CMV infection affects 30 to 60 percent of the patients undergoing various transplant procedures, causing transplant rejection, serious illness and even death if untreated. Expensive and toxic antiviral drug therapy is used to control the disease, but does not eliminate the infection. Congenital CMV infection affects one out of every hundred infants, and causes severe consequences in about 3,600 infants and death in about 400 each year in the United States.

There is no approved vaccine against CMV. Vaccine approaches that predominantly result in antibody responses to CMV have not proven highly effective in transplant patients. Vaccine approaches using live, attenuated viruses can induce both antibody and cellular immune responses, but pose a potential safety concern, particularly for immunocompromised patients, of causing the disease they are intended to prevent. Vical's novel DNA vaccine approach is designed to induce both antibody and cellular immune responses against specific features of the CMV virus without the risk of causing CMV disease. Vical's vaccine has received orphan drug designation for hematopoietic stem cell transplant and solid organ transplant patients.

About Vical

Vical researches and develops biopharmaceutical products based on its patented DNA delivery technologies for the prevention and treatment of serious or life-threatening diseases. Potential applications of the company's DNA delivery technology include DNA vaccines for infectious diseases or cancer, in which the expressed protein is an immunogen; cancer immunotherapeutics, in which the expressed protein is an immune system stimulant; and cardiovascular therapies, in which the expressed protein is an angiogenic growth factor. The company is developing certain infectious disease vaccines and cancer therapeutics internally. In addition, the company collaborates with major pharmaceutical companies and biotechnology companies that give it access to complementary technologies or greater resources. These strategic partnerships provide the company with mutually beneficial opportunities to expand its product pipeline and address significant unmet medical needs. Additional information on Vical is available at www.vical.com [1].

This press release contains forward-looking statements subject to risks and uncertainties that could cause actual results to differ materially from those projected, including: whether Vical or others will continue development of the CMV vaccine; whether the CMV vaccine will achieve the safety and efficacy endpoints in the Phase 2 trial; whether T-cell responses will control CMV reactivation and disease; whether the interim evaluation of immunogenicity in the Phase 2 trial will be predictive of clinical benefit, and if so, whether such benefit will be confirmed with clinical efficacy results in the second quarter of 2009, if at all; whether the company will expand development of a CMV vaccine to address prevention of congenital disease, and if so, whether such results will be successful; whether Vical or its collaborative partners will seek or gain approval to market any product candidates; whether Vical or its collaborative partners will succeed in marketing any product candidates; and additional risks set forth in the company's filings with the Securities and Exchange Commission. These forward-looking statements represent the company's judgment as of the date of this release. The company disclaims, however, any intent or obligation to update these forward-looking statements.

(1) Avetisyan G, et al. Impact on the cytomegalovirus (CMV) viral load by CMV-specific T-cell immunity in recipients of allogeneic stem cell transplantation [2]. Bone Marrow Transplant. 2006 Nov;38(10):687-92.

 Avetisyan G, et al. Evaluation of intervention strategy based on CMV-specific immune responses after allogeneic SCT [3]. Bone Marrow Transplant. 2007 Nov;40(9):865-9.