Improving in vivo and Clinical Imaging with Activatable Cell-penetrating Peptides
Olson ES, Aguilera TA, Jiang T, Barder TE, Crisp JL, Scadeng M, Ellies LG, Nguyen QT, Tsien RY.
University of California San Diego, USA
Activatable cell penetrating peptides (ACPPs) are polycationic cell penetrating peptides (CPPs) whose cellular uptake is minimized by a polyanionic inhibitory domain and then restored upon proteolysis of the peptide linker connecting the polyanionic and polycationic domains. Local activity of proteases able to cut the linker causes amplified retention in tissues and uptake into cells. Tumor uptake of ACPPs is up to 4 fold higher with a matrix metalloproteinase substrate (PLGLAG) as the linker than with a negative control composed of D-amino acids. Conjugation of ACPPs to macromolecular carriers such as dendrimers prolongs pharmacokinetics and increases delivery of payload (Cy5 or Gd-DOTA or both in the same molecule) to tumor for far-red or MR imaging. The dual labeled probe with Cy5 and Gd-DOTA enables whole body MRI scanning followed by fluorescence-guided surgery. Such fluorescence guidance improves tumor-free survival in two animal models. Thrombin-cleavable ACPPs accumulate in atherosclerotic plaques and experimental stroke models, so vascular pathologies can also be imaged. The ability of ACPPs to deliver various cargoes with enzymatic amplification to protease-expressing tissues in vivo offers clinical potential.
A Chemical Approach to Cell Fate Control
Sheng Ding
The Scripps Research Institute, USA
Recent advances in stem cell biology may make possible new approaches for the treatment of a number of diseases. A better understanding of molecular mechanisms that control stem cell fate as well as an improved ability to manipulate them are required. Toward these goals, we have developed and implemented high throughput cell-based phenotypic screens of arrayed chemical and gene libraries to identify and further characterize small molecules and genes that can control stem cell fate in various systems. This talk will provide latest examples of discovery efforts in my lab that have advanced our ability and understanding toward controlling stem cell fate, including self-renewal, survival, differentiation and reprogramming of pluripotent stem cells.
Total Synthesis of Biologically Active Natural Products
K.C. NICOLAOU, Ph.D.
Department of Chemistry and The Skaggs Institute for Chemical Biology
The Scripps Research Institute
10550 N. Torrey Pines Road, La Jolla, CA 92037
and
The Department of Chemistry and Biochemistry
University of California, San Diego
9500 Gilman Drive, La Jolla, CA 92093
kcn@scripps.edu
Intelligent drug discovery from Nature has been in practice for millennia and has a glorious history in terms of medical breakthroughs.1-3 Aspirin®, penicillin and Taxol® are but three examples of such stories. Such natural products provide fertile platforms for discovery and development in the area of chemical synthesis, chemical biology and medicine. These opportunities continue to fascinate and deliver new science as new structures come under scrutiny by synthetic chemists. In this lecture, a number of total synthesis endeavors will be summarized with emphasis on mechanistically-based design of new cascade reactions and synthetic strategies and chemical biology studies.
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1. Nicolaou, K.C. & Montagnon, T. (2008). Molecules that Changed the World. Wiley-VCH.
2. Nicolaou, K.C. & Snyder, S. (2003). Classics in Total Synthesis II. Wiley-VCH.
3. Nicolaou, K.C. & Sorensen, E. (1996). Classics in Total Synthesis. Wiley-VCH.
A Novel Approach to Drug Discovery and Development for Osteoporosis and Other Bone Diseases
Hua Zhu (David) Ke, Desmond Padhi, Chris Paszty
Amgen Inc., Thousand Oaks, California, USA
Osteoporosis is a skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. The 2004 U.S. Surgeon General report highlighted the enormous burden of osteoporosis-related fractures. It is estimated that 10 million Americans > 50 yr of age have osteoporosis with approximately 1.5 million fragility fractures each year. Another 34 million Americans are at high risk for osteoporosis. Strategy for prevention and treatment of osteoporosis includes life style changes (nutrition, physical activity, and fall prevention), addressing secondary factors (such as diseases or drug) that cause osteoporosis, and pharmacologic intervention (agents that inhibit bone resorption and stimulate bone formation). Current available therapies include estrogen, selective estrogen receptor modulators, bisphosphonates, calcitonin, strontium ranelate and parathyroid hormones. These agents, while offering some clinical benefits have many limitations including safety and efficacy concerns. Currently there are new potential therapies in late stage clinical trials (cathepsin K inhibitor) or awaiting U.S. FDA approval (RANKL inhibitor) that may offer advantages over existing therapies. This presentation will review a novel approach, inhibition of sclerostin, as an anabolic (stimulation of bone formation) drug target for a potential novel osteoporosis therapy. Sclerostin, a protein secreted by osteocytes, is a negative regulator of osteoblast differentiation/function and acts as an inhibitor of bone formation. In humans, complete lack of the sclerostin, due to inactivating mutations in the SOST gene, causes sclerosteosis, a rare genetic disease characterized by increased bone mass and increased bone mineral density throughout the skeleton. Similar to the human condition, sclerostin knock-out mice demonstrate increased trabecular and cortical bone mineral density and bone strength by increased bone formation. To explore the therapeutic potential of sclerostin as a target for the anabolic treatment of diseases in which bone loss is a significant component, a sclerostin neutralizing monoclonal antibody (Scl-Ab) has been developed. In an ovariectomy (OVX)-induced bone loss rat model of osteoporosis, Scl-Ab increased bone formation, restored trabecular and cortical bone mass and bone strength at all skeletal sites. In mice and rat fracture healing models, administration of Scl-Ab significantly improved bone healing. In a phase 1 trial in postmenopausal women with osteopenia, a single administration resulted in increases in serum bone formation markers (s BSAP, osteocalcin, P1NP), and a dose-dependent decrease in a serum bone resorption marker (CTX1). These effects were associated with an increase in bone mineral density. Taken together, these data suggest that inhibition of sclerostin by monoclonal antibody may be an attractive strategy for treatment of osteoporosis and improving fracture healing.
Oral Delivery of Oligonucleotides in Man
Lloyd Tillman
ISIS Pharmaceuticals, USA
Oral absorption of hydrophilic macromolecules such as oligonucleotides is limited due to poor permeability across GI mucosa. Generally bioavailability is nil without the use of enhancers that are purported to transiently open epithelial tight-junctions increasing paracellular absorption. This presentation reviews formulation requirements necessary to develop one such enhancer, the fatty acid sodium caprate (C10), into an effective solid dosage formulation for oral delivery of oligonucleotides. The presentation will also give a brief overview into antisense oligonucleotide technology along with the recent progress made in this field.