Efficacy of camptothecin analog DX-8951f (Exatecan Mesylate) on human pancreatic cancer in an orthotopic metastatic model.

We determined the antitumor and antimetastatic efficacy of the camptothecin analogue DX-8951f in an orthotopic metastatic mouse model of pancreatic cancer. DX-8951f showed efficacy against two human pancreatic tumor cell lines in this model. These cell lines were transduced with the green fluorescent protein, enabling high-resolution visualization of tumor and metastatic growth in vivo. The DX-8951f studies included both an early and advanced cancer model. In the early model, using the human pancreatic cancer lines MIA-PaCa-2 and BxPC-3, treatment began when the orthotopic primary tumor was approximately 7 mm in diameter. DX-8951f was significantly effective against both MIA-PaCa-2 and BxPC-3. In contrast, 2', 2'-difluorodeoxycytidine (gemcitabine), the standard treatment for pancreatic cancer, did not have significant efficacy against MIA-PaCa-2. Although gemcitabine showed significant activity against BxPC-3 primary tumor growth, it was not effective on metastasis. In the model of advanced disease, using BxPC-3, treatment started when the orthotopic primary tumor was 13 mm in diameter. DX-8951f was significantly effective in a dose-response manner on the BxPC-3 primary tumor. DX-8951f also demonstrated antimetastatic activity in the late-stage model, significantly reducing the incidence of lymph node metastasis while eliminating lung metastasis. In contrast, gemcitabine was only moderately effective against the primary tumor and ineffective against metastasis at both sites in the late-stage model. Therefore, DX-8951f was highly effective against primary and metastatic growth in this very difficult-to-treat disease and showed significantly higher efficacy than gemcitabine, the standard treatment of pancreatic cancer. DX-8951f, therefore, has important clinical promise and has more positive features than the currently used camptothecin analogue CPT-11, which requires metabolic activation and is toxic.