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From the first designed cell-penetrating transporters to carts: basic science and clinical applications

Prof. Paul Wender
Stanford University
Tuesday, 18 February 2020 12:00

Prof. Paul Wender

Department of Chemistry Department of Chemical and Systems Biology Stanford University. 

Stanford, CA 94305 USA 


Our research seeks to create function through nature-inspired, computer-assisted and synthesis-informed design directed principally at unsolved medical problems (Accounts 2008, 2013, 2015; NP Reports 2014). We start with such problems and use design to create potential chemical and biological solutions. These clinical challenges include the as yet unachieved goal of a cure for HIV/AIDS, universal flu vaccines, a strategy to treat MS, small molecule enhanced immuno-oncology, ex vivo and in vivo cell therapies, infection diseases (MRSA, VRE, etc), overcoming resistant cancer, rejuvenation research, mRNA directed immuno-oncology, neurological disorders including Alzheimer’s and other indications. In line with some interests of IMDEA, this lecture will mainly focus on drug delivery: basic science and clinical ramifications.

In 1997, my group was the first to determine that the ability of the HIV Tat protein, unlike most proteins, to cross biological barriers was a function of the number and spatial array of its guanidinium groups (Nature Medicine 2000, 1253; Proc. Natl. Acad. Sci. (PNAS) 2000, 13003). This led to the first designed cell- penetrating “molecular transporters” (MoTrs), a term we coined to avoid the structurally restrictive cell- penetrating “peptide” terminology of the time. Indeed, we and others have since designed totally non- peptidic, superior transporters based on guanidinium-rich peptoid, carbamate, dendrimeric, carbonate, ester and other backbones (reviewed in part in Accounts 2013, 2944). Over the past 23 years, we have shown that our molecular transporters can be used to carry into cells and animals a variety of cargos including small molecules (Nature Med. 2000), peptides (Chem & Bio. 2001), proteins (J. Invest. Derm. 2001), genes (Human Gene Therapy 2003), metals, imaging agents (PNAS 2001, 2007), siRNA (PNAS 2012), mRNA (PNAS 2017, 2018, 2018), pDNA (Biomacromol. 2018), CRISPR/Cas and LNAs. Efficient passage across a variety of barriers is observed (e.g. skin, ocular, lung, BBB, biofilm, buccal, algal, bacterial, etc). MoTrs have been used to overcome resistant cancer (PNAS 2008; Gyn. Onco. 2012) and with the Cegelski Group even to enhance by orders of magnitude the efficacy of certain antibiotics (J. Am. Chem. Soc. 2018, 161; ACS Chem Bio 2019). They can also be targeted in a way that complements monoclonal targeting (Bioconjugate 2006). Many of these technologies have been licensed from Stanford by various companies.

Our newest MoTrs are charge-altering releasable transporters (CARTs) developed in collaboration with the Waymouth and Levy Groups (PNAS 2017, 2018, 2018; J. Am. Chem. Soc. 2019). CARTs are novel polyanion transporters which like conventional polycationic transporters electrostatically complex their polyanionic cargo, but unlike the latter they undergo a dynamic conversion to neutral byproducts enabling polyanionic cargo release in cells and avoiding toxicity issues often found with persistent cations. CARTs are step-economically formed (1-2 steps), tunable, and non-immunogenic. They exhibit excellent uptake of, for example, mRNA into a variety of cell lines including difficult to transfect lymphocytes (PNAS 2018). They carry a variety of cargos sizes including multiple cargos. Amazingly by changes only in the CART structure, CARTs exhibit organ selectivity in vivo (e.g. >95% spleen, 70% lung, etc) without the use of mAbs or targeting ligands. This is new. CART delivered mRNA has been shown to protect or cure mice (PNAS 2018) and to clear metastatic disease in mouse models (Cancer Res. 2019).