Thymidine kinase gene therapy with concomitant topotecan chemotherapy for recurrent ovarian cancer Annette Hasenburg, 1,2 Xiao-Wen Tong, 1,2 Augusto Rojas-Martinez, 3 Cassandra Nyberg-Hoffman, 3 Christina C. Kieback, 2 Alan Kaplan, 2 Raymond H. Kaufman, 2 Ibrahim Ramzy, 4 Estuardo Aguilar-Cordova, 3 and Dirk G. Kieback 1,2 1 Department of Obstetrics and Gynecology, Freiburg University Medical Center, Freiburg, Germany; Departments of 2 Obstetrics and Gynecology, 3 Pediatrics/Hematology-Oncology, and 4 Pathology, Baylor College of Medicine, Houston, Texas 77030. Introduction: Patients with recurrent ovarian cancer were treated with a replication-deficient recombinant adenovirus containing the herpes simplex virus thymidine kinase gene administered intraperitoneally (i.p.) followed by administration of an anti-herpetic prodrug and topotecan. Materials and Methods: A total of 10 patients with stage IIIc epithelial ovarian cancer underwent secondary debulking to 0.5 cm residual tumor. Patients with normal i.p. flow received i.p. delivery of adenovirus. Two patients each were treated on dose level 1 (2  10 10 vector particles (VP)), dose level 2 (2  10 11 VP), and dose level 3 (2  10 12 VP); four patients were treated on dose level 4 (2  10 13 VP). Acyclovir and topotecan were started 24 hours after vector delivery. Results: No patient treated at any dose level incurred unanticipated toxic effects, and all side effects resolved. The most common adverse event was myelosuppression: grade 3 or 4 thrombocytopenia with grade 2– 4 anemia in three patients and grade 3 or 4 neutropenia in eight patients. Three patients developed thrombocytosis and three patients had a mild elevation of serum glutamic pyruvic transaminase/alanine aminotransferase. Temperature elevations that were not associated with detectable infection occurred in two patients. Discussion: I.p. delivery of adenoviral vector with concomitant topotecan chemotherapy was well tolerated without significant lasting toxicities. Side effects were independent of the dose of adenoviral vector. Cancer Gene Therapy (2000) 7, 839 – 852 Key words: Ovarian cancer; thymidine kinase; gene therapy; intraperitoneal therapy; acyclovir; topotecan. O varian cancer is the leading cause of death from gynecological cancer, with an overall 5-year survival rate of 28% to 35%. In the United States alone there are 19,000 new cases and 12,000 deaths from ovarian cancer each year. 1 The estimated number of cases worldwide is 140,000. 2 The initial chemotherapy for ovarian cancer usually includes the drugs cisplatin or carboplatin in a regimen combined with paclitaxel or cyclophosphamide. Up to 73% of patients with stage III and IV tumors respond to this therapy. 3 However, this initial treatment response does not translate into a favorable long-term prognosis; only 4 –25% of treated patients who had stage III and IV ovarian cancer are alive and disease-free at 5 years. 4 Considering these poor patient outcomes, alternative therapeutic approaches are necessary to improve the long-term survival of patients with ovarian cancer. The phase I study described here was designed to evaluate the safety and toxicity profile of intraperitoneal (i.p.) gene therapy (GT) for patients with locally recur- rent ovarian cancer after failure of combined radical surgery and chemotherapy. Patients with this profile do not have any standard treatment available to them that demonstrates a high degree of efficacy in eradicating the tumor with a reasonable degree of safety. GT mechanism The proposed strategy involves transduction of tumor cells by an adenoviral vector carrying the herpes simplex virus thymidine kinase (HSV-tk) gene (ADV- HSV-tk), which mediates sensitization to the antiviral drug acyclovir (ACV). The viral enzyme ADV-tk metabolizes ACV to a monophosphate, and the hu- man enzyme completes the activation to a triphos- phate. The phosphorylated ACV is incorporated into nascent DNA chains of proliferating cells and acts as Received August 26, 1999; accepted December 19, 1999. Address correspondence and reprint requests to Dr. Dirk G. Kieback, Department of Obstetrics and Gynecology 1, Freiburg University Medical Center, Hugstetter Strasse 55, D-79106 Freiburg/Brsg., Germany. E-mail address: dKieback@frk1.ukl.uni-freiburg.de Cancer Gene Therapy, Vol 7, No 6, 2000: pp 839–852 839 © 2000 Nature America, Inc. 0929-1903/00/$15.00/+0 www.nature.com/cgt