In vitro resistance to TMC207/R207910

Wednesday, December 30th, 2009 by hinrich

Structure of TMC207/R207910

In the article "Rates and mechanisms of resistance development in Mycobacterium tuberculosis to a novel diarylquinoline ATP synthase inhibitor" Huitric et al. looked at almost 100 different bacterial mutants that the authors identified from clinical isolates. They tried to establish how quickly M. tuberculosis can develop mutations in vitro that will confer resistance to the new investigational drug TMC207/R207910. Furthermore, Huitric et al. were interested in studying the mutants in more detail to learn about the mechanisms by which the bacterium can escape the bactericidal effect of TMC207/R207910.

When looking at the level of resistance, the authors determined a 4- to 128-fold increase in MIC (Minimum Inhibitory Concentration). Increasing the concentration of TMC207/R207910 resulted in a decrease of the rate at which high-level resistence occurred. How does this in vitro result translate to the clinical context? If the therapeutic dose in patients could be equal to or higher than the concentration at which such mutations do not occur while still avoiding toxicity, the positive effects of TMC207/R207910 might be even higher as clinical resistance would be less frequent.

Huitric et al. also studied the sequence of one or more of the genes that encode the bacterial ATP synthase in approximately half of the mutants. The authors identified mutations that would result in five different amino acid substitutions in the atpE gene. This gene had previously been identified and linked to the novel mechanism of action of TMC207/R207910. However, for 38 of the mutants no further mutations in the ATP synthase related genes were identified. This suggests that Mycobacterium tuberculosis has different mechanisms by which the bacterium can escape the effects of TMC207/R207910.

A review of the mechanism of action of TMC207/R207910 can be found in this Science Enhanced Perspectives article (free access). The article by Huitric et al. has just been published in Antimicrobial Agents and Chemotherapy. Please have a look here for further information.

Posted in Tuberculosis


Third generation sequencing for RNA profiling

Thursday, December 17th, 2009 by hinrich

Next-gen sequencing

All next-gen sequencing platforms (actually the 2nd generation systems) cannot directly sequence RNA (also referred to as "RNA seq"). They need to first convert the RNA into cDNA which in turn can be sequenced. While the different sequencing technologies themselves are very accurate and reproducible in generating the sequence reads, the enzymatic conversion step during the generation of the sequencing library can introduce errors or sequence biases.

On the other hand, third generation sequencing technologies (e.g., Helicos BioSciences or Pacific Biosiences) offer the potential to circumvent this step as they sequence the molecule directly. However, only one platform is already commercially available and it will be a challenge to adjust all parameters (e.g., buffers, reagents, RNase-free environment) for each platform to ensure that the sequence data will be of high quality and of sufficient read length.

Even though the providers of next-gen sequencing and a number of scientists push the public perception of using next-gen sequencing instead of microarrays for transcriptome analysis (see for example the Wikipedia article on RNA seq), routine transcriptome analysis is still predominantly carried out via microarray technology. However, focusing on enabling reproducible high quality RNA sequencing on a third generation platform early on could result in a significant market opportunity and a clear competitive advantage over microarrays.

Posted in Molecular Profiling


NGI Venture Challenge Fall 2009

Friday, December 04th, 2009 by hinrich

Over the last couple of weeks I have had the opportunity to participate in the NGI Venture Challenge which is organized by the Netherlands Genomics Initiative (NGI). The aim of this initiative is to educate people with an idea of commercial potential in the life sciences on how to write a venture plan and "turn a promising idea into a sound business case".

Attending two 3-day workshops and a number of individual coaching sessions we learned a lot about looking at our scientific findings in the field of human lung regeneration from a business point of view. Today we had to give our pitch in front of a jury in Utrecht. Even though we did not win the price of 25,000 Euro the new insights we gained and the new contacts we made are invaluable.

Thanks very much to the coaches and the Netherlands Genomics Initiative!

Posted in Science


Optimal IT support for research

Wednesday, December 02th, 2009 by hinrich

I have written about this before: research depends increasingly on IT. Both the IT infrastructure as well as appropriate software (predominantly written by rapid prototyping for cutting edge science) need to be provided in a proactive way to anticipate the trends in current molecular biology (e.g., microarrays, next-gen sequencing, high content screening). The question is how to approach IT support for research optimally?

Here are some elements I consider to be crucial:

Posted in Science


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