Recent Publications

KJEMS, JORGEN, Ferapontova, Elena, Gothelf, Kurt V. (Eds.)

Nucleic Acid Nanotechnology

Nucleic Acids and Molecular Biology, Vol. 29Direct link
Prusty,B.K., Karlas,A, Meyer,T.F., and Rudel,T. (2011).

Genome-wide RNAi screen for viral replication in mammalian cell culture

Methods Mol. Biol. 271, 383-395Direct link

Research areas

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The ANTIFLU project builds upon two main therapeutic approaches, small molecule inhibitors and RNAi based inhibitors, both targeting human factors.

The scientific approach of ANTIFLU follows the conventional systematic drug discovery process including the steps of target identification and validation, hit identification, hit-to-lead development and lead optimisation, preclinical testing, GLP/GMP up-scaling, and clinical phase I and II testing. By focussing on human targets for the development of drugs against influenza, we have the prospect of developing, for the first time, antiviral drugs that (i) do not trigger the development of viral resistance and (ii) are likely to defend humans from a variety of influenza strains. Human candidate targets have been successfully identified in the process of a genome-wide RNAi screen for human factors essential for influenza virus replication in vitro (Karlas A, Machuy N. et al., Nature 2010, 463:818-22). ANTIFLU will follow two independent strategies to attack the most promising human targets: The first strategy is based on posttranslational binding and inactivation of the corresponding human gene products (proteins) by small molecules or new chemical entities. The second approach focuses on RNAi-based posttranscriptional prevention of expression of the respective human genes. Both strategies follow the same development scheme; the approaches are complementary in that siRNAs are suitable for ‘non-druggable’ targets, i.e. those considered inaccessible to small molecules. As an extension of these EU funded studies, the consortium has secured tentative financial commitment by private investor and big pharma to support further development and clinical testing of selected small molecule compounds and siRNAs, respectively, up to phase II clinical trials.

ANTIFLU project workflow


Small molecule inhibitors

Small molecule antiviral drugs already play a major part in the control of influenza infection. There are currently two classes of antivirals approved for use against influenza A viruses, the M2 inhibitors - amantadine and rimantadine and the neuraminidase inhibitors - Zanamivir and Oseltamivir. A major problem in influenza therapy results from the increase in resistances to M2 inhibitors and neuraminidase inhibitors. Thus, it becomes obvious that novel small molecule based drugs directed against human influenza targets with a broad applicability are urgently needed. One major focus of the ANTIFLU project therefore will be the discovery and further development of specific small molecule ligands acting on host cell targets. Provided that the intrinsic activity of a host cell protein also mediates an essential function for virus replication, small molecule based modulation of such a target might lead to antagonistic effects for virus propagation. They will present a valuable treatment option for infected influenza patients and even might be useful for prophylaxis. In case of the seasonal strain variations, such a drug could be readily used without the necessity for detailed diagnosis before drug treatment begins. The key during the development of a novel indirect anti-influenza drug will be to focus on safety in order to avoid target-mediated toxicities, using highest industrial standards and hard milestone criteria. This approach presents the answer to recently emerging needs in anti-influenza strategies, since it avoids the well known pitfalls of resistance formation and nevertheless is going to be broadly applicable. Therefore, it might be used for seasonal influenza, for avian and swine influenza, for a potential influenza pandemic as well as for stockpiling.

Early drug discovery

Early drug discovery

RNAi based inhibitors

RNA-mediated knockdown of protein expression at the messenger RNA (mRNA) level using siRNA offers a modern therapeutic strategy to overcome influenza. Studies in cell lines, embryonated chicken eggs as well as preclinical studies in mice have successfully been aimed at targeting influenza’s conserved regions such as the nucleocapsid protein or the polymerase. Our approach of RNA-mediated host gene targeting allows addressing any host cell factor, including the so far non-drugable ones and thereby significantly expands the array of possible therapeutic compounds and strategies beyond the scope ofsmall molecules and chemical entities which dominate the anti-influenza drug market so far. RNAi based antiviral therapy can reach a higher level of specificity either as a drug on its own or to support conventional small molecule inhibitors. Kinases for instance are amongst the most promising new targets but conventional kinase inhibitors frequently face the problem of being not specific to a single kinase but instead often affect a whole group of structurally related molecules. The specificity of siRNAs therefore presents an important advantage. With respect to the biological activity of our siRNA compounds we will amalgamate state of the art including unpublished features in order to (i) achieve maximum on-target activity, (ii) avoid off-target effects, (iii) suppress the immunostimulatory potential, and (iv) circumvent a competition of the siRNA with endogenous miRNAs for essential cellular factors. The effectiveness of anti-influenza RNAi drugs is heavily determined by their ability to localise within infected epithelial cells of the upper respiratory tract and lungs. Delivery across the mucous layer and avoidance of cilia clearance, however, is the challenge to RNAi-based influenza therapeutics. In addition, the polyanionic nature of siRNA reduces interaction with cellular membranes restricts uptake of naked siRNA into cells. Cationic polymer (polyplexes) and encapsulated polymeric nanoparticles are strategies to improve the therapeutic potential of siRNA by overcoming the extracellular and intracellular barriers to nucleic acid delivery.

RNAi Interference Technology

Optimisation of small interfering RNAs

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