Chiron And DepoTech Announce Phase 3 Clinical Trial Results and Start of Phase 4 Study of DepoCyt.

EMERYVILLE/SAN DIEGO, Calif.--(BUSINESS WIRE)---June 25, 1996-- Chiron Corporation (NASDAQ:CHIR) and DepoTech Corporation (NASDAQ:DEPO) today announced that results of a Phase 3 clinical trial of DepoCyt(TM), an anti-cancer therapeutic, showed a higher response rate versus the current standard of therapy in patients with neoplastic meningitis (NM) arising from solid tumors.

Neoplastic meningitis occurs when metastases from solid tumors, leukemia, or lymphoma spread to the tissue surrounding the brain and spinal cord. Of the approximately 65,000 cancer patients who are afflicted with this disease annually in the U.S., most have NM arising from solid tumors. Conventional therapy requires frequent, repeated injections and has limited efficacy.

The response rate was a primary endpoint of a multicenter, controlled, non-blinded trial of DepoCyt in which 61 patients were randomized to treatment either with DepoCyt or methotrexate, a generic chemotherapy agent that is the current standard of care for NM arising from solid tumors. Fifty-four of these patients were evaluable for the analysis of response to therapy.

Response in this study was defined as the absence of malignant cells in two consecutive samples of cerebrospinal fluid taken from patients and lack of disease progression as assessed through neurological evaluation. Of the 25 evaluable patients treated with DepoCyt, 36 percent showed a complete response versus 17 percent of 29 evaluable patients treated with methotrexate. The study design did not include an evaluation of partial response.

Additionally, because previous studies have shown that methotrexate has a better response rate in NM arising from breast and small cell lung cancers compared to other types of solid tumor metastases, patients entering the study were stratified into two subgroups and randomized to treatment either with DepoCyt or methotrexate. In the breast and small cell lung cancer (SCLC) subgroup, of eight evaluable patients treated with DepoCyt, 38 percent showed complete response versus 25 percent of 12 evaluable patients treated with methotrexate. In the subgroup made up of all other solid tumor cancers, of 17 evaluable patients receiving DepoCyt, 35 percent responded versus 12 percent of 17 evaluable patients treated with methotrexate.

DepoCyt is an injectable, sustained-release formulation of the chemotherapeutic agent cytarabine encapsulated in DepoFoam(TM), DepoTech's proprietary lipid-based drug delivery technology. In the solid tumor arm of the Phase 3 trial, patients received a dose of DepoCyt every 14 days, compared to twice per week dosing with methotrexate.

"These results confirm earlier data that DepoCyt may be an important new therapy for patients with NM," said Edward L. Erickson, president and chief executive officer of DepoTech. "Based on these data and other study end points from solid tumor patients, DepoTech and Chiron plan to file regulatory submissions with the U.S. Food and Drug Administration (FDA) and the Canadian Health Protection Board (HPB)."

"Based on the clinical results, DepoCyt appears to represent a substantial therapeutic advance in this difficult-to-treat cancer," said Edward Kenney, head of Chiron Therapeutics. "If approved, DepoCyt will complement other Chiron Therapeutics products currently used in the treatment of solid-tumor cancers."

Chiron and DepoTech plan to continue to follow patients still on study and release additional trial results in the coming months related to other defined endpoints, such as quality of life, duration of response and mortality. Furthermore, pivotal studies of DepoCyt in NM arising from lymphomas and leukemias are continuing.

Separately, Chiron and DepoTech announced the start of a multicenter Phase 4 study of DepoCyt for the treatment of NM arising from solid tumors in the U.S. and Canada. This study is a non-randomized trial intended to collect further data relating to safety and efficacy. The study also permits additional injections of DepoCyt for patients who fail to respond completely during the initial induction period of the study or who relapse 30 days following completion of the treatment protocol.

DepoCyt will be marketed by Chiron in the U.S., Canada and Europe, and manufactured by DepoTech in its San Diego production facilities. Chiron is currently conducting a clinical trial of DepoCyt in Europe.

Chiron Corporation is a science-driven healthcare company that combines diagnostic, vaccine, and therapeutic strategies for controlling 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; and ophthalmic surgical products for the correction of vision. Chiron also has research programs underway in gene therapy, combinatorial chemistry, cancer, infectious and cardiovascular disease and critical care.

DepoTech Corporation is a drug delivery company engaged in the development and manufacture of sustained-release therapeutic products based on DepoFoam.

This press release contains forward-looking statements regarding DepoTech and Chiron. Actual results could differ materially from those described in this press release as a result of a number of factors, including, but not limited to the following: There can be no assurance that any product in the DepoTech and Chiron collaborative product pipeline will be successfully developed or manufactured, or that final results of human clinical trials will be supportive of regulatory approvals required to market products, or that patient and physician acceptance of these products will be achieved.

CONTACT: Chiron Corp., Emeryville

Larry Kurtz, 510/601-2476

or

DepoTech Corporation, San Diego

Edward L. Erickson, 619/625-2424