VICAL CONFIRMS ACTIVITY OF ALLOVECTIN-7 IN MELANOMA AND HEAD/NECK CANCER.

DENVER, CO--(BUSINESS WIRE)--May 17, 1997--

Clinical Trial Results Presented At ASCO Meeting

Vical Incorporated (Nasdaq:VICL) announced today that initial Phase II data for Allovectin-7, the Company's lead oncology product candidate, indicate potential efficacy in certain patients with advanced melanoma. Preliminary results from a separate Phase I/II trial indicated potential efficacy in certain patients with inoperable head and neck cancer. Results from both trials were presented at the annual meeting of the American Society of Clinical Oncology.

Although all melanoma patients enrolled in the multi-center Phase II clinical trial with Allovectin-7 had advanced metastatic disease, initial results further suggest that the potential treatment may be more effective in patients with advanced regional disease than in patients with widespread disease affecting multiple internal organs. Alain B. Schreiber, M.D., Vical's President and CEO, said, "These results support our decision to perform studies focused on melanoma, and suggest a clear strategy for development of an initial product indication. We now have information that may allow us to target the melanoma patient population most likely to benefit from Allovectin-7."

Allovectin-7

Allovectin-7 is a novel, gene-based product candidate being studied in melanoma and other types of cancer. The active ingredient in Allovectin-7 is a gene encoding HLA-B7, an antigen responsible for strong immune responses such as organ transplant rejection. To improve delivery, the gene is complexed with a proprietary lipid and suspended in a water-based solution. Administration occurs by direct injection into a tumor, leading to uptake by the tumor cells and subsequent expression of the HLA-B7 antigen. The Company expects the expression of HLA-B7 by cancer cells may trigger the patient's immune system to recognize these cells as "foreign" and selectively destroy the tumor. As a result of Phase I/II clinical testing of Allovectin-7 in several cancer indications, completed in 1995, Vical concluded that the product candidate was safe and well-tolerated, successful in delivering the HLA-B7 gene in a majority of patients, and effective in inducing tumor shrinkage in some patients.

Multi-center Phase II trials of Allovectin-7 began in September 1995, studying five different cancer indications in about 20 patients each. In October 1996, Vical initiated an additional multi-center trial in which approximately 40 patients with advanced metastatic melanoma are currently being enrolled and treated. Several additional Phase I/II trials are ongoing, studying Allovectin-7 either alone or in combination with other agents in various cancer indications.

Allovectin-7 in Melanoma

Vical's Allovectin-7 melanoma trials to date have been conducted in Stage IV patients who have failed to respond to chemotherapy or radiation treatments. Phase I/II Allovectin-7 trials resulted in significant (greater than or equal to 50%) local tumor shrinkage in 13 of 36 melanoma patients. Seven patients were considered partial clinical responses, and one of the seven attained a complete response and remains tumor-free more than 33 months later. -0-

Allovectin-7 Phase I/II Results in Melanoma

Disease     Patients     Local     Partial     Complete     Duration
Progression             Response   Clinical    Clinical
                                   Response    Response

Stage IV       36          13         6           1        8-33 months
                                                        and continuing

Preliminary Phase II results confirmed the potential efficacy of Allovectin-7 in treating melanoma patients, and suggested a correlation between disease spread and such potential efficacy. Among 11 melanoma patients with advanced disease involving the skin or underlying tissue, regional lymph nodes, and no more than one other internal organ, 5 patients exhibited tumor shrinkage with 3 of those characterized as partial clinical responses. In 16 patients with widespread advanced disease affecting multiple internal organs, only 1 exhibited tumor shrinkage. -0-

Initial Allovectin-7 Phase II Results in Melanoma

Disease     Patients     Local     Partial     Complete     Duration
Progression             Response   Clinical    Clinical
                                   Response    Response

Stage IV
limited to
cutaneous      11          5           3           0       4-10 months
region or                                                      and
lymph nodes                                                continuing

Stage IV
affecting
multiple       16          1           0           0           --
internal
organs

Allovectin-7 in Other Indications

Preliminary data from Phase II trials in the other four indications studied showed mixed results. In renal cell carcinoma, 8 of 25 patients had stable disease from 4 to 13 months after treatment, and they continue to be monitored. Patients with breast cancer and non-Hodgkin's lymphoma remain under study, as preliminary data were insufficient to suggest any conclusions. Among 23 patients with advanced colorectal cancer, no responses were noted.

