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Growing Interest in Outsourcing ION CHANNEL Services Ion channels:Layout 1 1/7/08 09:31 Page 33 Ion Channels growing interest in outsourcing ION CHANNEL services Significant demand now exists in Pharma and Biotech to access ion channel testing services and this is reflected by the number and the variety of service offerings. The majority of GLP cardiac safety hERG testing is outsourced today using manual patch clamping. Automated patch clamping (APC) systems are, however, undertaking an ever increasing role in the services offered and there appears to be increasing acceptance of their use as alternatives to the ‘gold standard’ manual patch clamp. This reflects recent improvements in quality of data generated with APC systems and the significant wealth of experience gained in their use. In the highly competitive area of cardiac safety hERG testing price and turn-around time are now key factors in the selection of a fee-for-service provider. CROs are also competing to offer new services and some are assembling large ion channel libraries, variously grouped into panels for use in selectivity profiling where ion channels are the primary drug targets or are off-targets for safety and toxicology. Other services on the increase include the capability to accept larger libraries for primary screening, various cardiotoxicity assessment offerings and ion channel directed chemical libraries. For the future screening services involving primary cells, cardiomyocytes and stem cells seem likely. on channels play key roles in regulating car- high-throughput screening (HTS) has hindered ion By Dr John Comley diac, neuronal and secretory tissues function channel exploitation compared to other target I and effective modulation of ion channel activ- classes. For this reason the cost of an ion channel ities impacts on many disease states. Ion channels data point (well screened) was one of the most rank among the most studied target classes (with expensive to generate within drug discovery. kinases and GPCRs) and their investigation is a Recent advances in automated patch clamping high priority in many organisations. However, the (APC) have, however, ensured that high quality direct measurement of ion channel function has meaningful safety pharmacology data can now be until recently been a difficult task to accomplish generated early in drug discovery and at higher and the lack of suitable technologies applicable to throughput than conventional manual patch Drug Discovery World Summer 2008 33 Ion channels:Layout 1 1/7/08 09:31 Page 34 Ion Channels drawn from late stage clinical trials due to these Figure 1: Ion channel drug discovery cardiotoxic effects; and secondly, it is now a rec- – technology preference ommendation to test for this liability under the ICH regulatory guidelines (S7B). Owing to the FIRST CHOICE – Primary Screening highly specialised nature of ion channel assays and FIRST CHOICE – Selectivity Profiling mandatory safety requirements for IND submis- ALTERNATIVE – Primary Screening sions, a significant number of fee-for-service ALTERNATIVE – Selectivity Profiling providers have set up operations to address the 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% growing outsourcing needs of ion channel % Responding research and off-target safety concerns. Services Manual patch-clamp Membrane binding assays offered range from fully GLP-compliant cardiac Automated patch-clamp (APC) Rubidium flux assays Fluorescent membrane potential assays Oocytes Fluorescent-based ion flux assays Field stimulation (eVIPR) safety hERG testing, early non-GLP hERG safety Flash luminescence-based Ca2+ assays Other technique FRET-based membrane potential assays testing, ion channel selectivity profiling, primary © HTStec 2008 screening and in vitro cardiotoxicity assessment. HTStec’s 4th Annual Ion Channel Trends 2007 Figure 2: Ion channel drug discovery survey and report1 in addition to monitoring ion – interest in outsourcing channel screening metrics, had a focus on the needs and requirements for outsourced ion chan- nel services. In this article we review some of the Very high 8% reports findings on outsourcing together with the High 13% ion channel services offerings of a number of fee- Perhaps 40% for-service providers. Low 25% Ion channel drug discovery services No interest 15% It is perhaps not surprising, with recent APC prod- 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% uct developments and user focus on direct meas- % Responding ures of ion channel activity, that the first choice © HTStec 2008 assay technology survey respondents were most interested in accessing at a fee-for-service Figure 3: Ion channel drug discovery – most important providers for ion channel drug discovery (ie pri- factors in choosing a fee-for-service provider mary screening and selectivity profiling) was