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International workshop on drug-drug interactions with high acceptance and great benefit

More than 60 experts from 11 countries and 5 participants at the industry exhibition joined the meeting on DDIs at Marbach Castle, Lake Constance in Germany. New methods and approaches for the investigation of drug candidates have become necessary due to the increasing complexity of this scientific area. Changes in the existing guideline on drug interactions must follow. Recently the European Medicines Agency (EMA) published a draft of the revised guideline, which was discussed in several talks at the DDI Workshop. In the US a new version of the existing FDA drug interaction guideline is under discussion but not published yet. Discussion of the current scientific status between representatives of the industry, regulatory bodies, and academia are of great importance and were successfully realized at the DDI Workshop.

More than 60 experts for drug development participated in the international DDI Workshop at Marbach Castle. © Simon Hermann/Steffen Reuter

More than 60 experts for drug development participated in the international DDI Workshop at Marbach Castle. Over a period of two days they listened to 14 expert presentations and discussed intensively the latest scientific and regulatory trends in the investigation of DDIs. Most of the participants were experts from the pharmaceutical industry. Almost all big companies were represented at the workshop. It was a big advantage that speakers and participants from regulatory bodies as well as academic institutions were also present generating useful and inspiring discussions and interdisciplinary exchange. Besides the scientific aspects the discussion focused on regulatory requirements of the investigation of DDIs.


What a lucky coincidence that EMA published the new draft of the guidelines exactly before the workshop started. Dr. Eva Gil Berglund from the Medical Product Agency (MPA) of Sweden, who is significantly involved in the preparation of the new guideline, had already agreed to speak at the workshop. Her speech together with the presentation of Professor Hartmut Derendorf showed that significant changes in the present draft of the guideline compared to the thirteen year old predecessor version will be implemented. New aspects like transporter-based DDIs will be included as well as interactions with food and OTC drugs, especially herbal drugs. Due to this additional sections within the European guideline there will be some differences between the respective US and European Guidance documents. However also various important commonalities are existing in terms of an international harmonization. Additionally the FDA is also planning to revise the existing guideline, which was published in 2006.

Some industry representatives asked during the workshop for additional and sometimes more detailed guidance on how in vitro and in vivo studies should be conducted by pharmaceutical companies in the future to qualify their products for marketing approval in Europe. As always in the finalisation process of such guidance documents, the draft version of the guideline will be subject to expert comments from industry and academia and therefore most likely pass through several changes. Dr. Eva Berglund was very open for comments and asked the audience repeatedly for written feedback. Experts should send their comments to the EMA or place the comment directly on the EMA website. The new draft is open for discussion until the end of October this year. The final version of the guideline can be expected by end of 2011.

The increasing importance of DDIs was highlighted in almost all speeches. Dr. Robert Hermann showed in his introduction that demographic changes in the industrial nations will cause an exponential increase of poly-pharmacotherapy. Approximately 60 percent of older adults (elder than 65 years) take at least 5 or more drugs and/or supplements at the same time. The cost for the treatment of adverse drug reactions or drug interactions has, in the meantime, reached the level of the total costs for pharmacotherapy itself. The current challenge for industry, regulatory agencies and the society is to gather more scientific data on drug interactions, to be more efficient in the development process of drug candidates, and to transform the available knowlegde into useful information for physicians and patients. The existing expert systems, which should support physicians and pharmacists, are not yet sufficient.

More efficient development of drugs as a challange

The organisation team and referents of the workshop (from left): Professor Uwe Fuhr (Universität Köln), Professor Andrew Parkinson (Lenaxa, USA), Dr. Oliver von Richter (Merck Serono), Professor Isabelle Ragueneau-Majlessi (Universität Washington, USA), Professor Hartmut Derendorf (Universität Florida, USA), Professor Amin Rostami-Hodjegan (Universität Manchester, UK) und Dr. Robert Hermann (cr.appliance) © Simon Hermann/Steffen Reuter

The experts agreed that a total coverage of all possible drug interaction with clinical trials is impossible. Transporter-based DDIs (tDDIs), a main topic of the workshop, are good examples for the increasing complexity. The withdrawal of the cholesterol lowering drug cerivastatin from the market in 2002 due to fatal interactions with gemfibrozil marked a turning point and demonstrated the importance of tDDIs. In the meantime the knowledge in tDDIs has grown significantly and Dr. Oliver von Richter presented the current status. Currently 8 of 1100 so far identified human transporter proteins are known to be involved in active drug transport and hence, may play a role in drug interactions. At present robust methods and specific tool substances to study tDDIs in vivo in humans are limited. It is all the more important that in vitro methods are available to identify transporter substrates and inhibitors.

The talk of Professor Uwe Fuhr covered so-called cocktail drug interaction studies (simultaneous investigation of several drugs in one study), which can help to gain a first overview and to reduce the number of studies for the assessment of the drug interaction potential of a drug candidate. Despite the well-known and addressed limitations, cocktail studies have achieved acceptance by regulatory agencies.
In addition to clinical in vivo studies, which produce the most reliable results, a broad spectrum of in vitro test systems like isolated recombinant enzyme systems, human microsomes or liver cells (hepatozytes) is available. The use of in vitro systems has recently become more popular and sophisticated due to the known limitations of predicting metabolism based DDIs (mDDIs) in humans based on animal data.

Professor Amin Rostami-Hodjegan gave a state-of-the-art lecture about mDDIs and presented the characteristics of the different in vitro systems. Professor Andrew Parkinson demonstrated very impressively that different in vitro test systems can also deliver controversial data. In principal only the observance of the complete data set allows a solid assessment of the results. Inconsistant data from in vitro tests will have to be rechecked in clinical trials.

About the DDI Workshop

The DDI Workshop is an initiative of cr.appliance in cooperation with Hartmut Derendorf, Amin Rostami-Hodjegan, and Oliver von Richter. The meeting was held in Marbach Castle Conference Centre, located at the Lake Constance, Germany.

Contact and Informations:
Karen Grave-Hermann
Mail: karen.grave-hermann(at)cr-appliance.com
Phone: +49 (0)7732 820 951 Fax: +49 (0)7732 820 953

Website address: https://www.gesundheitsindustrie-bw.de/en/article/press-release/international-workshop-on-drug-drug-interactions-with-high-acceptance-and-great-benefit