Allovectin-7 in Head and Neck Cancer

Allovectin-7 is also being evaluated in a separate Phase I/II trial for patients with advanced, inoperable or recurrent post-surgical head and neck cancers. Of the eight patients treated to date, three have achieved partial clinical responses, two considered near-complete. Patient accrual and treatment are ongoing. -0-

Initial Allovectin-7 Phase I/II Results in Head & Neck Cancer

Disease     Patients     Local     Partial     Near-       Duration
Progression             Response   Clinical    Complete
                                   Response    Response

Inoperable                                                 4-16 months
Stage III      8           3          1           2           and
or IV                                                      continuing

Schreiber said, "The positive early results with Allovectin-7 in treating advanced head and neck cancers certainly warrant further study. The emerging pattern of potential product activity in melanoma patients is encouraging."

Melanoma Background

Melanoma is a skin cancer found predominantly in Caucasians, most often in fair-skinned people susceptible to sunburn. Exposure to sunlight, particularly UVB rays, is considered the primary cause. The incidence of melanoma is doubling every 6 to 10 years among affected populations, with more than 40,000 new cases annually and 7,000 deaths estimated for 1997 in the United States.

If detected in Stages I and II, defined as localized disease of varying diameter and thickness, melanoma often can be successfully treated by surgical removal. The five-year survival rate for localized malignant melanoma, if treated, is about 95 percent.

If untreated, melanoma spreads to tissues beneath the skin and to internal organs, most often the lymph glands, lungs, brain, or liver. If the disease progresses to Stage III, defined as limited regional metastases, treatment may involve surgical removal of the tumors and any affected lymph glands, followed by systemic or local chemotherapy with single or multiple agents. The five-year survival rate for treated Stage III patients is about 60 percent, and quality of life is compromised by both the disease and the treatment.

If the disease progresses to Stage IV, defined as advanced regional or any distant metastases, treatment may include surgical removal of tumors and affected lymph glands, systemic or local chemotherapy, radiation therapy, and immunotherapy. The prognosis is poor, with a five-year survival rate for treated Stage IV patients of about 15 percent and a severely impaired quality of life.

Head and Neck Cancer Background

Head and neck cancer describes any of several localized tumors affecting the oral cavity, the pharynx or larynx, or the esophagus. Head and neck cancers are found more frequently in men than in women, and most often in men over age 40. Risk factors vary with the particular location, but can include use of tobacco and excessive consumption of alcohol. New diagnoses in the United States for the various head and neck cancers total more than 50,000 new cases annually and more than 20,000 deaths are estimated for 1997.

Most head and neck cancers are treated by surgical removal and/or localized radiation therapy, with widely ranging degrees of success depending on the number of tumors, their size, and their specific location. In advanced disease, standard treatment may be preceded by systemic chemotherapy to improve treatability, or followed by systemic chemotherapy to address remaining cancer cells, most often with a combination of agents. The five-year survival rate for head and neck cancer patients, if treated, varies from more than 90 percent for localized, accessible disease to less than 5 percent for widespread, inoperable malignancies.

Vical Incorporated is focused on the development of gene-based pharmaceutical product candidates for human therapy. Vical's gene-based therapeutic approach may offer safer and more cost-effective alternatives for many diseases, including cancer, infectious diseases and metabolic disorders.

This press release contains forward-looking statements that are subject to risks and uncertainties that could cause actual results to differ materially from those set forth in the forward-looking statements, including whether any product candidates will be shown to be safe and efficacious in clinical trials, the timing of clinical trials, and additional risks set forth in the Company's filings with the Securities and Exchange Commission. Actual results may differ materially from those projected. 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.

CONTACT: Alan R. Engbring

Director, Investor Relations

Vical Incorporated

[phone]