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Evidence for the efficacy of targeted alpha therapy for the control of pancreatic cancer in preclinical models is reviewed. Results are given for in vitro pancreatic cancer cells and clusters and micro-metastatic cancer lesions in vivo. Two complementary targeting vectors are examined. These are the C595 monoclonal antibody that targets the MUC1 antigen and the PAI2 ligand that targets the uPA receptor. The expression of the tumor-associated antigen MUC-1 and the uPA receptor on three pancreatic cancer cell lines is reported for cell clusters, human mouse xenografts and lymph node metastases, as well as for human pancreatic cancer tissues, using immuno-histochemistry, confocal microscopy and flow cytometry. The targeting vectors C595 and PAI2 were labeled with the alpha emitting radioisotope 213Bi using the chelators cDTPA and CHX-A″ to form the alpha-conjugates (AC). Cell clusters were incubated with the AC and examined at 48 hours. Apoptosis was documented using the TUNEL assay. In vivo, the anti-proliferative effect for tumors was tested at two days post-subcutaneous cell inoculation. Mice were injected with different concentrations of AC by local or systemic administration. Changes in tumor progression were assessed by tumor size. MUC-1 and uPA are strongly expressed on CFPAC-1, PANC-1 and moderate expression was found CAPAN-1 cell clusters and tumor xenografts. The ACs can target pancreatic cells and regress cell clusters (~100 µm diameter), causing apoptosis in some 70–90 % of cells. At two days post-cell inoculation in mice, a single local injection of 74 MBq/kg of AC causes complete inhibition of tumor growth. Systemic injections of 111, 222 and 333 MBq/kg of alpha-conjugate caused significant tumor growth delay in a dose dependent manner after 16 weeks, compared with the non-specific control at 333 MBq/kg. Cytotoxicity was assessed by the MTS and TUNEL assays. The C595 and PAI2-alpha conjugates are indicated for the treatment of micro-metastatic pancreatic cancer with over-expression of MUC1 and uPA receptors in post-surgical patients with minimal residual disease. The observation of tumor regression in a Phase I clinical trial of targeted alpha therapy for metastatic melanoma indicates that alpha therapy can regress tumors by a process called tumor anti-vascular alpha therapy (TAVAT). As a consequence, this therapy could be indicated for the management of non-surgical pancreatic cancer tumors.

The plasminogen activator inhibitor type 2 (PAI2) when labelled with (213)Bi forms the (213)Bi-PAI2 alpha conjugate (AC). This AC has been shown to be efficacious in preclinical studies with breast, ovarian, prostate and pancreatic cancers. The objectives of this study were to investigate the pharmacokinetics and in vivo stability of (213)Bi-PAI2 in mice, its toxicity in mice and rabbits; and to determine whether a prior injection of a metal chelator (Ca-DTPA) or lysine can reduce toxicity by decreasing renal uptake.Two chelators (CHX-A"-DTPA and cDTPA) were used for preparation of the (213)Bi-PAI2 conjugate, for intraperitoneal administration in mice and ear vein injection in rabbits. The mice were sacrificed at different time points for pharmacokinetic studies. Blood and organs were collected for toxicity studies for all groups.Both chelators were found to have similar %ID/g in the kidneys over four hours. Mice and rabbits did not show any short term toxicity over 13 weeks at 1420 MBq/kg and 120 MBq/kg (213)Bi-PAI2 respectively. Kidney uptake was decreased three fold by lysine. Radiation nephropathy was observed at 20-30 weeks in mice, leading to severe weight loss, whereas severe and widespread renal tubular necrosis was observed at 13 weeks in rabbits.Radiation nephropathy is the dose limiting toxicity observed in mice and rabbits. Lysine can reduce kidney uptake by three fold. Based on long-term monitoring, the maximum tolerance doses (MTD) are 350 and 120 MBq/kg for mice and rabbits respectively.

