Phase I and pharmacokinetic study of Bay 38-3441, a camptothecin glycoconjugate, administered as a 30-minute infusion daily for five days every 3 weeks in patients with advanced solid malignancies

The Search for Anticancer Agents from Tropical Plants

Many of the clinically used anticancer agents in Western medicine are derived from secondary metabolites found in terrestrial microbes, marine organisms, and higher plants, with additional compounds of this type being currently in clinical trials. If plants are taken specifically, it is generally agreed that the prospects of encountering enhanced small organic-molecule chemical diversity are better if tropical rather than temperate species are investigated in drug discovery efforts. Plant collection in tropical source countries requires considerable preparation and organization to conduct in a responsible manner that abides by the provisions of the 1992 Rio Convention of Biological Diversity and the 2010 Nagoya Protocol on Access to Genetic Resources. Correct taxonomic identifications and enhanced procedures for processing and documenting plant samples when collected in often difficult terrain are required. Phytochemical aspects of the work involve solvent fractionation, known compound dereplication, preliminary in vitro testing, and prioritization, leading to "activity-guided fractionation", compound structure determination, and analog development. Further evaluation of lead compounds requires solubility, formulation, preliminary pharmacokinetics, and in vivo testing in suitable models. Covering the work of the authors carried out in two sequential multidisciplinary, multi-institutional research projects, examples of very promising compounds discovered from plants acquired from Africa, Southeast Asia, the Americas, and the Caribbean region, and with potential anticancer activity will be mentioned. These include plant secondary metabolites of the diphyllin lignan, cyclopenta[b]benzofuran, triterpenoid, and tropane alkaloid types.

The long story of camptothecin: From traditional medicine to drugs

20-(S)-Camptothecin (CPT) is a natural alkaloid extracted from the bark of Camptotheca acuminata (Chinese happy tree). It acts as a DNA topoisomerase 1 poison with an interesting antitumor activity and its use is limited by low stability and solubility and unpredictable drug-drug interactions. Since the late 20th century, it has been widely used in cancer therapy and, since extraction yields from plant tissues are very low, various synthetic routes have been developed to satisfy the increase in demand for CPT. Moreover, SAR studies have allowed for the development of more potent CPT analogues topotecan and irinotecan. Unfortunately, resistance has already occurred in several tumour lines. Additional studies are needed to better understand the relationship between substituents and resistance, its clinical relevance and the impact of related gene polymorphism. One of the latest research approaches focuses on modifying the delivery mode to improve tumour cell uptake and reduce toxicity.

The fate of camptothecin glycoconjugate: report of a clinical hold during a phase II study of BAY 56-3722 (formerly BAY 38-3441), in patients with recurrent or metastatic colorectal cancer resistant/refractory to irinotecan

Introduction BAY 56-3722 (formerly BAY 38-3441) is a glycoconjugated campthotecin, which was considered an attractive drug to assess in colorectal cancer (CRC). Patient and methods Phase II study design evaluating the antitumor activity of BAY 56-3722 IV 320 mg/m² daily for 3 days every 3 weeks in patients with recurrent or metastatic inoperable CRC resistant to irinotecan. Results Twenty-four patients received the study treatment. Triggered by adverse events in two other studies with this compound the study was put on a clinical hold while the safety data were reviewed for the entire program. After the review Bayer decided to withdraw BAY 56-3722 from all clinical investigations. Discussion We felt it was our obligation to share this interrupted phase II study for two reasons: to report the fate of camptothecin glycoconjugate and to report the unique situation of a clinical hold during a phase II study.