Carving a niche in the realm of drug discovery

Molecular technologies such as genomics and proteomics have brought in a thorough make-over to early stage drug discovery. The strategic spotlight from the genomics technologies has gradually shifted focus to the cellular domain where the entire drug target interaction takes place. As a result, cell based screening provides promising potential to yield safer and non-toxic drugs. With the compelling need to improve the quality of hits that occur during the screening phase, it is critical that therapeutically relevant targets are identified, consequently bringing in savings on time and R&D costs.

Amidst the major high enabling technologies that have transformed many stages of drug discovery, cell based assays have shown good prospects in the areas of target validation and lead optimisation stages. The field of cytomics seems to hold the keys for a rational next generation drug design model through an amalgamation of technology and functional biology.

High content screening (HCS) brings to the forefront the ability to acquire multi-dimensional information rich content depicting the spatial and temporal activities of the cell. There has indeed been a revolutionary approach with respect to the development of HCS through multiplex assays along with new biological reagents and complementing data handling tools. Comparable developments in the reader and detection instrumentation have taken place to cope with the growing complexity of the biological assays. The concept of laboratory automation has been well accepted in life sciences but the current focus is on the ability to integrate automated liquid handling with robotics and detection on the same platform.

The industry has witnessed a gearshift with the implementation of HCS in different stages of drug discovery, in addition to the existing assay screening methodologies. The key areas of drug discovery that find HCS most useful are target ID and validation, secondary screening and compound profiling. HCS essentially utilises the biological system (living cell) as the fundamental platform and unites the same with the complimenting measurement, detection and informatics technology. Research reflects that the aforementioned approach enhances the existing focused library of compounds to have better stakes of making into clinical trials.

HCS as a driver has had a positive impact on the growth of cell based assays which has been a continuous evolving technology. The major benefit drawn from the HCS system as against HTS system is that it enables a speedy and a cost-effective approach to investigate a profile of compound libraries against the therapeutic targets identifying potential hits.

High content screening analysis has the ability to incorporate 100,000 compounds on a maximal scale with a major interest in generating a simple Yes/No readout with respect to compounds qualifying for possible hits. The enormous advantage that drug research can enjoy would be the availability of functional readouts by cataloguing the cellular activity profiles in every well thus reporting the cytoxicity, potency for a compound’s behaviour against the target. This evolutionary development of HCS from high throughput screening has taken drug discovery through a new dimension by setting the pace for simultaneous compound detection. HCS gives another value addition of providing a whole well analysis unlike HTS where many compounds may go undetected. On the other hand, comparing HCS with High content Analysis (HCA), the latter provides an in-depth cell content study with the corresponding pathway analysis that can catalyse the compound to hit process even faster. Figure 1 depicts the technology roadmap that has impacted early stage discovery with time. The HCS analysis takes the centre stage in addition to the HTS at present. While, the HCA technology concept presents a lucrative environment to the drug discovery platform, it is facing an uphill curve owing to high costs and some related technical challenges.

Scientific advances from the laboratory automation and miniaturisation have made sufficient inroads for high content screening to be implemented in primary screening and lead optimization. Constant improvements in assay methodologies are geared to keep pace with the surge of potential drug targets identified through the Omic revolution.

Integration of the different automation components into a consolidated system with maximal walkaway time is the most desirable trend sought by end-users especially for labor intensive tasks. Integration does bring a reasonable ROI with a one stop compact solution that would fulfill the cell based screening techniques. Key pointers to be wary about while making an allowance for automation would be to ensure compatibility between the instrumentation and corresponding software.

Many suppliers have brought in to the market detection systems that incorporate plate handling and automated liquid transfer. The aforesaid advancement is indeed very cost effective for the end-users and a vital competitive strategy model for vendors. The model works on the concept of integrating technologies that result in some key differentiating factors for strengthening their value-factured product line. This is a key strategy for suppliers to hold an advantageous position while gaining a higher market share.

Moreover, instrument and software compatibility issues have been resolved to a greater extent through the standardisation of protocols adopted by different manufacturers. In order to improve throughput and speed it is best advised for an open communication established between the different devices. There should be seamless transfer of assays in to the screening laboratory after the initial validation of targets in a HCS laboratory.

The spiralling growth with the fluorescence dyes, protein markers and labelling reagents through the readily available assay kits has also been an impetus for the switch from HTS to HCS. Quantum dot technology has also led to the introduction of some fluorescent reagents that work on Qdot nanocrystal concept owing to their unique optical properties.

The growing trend of HCS does face a price restraint through assay development and instrumentation costs. Data handling and management also require further sophistication given the technology enhancements to HCA in the future. HCA captures cellular subpopulations thereby giving more details on cytotoxicity early on and minimising late stage rejections. The decisive part in automation would be an effective data transfer to the installed LIMS system from the generated image data. The ability to archive and retrieve raw quantitative data and post processed image data are some of the other salient features required while choosing a HCS system.

The essential components in a HCS system are the plate reader and imaging systems. Flexibility is an important measure while deploying a reader to scan the entire well especially to acquire the best fluorescence without many artefacts. Laser scanning cytometers and fluorescence microscopy techniques have exhibited a good capacity to scan and detect an entire micro-well and convert the raw biological data to a more readable format with the help of new thresholding algorithms. Research shows that the readouts to a HCS device have been engineered such that there is maximum signal stability and the platform is open enough for automation inclusion. HCS plate readers offer reasonable sensitivity while reading across every well and have a leading edge against traditional HTS as it utilises lesser reagents and compounds. This also enables smaller data file sizes to maintain the throughput.

It is hoped that miniaturisation will reap phenomenal savings on reagent and consumables through lower volume and high density formats. Progressing from 96 plate format to 1536 high density format pharmaceutical companies are expecting to maintain the throughput and remain competitive. Presently 384 plate format has ushered in confidence amidst the pharmaceutical research community in terms of cost savings and efficiency apart from the bolstered support from the corresponding detection and dispensing instruments. The whole well analysis carried out in HCS with high speed reading devices has a good advantage over traditional microplate automation in the aspects of cell variability, edge effects etc.

Notwithstanding the evolving developments on the miniaturisation end, there are yet some important challenges to tackle with respect to low volume dispensing on cell based assays specifically. Low volume handling does have a challenge to grapple with in terms of counterbalancing the rising costs of reagents. Furthermore, the viability of the cell is a critical criterion along with the distinction in the cell behaviour to different environments. Cross contamination is the other important concern, considering the increased walkaway times owing to the automation concept.

To conclude, HCS is perceived to be in the early growth stage of the market lifecycle with many laboratories streamlining their budgets to purchase a HCS system within the next couple of years. There is definitely a lot of scope for vendors to collaborate with many bio-pharmaceuticals and academic laboratories. The cost factor should not be an impediment moving forward, as instrumentation and imaging suppliers are working towards meeting adequate demands of the end-users. Technological innovation has been the principal backbone guiding the development of imaging methods for a high content approach as multiple biomolecules can be tracked at once, yielding better reproducibility. With a lesser conservative outlook towards cell based assays along with the automation of sample handling processes and integration of various technologies, HCS is certainly carving a niche in the realm of drug discovery.