Control of ovarian cancer (OC) ascites remains a major objective in post-surgical treatment. The aim of this study was to investigate the effect of targeted alpha therapy (TAT) for the control of ascites in an OC ascites mouse model; the biodistribution of (213)Bi-C595 and its long term toxicity.The expression of tumor-associated antigen mucin-1 (MUC-1) in OVCAR3 ascites cells in mice and OC cancer tissues in patients was detected by indirect immmunostaining. The monoclonal antibody (MAb) C595 was labeled with (213)Bi using the chelator cDTPA to form the alpha-immunoconjugate (AIC). Mice were injected with different concentrations of AIC by i.p administration. Changes in tumor progression were assessed by measurement of the circumference of the abdomen.MUC-1 is strongly expressed in 73% of OC tissues. At 9 days post-cell inoculation in mice, a single injection of 355 MBq/kg of (213)Bi-C595 can prolong survival by 25 days. A high tumor: blood ratio (5.8) was found in biodistribution study. The maximum tolerance dose (MTD) was more than 1180 MBq/kg up to 21 weeks.C595 is a specific targeting vector for ovarian cancer cells, which show a high percentage of expression of MUC1. (213)Bi-C595 can effectively target and kill ovarian cancer cells in vitro and in vivo. (213)Bi-C595 is the recommended alpha conjugate for a Phase I clinical trial for ovarian cancer.

The aim of this study was to investigate the effect of targeted alpha therapy for the control of in vitro pancreatic cancer cell clusters and micrometastatic cancer lesions in vivo.The expression of tumor-associated antigen MUC-1 on three pancreatic cancer cell clusters and animal xenografts was detected by indirect immmunostaining. Monoclonal antibodies C595 (test) and A2 (non-specific control) were labeled with 213Bi using the chelator CHX.A" to form the alpha-immunoconjugate (AIC). Cell clusters were incubated with AIC and examined at 48 h. Apoptosis was documented using the TUNEL assay. In vivo, an antiproliferative effect for tumors was tested at two days post-subcutaneous cell inoculation. Mice were injected with different concentrations of AIC by regional or systemic administration. Changes in tumor progression were assessed by tumor size.MUC-1 is strongly expressed on CFPAC-1, PANC-1 and moderate expression was found CAPAN-1 cell clusters and tumor xenografts. The AICs can target and kill cancer cell clusters (100 mm) in vitro. Some 73-81 % of cells were TUNEL positive cells in the clusters after incubation with AIC. At two days post- cell inoculation in mice, a single local injection of 74 and 148 MBq/kg of AIC causes complete inhibition of tumor growth. Systemic injections of 111, 222 and 333 MBq/kg of AIC cause significant tumor growth delay after 16 weeks, compared with the nonspecific control providing 333 MBq/kg after 16 weeks.CFPAC-1, PANC-1 and CAPAN-1 pancreatic cancer cell clusters and pancreatic tumor xenografts show high expression of the MUC-1 target antigen. 213Bi-C595 can specifically target and regress pancreatic cancer cell clusters in vitro, and delay and inhibit tumor growth in vivo. 213Bi-C595 may be a useful agent for the treatment of micrometastatic pancreatic cancer with overexpression of MUC 1 antigen in post-surgical patients with minimal residual disease.

Background: Monoclonal antibodies (MAbs) can be used to detect, image and treat cancers. This study aimed to characterise the binding of BLCA-38 MAbs to human prostate cancer cell lines, human prostate cancer biopsy samples and normal tissues to enable future targeted studies. Methods: BLCA-38 antigen expression on cancer lines was determined by flow cytometry; that on patient specimens from normal tissues and cancers was tested by immunohistochemistry using fresh frozen tissues or paraffin-embedded tissues that had undergone antigen retrieval. Results: Cell surface BLCA-38 antigen expression was seen on DU-145, PC-3, PC-3 M and PC-3 M-MM2 prostate cancer lines, but LNCaP, MDA PCa 2a or MDA PCa 2b lines were negative. Other human lines, including 8/12 bladder cancer and A431 vulval epidermoid cells, but not breast cancer lines, expressed BLCA-38 antigen. Staining occurred in glandular epithelial cells in the majority of frozen, and paraffin-embedded prostate cancer tissues and was occasionally seen in prostatic intraepithelial neoplasia (PIN). No staining was observed in normal cadaver tissues or in benign areas from various other cancer tissues. Conclusions: The BLCA-38 antibody binds to the majority of human prostate cancers but not to normal cells, and has potential for targeting novel therapies in patients with this disease.