AEZS-108 : a targeted cytotoxic analog of LHRH for the treatment of cancers positive for LHRH receptors.

INTRODUCTION

Receptors for the luteinizing hormone-releasing hormone [LHRH, also known as gonadotropin-releasing hormone (GnRH)] can be regarded as an ideal target for a personalized medicine approach in cancer therapy. LHRH receptors are expressed in about 80% of human endometrial and ovarian cancers, 86% of prostate cancer, and about 50% of breast cancers including triple-negative breast cancer, as well as bladder, colorectal, and pancreatic cancers, sarcomas, lymphomas, melanomas, and renal cell carcinomas. Apart from the pituitary and reproductive organs, other organs and hematopoietic stem cells express LHRH receptors. Thus, a targeted cytotoxic LHRH analog such as AEZS-108 (formerly known as AN-152), in which doxorubin is linked to the LHRH agonist [D-Lys(6)]LHRH, appears to be a suitable drug for targeted chemotherapy of cancers expressing receptors for LHRH, which would be more efficacious and less toxic than standard systemic chemotherapy.

AREAS COVERED

This review discusses the development of AEZS-108, its targeting mechanism, preclinical studies, and clinical trials in patients with endometrial, ovarian, prostatic, and bladder cancers. We emphasize its development as a personalized medicine approach. The studies reviewed demonstrate the effects of the cytotoxic LHRH analog, AEZS-108, mediated by LHRH receptors, in in vivo models of LHRH-receptor-positive human endometrial, ovarian, breast, prostatic, colorectal, pancreatic, and bladder cancers xenografted into nude mice. Intravenous administration of AEZS 108 inhibits the growth of LHRH-receptor-positive tumors better than equimolar doses of the cytotoxic agent doxorubicin and is far less toxic. AEZS 108 has no antitumor activity in cancers negative to LHRH receptor. This strongly supports the concept of targeting cytotoxic chemotherapy to tumor cells expressing LHRH receptors. Early clinical trials have demonstrated the efficacy of AEZS-108. A Phase I trial assessed the maximum tolerated dose and pharmacokinetics and pharmacodynamics of AEZS-108 given once every 3 weeks in patients with gynecological cancers. Two Phase II studies in heavily pretreated ovarian and recurrent endometrial cancers showed good clinical activity after a maximum of six courses of AEZS-108 as a single agent. Ongoing clinical studies with AEZS-108 in men with castration-resistant prostate cancer and patients with chemotherapy refractory bladder cancer had shown early signs of clinical efficacy. Side effects are moderate and easily manageable. In particular, no pituitary or cardiac toxicity is observed.

EXPERT OPINION

AEZS-108 is a cytotoxic analog designed for receptor-mediated targeted chemotherapy and consists of an LHRH carrier linked to doxorubicin. Preclinical studies demonstrate that the uptake of AEZS-108 is achieved by receptor-mediated endocytosis. Results of Phase I and II clinical trials in patients with gynecological cancers demonstrated anticancer activity without cardiotoxicity even in highly pretreated patients. Phase I/II studies in castration-resistant prostate cancer and chemotherapy refractory bladder cancer are in progress. Targeted chemotherapy with a cytotoxic analog of LHRH, such as AEZS-108, is therefore being considered for Phase III studies in advanced endometrial cancers positive for LHRH receptor. LHRH receptors are also present in human colon cancers, melanomas, lymphomas, and sarcomas, and treatment of these cancers with AEZS-108 should also be undertaken. Before such treatment with AEZS-108 is begun, the status of tumoral LHRH receptors of patients must be determined.