Chiron and Univax to Collaborate on Development of Vaccine-Based Human Immunotherapeutic Products.

EMERYVILLE, Calif., and ROCKVILLE, Md.--(BUSINESS WIRE)-- Aug. 28, 1995--Chiron Corporation (NASDAQ: CHIR) and Univax Biologics, Inc. (NASDAQ: UNVX) announced today that the two companies have signed an agreement-in-principle to create a long-term collaboration for the development of a new family of human immunotherapeutic products based on the vaccines of Chiron Biocine.

Under this agreement, Univax has exclusive worldwide rights to Chiron Biocine's vaccines for use as immunizing agents for the development of new human immunotherapeutic products. The collaboration capitalizes on the synergies from the concurrently announced proposed merger of Univax and North American Biologicals, Inc. (NABI) (NASDAQ: NBIO) in manufacturing and commercializing therapeutic human proteins (immunoglobulins, IGIV) from human plasma, together with Chiron Biocine's vaccine development capabilities and broad product pipeline.

The initial program will involve the development of a cytomegalovirus (CMV) hyperimmune globulin product to prevent and treat CMV infections. Preliminary laboratory evaluation of antibody titers in plasma of subjects immunized with Chiron Biocine's candidate CMV vaccine indicates that the plasma could contain significantly higher levels of CMV-neutralizing antibodies than currently available screened plasma. The higher levels of specific antibodies may allow the product to be administered in lower doses, with a potential for fewer side effects, shorter infusion times and improved efficacy. The higher-titer product might also allow the product to be used intramuscularly or in therapeutic areas not currently served by present products.

Chiron Biocine has completed a Phase 1 clinical trial of a CMV vaccine and based on the safety profile and immune response which were observed is planning to begin Phase 2 clinical trials. Phase 1/2 clinical trials for the CMV IGIV product are targeted by Univax to begin in 1996.

CMV, a member of the herpes virus family is widely prevalent throughout the world. Although most infections are asymptomatic, CMV causes significant clinical disease in immuno-compromised individuals, including transplant recipients and HIV-infected individuals, and is the most common cause of virus-produced birth defects (such as congenital deafness and mental retardation).

Under the collaborative agreement announced today, Univax will have an option to license each of Chiron's other vaccines, including, among others, herpes and hepatitis C vaccines, suitable for use as immunizing agents for the production of stimulated IGIV products. Univax will be responsible for all development, manufacturing and worldwide marketing of the IGIV product.

Chiron will receive milestone payments and will share in future profits. As part of the collaboration, the companies intend to explore the combination of Chiron Biocine's proprietary adjuvant, MF59, with other third-party vaccines to generate higher titer immunoglobulin products which will also be developed and marketed by Univax.

"This agreement will provide the new Univax/NABI combined entity with a pipeline of viral and bacterial vaccines and a safe, well-characterized adjuvant, which could generate a new and expanded line of efficacious antibody products," said Tom Stagnaro, president and chief executive officer of Univax. "The ideal combination of NABI's expertise in plasma collection and IGIV manufacturing, Univax's expertise in donor stimulation and development of specific polyclonal products and Chiron Biocine's expertise in vaccine development, should enable this collaboration to achieve complete product integration."

"Chiron Biocine has a broad pipeline of promising vaccine candidates, including vaccines for genital herpes, CMV and HIV in clinical trials," said Dino Dina, M.D., president of Chiron Biocine. "This collaboration will apply our vaccine and adjuvant technologies to the development and commercialization of products beyond the indications we are developing. The approach is consistent with Chiron's belief in cooperating to speed products to market and capture maximum value from its technologies."

Chiron Corporation is a diversified, science-driven healthcare company that combines diagnostic, vaccine and therapeutic strategies for managing disease. Chiron participates in four global healthcare markets: diagnostics, including immunodiagnostics, critical care diagnostics and new quantitative probe tests; therapeutics, with an emphasis on oncology and infectious disease; pediatric and adult vaccines; opthalmic surgical products for the correction of vision. Chiron also has research programs underway in gene therapy and gene transfer, combinatorial chemistry, cardiovascular disease and critical care.

Univax Biologics, Inc., founded in 1988, is a biopharmaceutical company engaged in the development and marketing of products that prevent and treat autoimmune and infectious diseases and related complications through activation and targeting of the human immune system. Univax's product pipeline includes vaccines for long-term protection and specific polyclonal antibodies for immediate, short-term protection and therapeutic intervention. Univax has begun marketing its first product, WinRho SD(TM), which recently received U.S. Food and Drug Administration regulatory clearance. Univax also has other products in clinical and preclinical development.

Concurrent with and separate from the announcement of their agreement with Chiron, Univax and NABI announced the signing of a merger agreement. The press release announcing the merger is available through NABI or Univax. The combined company will be a first-tier biopharmaceutical company and a leader in the field of high-value added antibody-based therapeutics, with annual revenues of approximately $200 million.

CONTACT: Chiron Corporation

Larry Kurtz, 510/601-2476

or

Univax Biologics

Cabot R. Caskie, 301/770-3099