Objectives: Bryostatin-1 is a macrocyclic lactone that has been shown to regulate protein kinase C (PKC) activity and thereby potentially inhibit tumor invasion, angiogenesis, cell adhesion, and multidrug resistance. In preclinical experiments, bryostatin-1 induces tumor growth inhibition and enhances cytotoxicity when combined with other agents including cisplatin in cervical cancer cells. It was therefore anticipated that combination bryostatin-1-cisplatin therapy would be effective in patients with cervical cancer. The current study was conducted to evaluate this therapeutic approach in patients with recurrent or advanced-stage cervical carcinoma.
Methods: An IRB-approved New York Gynecologic Oncology Group (NYGOG) trial was activated for patients with a histological diagnosis of metastatic cervical cancer or in patients with recurrent disease not eligible for surgery or radiation. Enrolled patients received bryostatin-1 (50-65 microg/m(2)) as a 1-h infusion followed by cisplatin (50 mg/m(2)). The combined treatment was administered every 21 days.
Results: Fourteen patients were enrolled. The majority of patients had squamous cell carcinoma. Ten out of fourteen patients had recurrent disease. Fifty percent of the patients received bryostatin at 50 microg/m(2) and 50% received bryostatin at 65 microg/m(2). Seventy-one percent completed two cycles of treatment. The most common grade II-III toxicities were myalgia, anemia, and nausea or vomiting. One patient developed a hypersensitivity reaction and one developed grade III nephrotoxicity. Seventy-one percent (10/14) of patients were evaluated for tumor response. Eight out of ten (80%) of patients had progressive disease and 2/10 (20%) had stable disease. There were no treatment responses.
Conclusions: Despite promising preclinical data, this clinical trial indicates that the combination of cisplatin and bryostatin-1 at the doses and schedule used is not effective in patients with advanced-stage or recurrent cervical cancer. There is even the possibility of therapeutic antagonism. The development of a serum assay for bryostatin-1 and additional mechanistic studies would be useful for future bryostatin clinical trials.