Cell Genesys Inc presented clinical data from an exploratory phase 2 clinical trial of GVAX pancreatic cancer vaccine in patients with inoperable, metastatic pancreatic cancer. The company also updated the status of a parallel phase 2 trial in patients with operable pancreatic cancer who receive the vaccine after surgery, an approach which continues to be the focus of the company's GVAX pancreatic cancer vaccine programme.
These two trials were prompted by encouraging results from an earlier phase 1 clinical trial in operable patients which demonstrated prolonged, disease-free survival of at least six years in three of eight patients treated at therapeutic dose levels.
The new findings were presented by Daniel Laheru, assistant professor of medical oncology at Johns Hopkins Kimmel Cancer Centre, and colleagues, at the annual meeting of the Lustgarten Foundation for Pancreatic Cancer Research, which was sponsored by the American Association of Cancer Research and held this past weekend in San Francisco, CA.
The phase 2 trial in patients with inoperable pancreatic cancer enrolled 50 patients, the majority of whom had failed at least two prior chemotherapy regimens. Patients were divided into two cohorts, both receiving up to six doses of GVAX pancreatic cancer vaccine at 21-day intervals. Cohort A (30 patients) received GVAX pancreatic cancer vaccine alone, and cohort B (20 patients) received GVAX pancreatic cancer vaccine in combination with low-dose cyclophosphamide, a chemotherapeutic agent which has been shown in the subtherapeutic doses administered to enhance the immune response by reducing "suppressor" T lymphocyte function in the absence of a direct anticancer effect.
Despite the very advanced stage and extensive prior chemotherapy in the majority of patients, there was a trend toward an improved outcome with combination therapy in cohort B by all measures of clinical activity. Forty per cent of patients in cohort B demonstrated stable disease, compared with 16.7 per cent in cohort A. Moreover, the median time to progression was 57 days in cohort B and 42 days in cohort A, and median survival in cohort B was 4.3 months compared with 2.3 months in cohort A. In addition, there was a correlation between survival and the patients' post-vaccination blood level of GM-CSF produced by GVAX pancreatic vaccine. Median survival was 5.3 months for patients above the median peak level and 1.8 months for patients below that level (p=0.03). Treatment with GVAX pancreatic cancer vaccine with or without cyclophosphamide was generally well tolerated.
In other news, the company reported the status of enrolment for the second phase 2 trial in patients with operable pancreatic cancer who receive the vaccine after surgical resection of their tumour and adjuvant radiation chemotherapy. This study, which is being conducted at Johns Hopkins Kimmel Cancer Centre, has enrolled more than 45 out of a projected 60 patients. Enrolment is expected to be completed this year and preliminary data may be available during 2005.
"The results reported from our trial in inoperable pancreatic cancer demonstrate the safety and feasibility of administering GVAX pancreatic cancer vaccine in combination with low dose cyclophosphamide chemotherapy and suggest that this combination may have enhanced clinical activity even in patients with the most advanced stage of this highly aggressive cancer," stated Joseph J Vallner, president and chief operating officer of Cell Genesys.
Pancreatic cancer is the fourth leading cause of cancer death in the United States. According to the American Cancer Society, in 2004, an estimated 31,860 Americans will be diagnosed with pancreatic cancer and approximately 31,270 Americans will die from the disease.