Targeted Rx for pancreatic cancer

HOUSTON—An experimental gene therapy targeting pancreatic cancer reduced or eradicated tumors, inhibited metastasis, and prolonged survival in experiments in two mouse models, and did so with very limited toxicity. Researchers at M.D. Anderson Cancer Center are compiling additional preclinical data for FDA review and hope to begin a phase I trial of the therapy in 1 to 2 years.

"This vehicle, or vector, is so targeted and robust in its cancer-specific expression that it can be used for therapy and perhaps for imaging," said senior author Mien-Chie Hung, PhD, professor and chair of the Department of Molecular and Cellular Oncology. He and his colleagues reported their preclinical findings in Cancer Cell (12:52-65, 2007).

"There are no good options for pancreatic cancer patients now," said James Abbruzzese, MD, professor and chair of M.D. Anderson's Department of Gastrointestinal Oncology, who with other clinicians is now working with Dr. Hung to bring the therapy to clinical trials. "This looks like a promising approach to gene therapy for pancreatic cancer."

Dr. Hung and his team call the system a versatile expression vector and nicknamed it VISA. The molecularly engineered therapy specifically embeds a mutated, more lethal version of the Bik gene—which expresses a protein that signals cancer cells to destroy themselves—into pancreatic cells.

The system consists of a targeting molecule, or promoter; two components that enhance gene expression in the target tissue; and the mutated gene, which the researchers have designated BikDD. These components are packaged in liposomes and delivered intravenously.

M.D. Anderson has licensed the technology to Alchemgen Therapeutics Inc., a Houston-based company cofounded by Dr. Hung.

In the preclinical studies, the researchers tested VISA against two aggressive pancreatic cancer lines in two different mouse models.

All of the untreated control animals died within 40 days in the experiments. Among mice treated with BikDD that was delivered with a system using cytomegalovirus (CMV), a lesser targeting agent, all the animals died within 90 days, and most of them much sooner. In both trials, however, the mice treated with VISA-BikDD had a significantly longer survival, and at least half lived for 14 months without a detectable recurrence of pancreatic cancer.

No detectable metastases

In a test of a rapidly spreading pancreatic cancer cell line, live imaging demonstrated that the cancer metastasized in control mice to the liver, spleen, kidneys, bladder, lungs, bone, and intestines. The CMV-BikDD-treated animals showed only a small number of tumors in nearby organs, and mice that received VISA-BikDD had no detectable metastases.

The toxicity findings from the studies proved equally encouraging, Dr. Hung and his colleagues reported. They looked for acute systemic toxicity and pancreatitis and found that the CMV-BikDD- treated mice showed indications of both. However, "VISA-BikDD produces virtually no systemically acute toxicity or acute pancreatitis," Dr. Hung said.

His group continues to explore the VISA concept in other malignancies. "VISA is versatile enough that if you change the promoter, you could target other cancers or even other diseases," Dr. Hung said.