Marine-derived anticancer agents in clinical trials

DNA and the chromosome - varied targets for chemotherapy

The nucleus of the cell serves to maintain, regulate, and replicate the critical genetic information encoded by the genome. Genomic DNA is highly associated with proteins that enable simple nuclear structures such as nucleosomes to form higher-order organisation such as chromatin fibres. The temporal association of regulatory proteins with DNA creates a dynamic environment capable of quickly responding to cellular requirements and distress. The response is often mediated through alterations in the chromatin structure, resulting in changed accessibility of specific DNA sequences that are then recognized by specific proteins. Anti-cancer drugs that target cellular DNA have been used clinically for over four decades, but it is only recently that nuclease specific drugs have been developed to not only target the DNA but also other components of the nuclear structure and its regulation. In this review, we discuss some of the new drugs aimed at primary DNA sequences, DNA secondary structures, and associated proteins, keeping in mind that these agents are not only important from a clinical perspective but also as tools for understanding the nuclear environment in normal and cancer cells.

Progress in the clinical development of new marine-derived anticancer compounds

Naturally derived anticancer agents continue to be instrumental in the systemic therapeutic intervention against solid tumors and hematological malignancies. Such compounds now have a relevant role in contemporary models of combination with targeted agents, thus providing a rationale to consider nature as a valid tool to discover new innovative anticancer agents. The marine ecosystem has increasingly been the focus of interest for new discoveries in the field that are expected to be of significant therapeutic impact in cancer patients. A critical review of the integrated data generated in our marine-derived anticancer program seems to confirm such expentancies. ET-743 (Yondelis) represents the first new agent developed against advanced pretreated soft tissue sarcoma in the past 25 years, and also harbors activity in women bearing pretreated ovarian cancer and a solid potential in combination therapy. The lack of cumulative toxicities makes this compound suitable for long-lasting therapies, reversible transaminitis being the most prevalent toxicity. Aplidin has shown a positive therapeutic index in phase I trials and phase II studies are ongoing. In contrast to the lack of bone marrow toxicity, a set of translational results anticipates a potential in leukemia. Kahalalide F has also successfully completed the phase I program in solid tumors with evidence of activity in resistant tumors and phase II studies are under way. Finally, the mechanistic data generated in parallel with the clinical program confirms the potential of the marine ecosystem in the discovery of new agents acting against new cellular targets of relevance in cancer cell biology.

Novel Marine Compounds: Anticancer or Genotoxic?

In the past several decades, marine organisms have generously gifted to the pharmaceutical industries numerous naturally bioactive compounds with antiviral, antibacterial, antimalarial, anti-inflammatory, antioxidant, and anticancer potentials. But till date only few anticancer drugs (cytarabine, vidarabine) have been commercially developed from marine compounds while several others are currently in different clinical trials. Majority of these compounds were tested in the tumor xenograft models, however, lack of anticancer potential data in the chemical- and/or oncogene-induced pre-initiation animal carcinogenesis models might have cost some of the marine anticancer compounds an early exit from the clinical trials. This review critically discusses importance of preclinical evaluation, failure of human clinical trials with certain potential anticancer agents, the screening tests used, and choice of biomarkers.