auto- mated patch clamping. Acceptable alternative Data quality 4.80 technologies for primary screening were fluores- Access to ion channel targets not currently available in-house 4.41 cent membrane potential assays, automated patch Turn-around time 4.30 clamping and manual patch clamp. Acceptable Te c h nology (ie the methodology used to test compounds) 4.28 alternative technologies for selectivity profiling Price of service 4.25 were automated patch clamping and manual patch Expertise level of provider 4.19 clamp (Figure 1). Relevance of ion channel targets offered to safety assessment 3.91 The majority (65%) of current interest in out- Selectivity profiling within ion channel families (eg NaV, Kv) 3.50 sourcing ion channel screening for drug discovery Off-target profiling 3.46 was rated between ‘low’ and ‘perhaps’. Only 21% Total number of different ion channel targets offered 3.39 of survey respondents had either a ‘high’ or ‘very Already using this provider’s product and services 2.85 high’ current interest in outsourcing ion channel Ability to screen against other target classes (eg GPCRs) 2.69 screening for drug discovery (Figure 2). Proximity of service provider 2.30 Data quality was the main factor cited by survey 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 respondents when choosing a fee-for-service Rating SCORE 1 to 5 (where 1 = N/A; 2 = not important, 3 = somewhat important; 4 = important; and 5 = very important) provider for screening ion channels for drug dis- © HTStec 2008 covery. This was closely followed by access to ion channel targets not currently available in-house; technology (ie the methodology used to test com- clamping. One of the most popular applications of pounds) and then turnaround time (Figure 3). APC systems is the assessment of QT prolongation as a result of inhibition of the hERG potassium Cardiac safety hERG testing channel. Interest in this area is growing for two APC systems were preferred by survey respondents reasons; firstly, a number of drugs have been with- for non-GLP cardiac safety hERG testing (with 34 Drug Discovery World Summer 2008 Ion channels:Layout 1 1/7/08 09:31 Page 35 Ion Channels greatest interest in the MDC Ionworks Quattro/HT and MDC PatchXpress systems) and Figure 4: Cardiac safety hERG testing manual patch clamp for GLP cardiac safety hERG – technology preference testing (Figure 4). The majority of survey respondents undertake Non-GLP non-GLP cardiac safety hERG testing primarily in GLP house, while GLP cardiac safety hERG testing was 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% primarily outsourced (Figure 5). % Responding 41% of survey respondents rated their current Manual patch clamp Cellectricon Dynaflow Pro II interest in outsourcing cardiac safety hERG testing APC – Flyion Flyscreen /PatchBox APC – MCS Roboocyte APC – MDC Ionworks Quattro/HT APC – MDC PatchXpress as either ‘high’ or ‘very high’. A further 38% of APC – MDC OpusXpress APC – Nanion Port-A-Patch/Patchliner survey respondents rated their current interest in APC – Sophion QPatch16/HT Membrane binding assays Rubidium flux assays Use Other Technology outsourcing cardiac liability hERG testing as ‘per- No Preference N/A haps’ (Figure 6). © HTStec 2008 Price of service and turn-around time were the main factors cited by survey respondents when choosing a fee-for-service provider for cardiac lia- Figure 5: Cardiac safety hERG testing bility testing (Figure 7). – preferred approach In vitro cardiotoxicity assessment 15% Primarily outsourced Cardiotoxicity assessment is usually taken to refer 46% to the more direct measurement of delayed repo- 60% Primarily in-house larisation, eg prolongation of action potential 27% duration at 90% repolarisation (APD90) or QT Both in-house & 13% outsourced 6% interval. The hERG assay is a subset of cardiotox- Non-GLP 12% N/A icity assessment with hERG testing as a marker for 21% GLP delayed repolarisation and QT prolongation (the 0% 10% 20% 30% 40% 50% 60% 70% S7B guidance). Many fee-for-service providers % Responding © HTStec 2008 advocate a cardiac channel panel as the most com- plete assay for in vitro cardiac risk assessment. The majority of survey respondents are making Figure 6: Cardiac safety hERG testing greatest use of automated hERG patch clamp and – interest in outsourcing manual hERG patch clamp systems to undertake in vitro cardiotoxicity assessment. Other systems, eg Very high 15% hERG receptor binding methods and Purkinje fibre analysis were less widely used to undertake in vitro High 26% cardiotoxicity assessment. The Purkinje fibre assay Perhaps 38% assesses multi-channel effects and is suggested in Low 13% S7B guidance (Figure 8). No interest 9% The majority (57%) of survey respondents rate 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% the value of using in vitro cardiotoxicity
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