Use of Analogs of Peptide Hormones Conjugated to Cytotoxic Radicals for Chemotherapy Targeted to Receptors on Tumors

Andrew      V. Schally; Jorg      B. Engel; Gunter      Emons; Norman      L. Block; Jacek      Pinski

doi:10.2174/156720111793663598

Abstract

Specific receptors for luteinizing hormone-releasing hormone (LH-RH), somatostatin, bombesin, and other peptides are found on various cancers. We review the development of cytotoxic analogs of LH-RH, somatostatin, and bombesin/gastrin releasing peptide (GRP) designed for targeting chemotherapy to peptide receptors on various cancers. Cytotoxic analogs of LH-RH, AN-152 and AN-207, containing doxorubicin (DOX) or 2-pyrrolino-DOX (AN-201), respectively, target LH-RH receptors and may be used for the treatment of prostatic and urinary bladder (urothelial), breast, ovarian and endometrial cancers, non-Hodgkins lymphomas, melanomas, and renal cell carcinomas. DOX and AN-201 have also been incorporated into the cytotoxic analogs of somatostatin, AN-162 and AN-238, respectively, which are targeted to receptors for somatostatin in prostatic, mammary, ovarian, gastric, renal, colorectal and pancreatic cancers, non- Hodgkins lymphomas, as well as glioblastomas and lung cancers. They are found to suppress the growth of these tumors and their metastases. A cytotoxic analog of bombesin/GRP, AN-215, containing 2-pyrrolino-Dox, has also been synthesized and shown to inhibit growth of various human cancer lines expressing receptors for bombesin/GRP. The toxicity, pharmacokinetics and maximum tolerated doses of AN-152 were assessed in a phase I clinical trial in women with ovarian or endometrial cancer. Disease stabilization and objective responses were found. Analog AN-152 is now in phase II clinical trials. Phase I/II studies with AN-152 in men with hormone-independent relapsed prostate cancer and patients with pancreatic and bladder cancers are pending. Targeted cytotoxic peptide analogs could provide a more efficacious and less toxic therapy for various cancers.

Keywords: Targeted chemotherapy, targeted cytotoxic analogs of LH-RH, cytotoxic analogs of somatostatin, cytotoxic analogs of bombesin, tumor therapy, doxorubicin, Avastin, bevacizumab, vascular endothelial growth factor, radionuclides, indium, gallium, yttrium, Epithelial Ovarian Cancer, Endometrial Cancer, Urinary Bladder (Urothelial) Cancers, Renal Cell Carcinomas, Non-Hodgkin's Lymphomas, Decapeptyl, Colorectal Cancer, castration resistant prostate cancer, dose-limiting toxicity, circulating tumor cells, Prostate Cancer, Renal Cell Carcinoma (RCC), Glioblastomas, astrocytomas, Pancreatic Cancer, Colorectal Cancers, Gastric Cancers, Hepatocellular Carcinoma, Non-Hodgkin's Lymphoma, Bombesin, Gastrin Releasing Peptide