Federico Medda

Novel Cambinol Analogs as Sirtuin Inhibitors: Synthesis, Biological Evaluation, and Rationalization of Activity

The tenovins and cambinol are two classes of sirtuin inhibitor that exhibit antitumor activity in preclinical models. This report describes modifications to the core structure of cambinol, in particular by incorporation of substituents at the N1-position, which lead to increased potency and modified selectivity. These improvements have been rationalized using molecular modeling techniques. The expected functional selectivity in cells was also observed for both a SIRT1 and a SIRT2 selective analog.

Gonadotropin-Releasing Hormone Receptor Levels and Cell Context Affect Tumor Cell Responses to Agonist In vitro and In vivo

Activation of gonadotropin-releasing hormone (GnRH) receptors inhibits proliferation of transformed cells derived from reproductive tissues and in transfected cell lines. Hence, GnRH receptors represent a therapeutic target for direct action of GnRH analogues on certain proliferating cells. However, more cell biological data are required to develop this particular application of GnRH analogues. Therefore, we compared the effects of GnRH receptor activation in transfected HEK293 cells (HEK293([SCL60])) with transfected human ovarian cancer cell lines SKOV3 and EFO21, human hepatoblastoma HepG2 cells, and rat neuroblastoma B35 cells. Marked differences in receptor levels, magnitude of inositol phosphate generation, and dynamics of inositol phosphate turnover occurred in the different cells. Activation of GnRH receptors, expressed at high or moderate levels, inhibited the growth of HEK293([SCL60]) and B35 cells, respectively. Western blotting detected markers of apoptosis [cleaved poly(ADP-ribose) polymerase, caspase-9] in HEK293([SCL60]) and B35 following treatment with 100 nmol/L d-Trp(6)-GnRH-I. Cell growth inhibition was partially or completely rescued with inhibitor Q-VD-OPh or Ro32-0432. Low levels of GnRH receptor expression in transfected SKOV3, EFO21, or HepG2 activated intracellular signaling but did not induce apoptosis or significantly affect cell proliferation. Tumor xenografts prepared from HEK293([SCL60]) regressed during treatment with d-Trp(6)-GnRH-I and growth of xenografts derived from transfected B35 was slowed. SKOV3 xenografts were not growth inhibited. Therefore, differences in levels of GnRH receptor and signaling differentially affect the apoptotic machinery within cell lines and contribute to the cell type-specific effects of GnRH on growth. Further studies should exploit the growth-inhibitory potential of GnRH receptor activation in abnormal cells in diseased human tissues.

N1-Benzyl substituted cambinol analogues as isozyme selective inhibitors of the sirtuin family of protein deacetylases

The human deacetylase SIRT2 is believed to promote neurodegeneration with recent studies demonstrating that a reduction in the activity of SIRT2 can rescue alpha synuclein toxicity in Parkinsons disease models. In contrast, a second member of the sirtuin family, SIRT1, is believed to play a neuroprotective role. This dichotomy places an additional challenge in the path of sirtuin inhibitor development as a need for isozyme selectivity arises. By combining computational methods with assessment of the biological activity of novel N1-substituted cambinol analogues, further insights that are relevant to this challenge are obtained.

Design and Synthesis of Fsp3-Rich, Bis-Spirocyclic-Based Compound Libraries for Biological Screening

The exploration of innovative chemical space is a critical step in the early phases of drug discovery. Bis-spirocyclic frameworks occur in natural products and other biologically relevant metabolites and show attractive features, such as molecular compactness, structural complexity, and three-dimensional character. A concise approach to the synthesis of bis-spirocyclic-based compound libraries starting from readily available commercial reagents and robust chemical transformations has been developed. A number of novel bis-spirocyclic scaffold examples, as implemented in the European Lead Factory project, is presented.

A Versatile Strategy for the Synthesis of 4,5-Dihydroxy-2,3-Pentanedione (DPD) and Related Compounds as Potential Modulators of Bacterial Quorum Sensing

Resistance to antibiotics is an increasingly serious threat to global public health and its management translates to significant health care costs. The validation of new Gram-negative antibacterial targets as sources for potential new antibiotics remains a challenge for all the scientists working in this field. The interference with bacterial Quorum Sensing (QS) mechanisms represents a potentially interesting approach to control bacterial growth and pursue the next generation of antimicrobials. In this context, our research is focused on the discovery of novel compounds structurally related to (S)-4,5-dihydroxy-2,3-pentanedione, commonly known as (S)-DPD, a small signaling molecule able to modulate bacterial QS in both Gram-negative and Gram-positive bacteria. In this study, a practical and versatile synthesis of racemic DPD is presented. Compared to previously reported syntheses, the proposed strategy is short and robust: it requires only one purification step and avoids the use of expensive or hazardous starting materials as well as the use of specific equipment. It is therefore well suited to the synthesis of derivatives for pharmaceutical research, as demonstrated by four series of novel DPD-related compounds described herein.

Abstract 2661: Novel albumin-binding maytansinoids inducing long-term partial and complete tumor regressions in several human cancer xenograft models in nude mice

MDA-MB 468 Maytansine and its analogs (e.g. DM1 and DM4) are potent microtubule-targeting compounds with a narrow therapeutic window. So far, only T-DM1, an antibody-maytansinoid conjugate targeting the HER2 receptor, has been approved for the treatment of Herceptin®-resistant breast cancer. Our design of two novel albumin-binding maytansinoids (LADR-9 and LADR-10) is based on: • Identification of two novel maytansine-based highly potent payloads (ANSA-05, ANSA-13), selected from screening a library of maytansinoids in vitro (Poster #1657) • Derivatization with a new water-solubilizing linker (SULF-07) resulting in LADR-9 and LADR-10 which bind in situ to the Cys-34 position of endogenous albumin • Accumulation of the drug-albumin conjugate in tumor tissue • Acid-mediated drug release at the tumor site INTRODUCTION & RATIONALE

Inhibitors to Overcome Secondary Mutations in the Stem Cell Factor Receptor KIT

In modern cancer therapy, the use of small organic molecules against receptor tyrosine kinases (RTKs) has been shown to be a valuable strategy. The association of cancer cells with dysregulated signaling pathways linked to RTKs represents a key element in targeted cancer therapies. The tyrosine kinase mast/stem cell growth factor receptor KIT is an example of a clinically relevant RTK. KIT is targeted for cancer therapy in gastrointestinal stromal tumors (GISTs) and chronic myelogenous leukemia (CML). However, acquired resistance mutations within the catalytic domain decrease the efficacy of this strategy and are the most common cause of failed therapy. Here, we present the structure-based design and synthesis of novel type II kinase inhibitors to overcome these mutations in KIT. Biochemical and cellular studies revealed promising molecules for the inhibition of mutated KIT.