A comprehensive view on mechanistic approaches for cancer risk assessment of non-genotoxic agrochemicals.

Currently the only methods for non-genotoxic carcinogenic hazard assessment accepted by most regulatory authorities are lifetime carcinogenicity studies. However, these involve the use of large numbers of animals and the relevance of their predictive power and results has been scientifically challenged. With increased availability of innovative test methods and enhanced understanding of carcinogenic processes, it is believed that tumour formation can now be better predicted using mechanistic information. A workshop organised by the European Partnership on Alternative Approaches to Animal Testing brought together experts to discuss an alternative, mechanism-based approach for cancer risk assessment of agrochemicals. Data from a toolbox of test methods for detecting modes of action (MOAs) underlying non-genotoxic carcinogenicity are combined with information from subchronic toxicity studies in a weight-of-evidence approach to identify carcinogenic potential of a test substance. The workshop included interactive sessions to discuss the approach using case studies. These showed that fine-tuning is needed, to build confidence in the proposed approach, to ensure scientific correctness, and to address different regulatory needs. This novel approach was considered realistic, and its regulatory acceptance and implementation can be facilitated in the coming years through continued dialogue between all stakeholders and building confidence in alternative approaches.

Is sunitinib a Narrow Therapeutic Index Drug? - A systematic review and in vitro toxicology-analysis of Sunitinib vs. Imatinib in cells from different tissues.

Narrow Therapeutic Index Drugs (NTIDs) are characterized by a small range between therapeutic and toxicological effect. Missing international harmonized definition for NTIDs the EMA does not even have a definition of NTIDs in contrast to the U.S. FDA, Health Canada, and the Japanese NIHS. Sunitinib, a tyrosine kinase inhibitor (TKI), indicated for the treatment of certain cancer types, will be running off-patent soon. Falling into the category of NTID would have a major impact on regulatory requirements for generic applications. Our analyses of metadata revealed numerous arguments in favor of a NTID designation. We used in vitro experiments to also give initial experimental answers. Five cell types of different tissue origin were examined for determination of IC50-values in cell viability assays. For comparison, the first-in-class TKI Imatinib was used as reference non-NTID drug. In addition, apoptotic proteins were investigated with respect to their expression and phosphorylation status. These in vitro experiments showed systematically higher toxicity of Sunitinib compared to Imatinib and a different expression and phosphorylation pattern of apoptotic proteins. In vitro data can only give preliminary results and further experiments with clinical blood samples and tumor biopsies are needed to finally clarify NTID status of Sunitinib.

Clinical pharmacology and regulatory consequences of GnRH analogues in prostate cancer.

INTRODUCTION: GnRH (gonadotropin-releasing hormone) analogues are long-term known to be safe and effective in the clinical management of hormone-dependent advanced prostate cancer. However, their unusual mechanism of action of de-sensitizing pituitary receptors makes generic market entry challenging. In addition, safety aspects like initial flare-up, breakthrough escape, and miniflares render planning and organization of clinical registration trials a complex project. REGULATORY REQUIREMENTS THERAPEUTIC EQUIVALENCE: Regulatory requirements are high as these medicines are compared to bilateral surgical castration with a 100% success rate. GnRH analogues will be used probably even wider in the near future due to demographic development and extension of indications. However, they are challenged by their antagonistic counterparts, which are avoiding flare-up phenomena. The following article deals with regulatory requirements of GnRH analogues in regard to their clinical characteristics.

Clinical pharmacology of tyrosine kinase inhibitors becoming generic drugs: the regulatory perspective.

Over the last decades, billions have been spent and huge efforts have been taken in basic and clinical cancer research [CA Cancer J Clin63:11-30]. About a decade ago, the arms race between drugs and cancer cells reached a new level by introduction of tyrosine kinase inhibitors (TKI) into pharmacological anti-cancer therapy. According to their molecular mechanism of action, TKI in contrast to so-called "classic" or "conventional" cytostatics belong to the group of targeted cancer medicines, characterized by accurately fitting with biological structures (i.e. active centers of kinases). Numerous (partly orphan) indications are covered by this new class of substances. Approximately ten years after the first substances of this class of medicines were authorized, patent protection will end within the next years. The following article covers clinical meaning and regulatory status of anti-cancer TKI and gives an outlook to what is expected from the introduction of generic anti-cancer TKI.