Please have a read of our frequently asked questions below. Alternatively, contact us if you require further information:


What is the sensitivity of the Cell Microarray technology?

Ligand-target interactions of 10 micromolar can be detected in the absence of any amplification strategy. This is more than adequate for most studies; however, amplification strategies can be employed when needed in order to detect lower affinity interactions.


How many proteins are represented in the Retrogenix Cell Microarrays?

There are currently over 6,200 clones in the micorarrays all encoding full-length human plasma membrane monomers, heterodimers or secreted proteins. This represents around 80% of all unique proteins across our libraries. Where possible, canonical or longest isoform clones have been included, along with many alternative isoforms/splice variants that have also been incorporated. A full list of proteins in the set is available on request to researchers who are looking to use the cell microarray service.

The clone set can be expanded to incorporate additional proteins when a particular protein family or subset is of interest. Please contact the Retrogenix team to discuss your specific requirements so a bespoke project can be designed for you.


What cells are used in the Cell Microarray system?

Currently the Retrogenix protein library is expressed in human HEK293 cells in order to ensure correct post-translation modifications, folding and localisation in human cells and produce a physiologically-relevant system. Should another system be required for your project then please get in touch to discuss the possibility of a bespoke consultancy project to develop and optimise a new system.


What type of molecules can be screened using the Cell Microarray technology?

Any ligand can be screened for interactions against the Retrogenix cell microarrays as long as a suitable system exists to detect gain-of-binding. Retrogenix has successfully found receptors and targets for labelled small molecules, antibodies, antibody fragments (such as scFvs and Fabs), antibody-drug conjugates (ADCs), viruses and virus-like particles (VLPs), labelled or tagged protein and peptide ligands, labelled whole cells (such as CAR-T cells) and plasma samples from cancer patients.


Can Retrogenix screen ADCs?

Yes. We can screen antibody-drug conjugates (ADCs) as our protocols allow us to fix the cells prior to assessing binding to each over-expressed target. As the cells are not alive, the toxicity of the ADC payload does not affect the results.


How much purified antibody is required for a screen?

This depends on the molecular weight and the design of the study, however, typically between 100ug to 4mg will be required.


Which protein tags or labels are compatible with the Cell Microarray technology?

As long as we can detect gain-of-binding to the cells in our microarrays we can screen any molecule. We have vast experience with anti-His, anti-Flag, anti-V5, anti-Fc, biotin-streptavidin, directly fluorescently tagged, and radiolabeled molecules.

We are also able to optimise the procedure for a new method should it be necessary to use a detection system that we have not encountered before. Please get in touch if you have a specific requirement.


Is endogenous expression of the target protein in HEK cells an issue?

A background screen is against untransfected HEK cells is always carried out in order to check that endogenous expression (and therefore binding) of the target will not be an issue.

Approximately 90% of molecules progress past the background screen and onto the full screens against the complete set of >5,500 individually over-expressed proteins. In cases where background binding will pose a significant challenge we will discuss the option of modifying or terminating the study prior to screening in order to avoid investing in a screen that would have little chance of success in identifying target receptors.


We are only interested in one class of proteins – do we have to undergo a full screen?

It is possible for Retrogenix Scientists to customise arrays to screen only certain classes of plasma membrane or secreted proteins. Please contact our scientists to discuss this.


How will I know how the study is progressing?

The Retrogenix team will share the results of the background screen before progressing to the full screen. We will also keep you updated of how the project is progressing during the full primary and confirmatory screens.


Who owns the data and the IP generated when a new drug target is identified?

You do. Retrogenix does not lay claim to any IP generated from its screening service unless there has been prior agreement to share IP.


Can I publish the results?

Yes please! The data and any associated intellectual property (IP) belong to you. We fully support the publication of results from a screen and can assist with writing the relevant methods and results sections of the paper or patent. We also love to talk about the great results we get from our studies, but we only discuss, present or publish results when we have express permission to do so. Please see our resources section for some of our recent publications, poster presentations and case studies.


How many hits will we typically get back from a screen?

Non-specific and non-reproducible hits are weeded out by our rigorous screening process. Therefore, if the target(s) for your molecule is in the Retrogenix library, you should expect one, possibly two, highly specific hits. Often multiple hits represent variants of the same protein receptor that are in our library. This can act as an additional positive control, providing additional confidence that the results are specific.

Unlike other screens which produce multiple hits (sometimes even hundreds) that then need investigating, the specificity of the Retrogenix screen only returns one or a few hits that are specific and reproducible.


What data will I receive?

A full report presenting and interpreting the results of the screens is provided at the end of a standard study. On request, members of the Retrogenix team can also present and discuss the results via a web meeting.


Who validates the data from a Retrogenix screen?

We run a confirmation screen in-house as standard to ensure that the results are specific and reproducible before presenting all the data and discussing the results with the client. Further target validation work can be undertaken by Retrogenix Scientists as a follow up study; for example, Retrogenix can validate the findings using a FACS-based approach.


How long does a screen take?

Full projects typically take around 6-8 weeks from when we receive materials through to delivering the results and data package. Some high throughput lead selection projects are suitable for our ‘cut-down’ service which takes as little as 3 weeks. Longer lead times (for example 12 weeks) may be required for some studies including projects where a new detection method is being used as this will need to be optimised with the Retrogenix technology.


How much does a screen cost?

This depends on the number and type of molecules to be screened, the detection system and the screening format. Please get in touch with a member of our team to discuss your project.


Does screening multiple molecules reduce the price of using the Cell Microarray technology?

Larger screens allow us to organise our lab resources more efficiently so there is a cost reduction for multiple molecules that are run in simultaneously.

Savings can also be made by arranging an allocation of molecules to be screened over a fixed period of time, for example, a commitment to screen twenty molecules over a 12 month period. This has benefits for groups that are continually discovering or evaluating new molecules as they can be sent for screening when they are ready. In addition, guaranteed resource will be applied to these projects.


What cost savings can a Retrogenix screen provide?

An analysis by one of our pharmaceutical clients estimated that in-house methods required around 10x the investment of a Retrogenix screen to produce the same number of successful results.

The massive savings are mainly due to the high success rates that Retrogenix achieves – estimated to be around 4x greater than the chances of identifying a specific target using IP/MS approaches – plus the lab and personnel costs associated with carrying out the work in-house.

Can I request a follow-on validation study after results have been delivered?

Absolutely. We don’t require commitment to a follow-on validation study up front when you book your project, giving you the flexibility to appraise your initial results first before deciding if validation is required or beneficial.

We can also usually use materials which are already available to us at the end of your main screen to carry out validation, negating the need for you to produce and ship further samples to our UK labs.

Are screens performed on live or fixed cells?

Either! Contrary to conventional thinking we have regularly observed better results and clearer target:ligand binding on fixed cell screens so perform fixed cell screens as standard. Depending on the study, live cell screening can be more appropriate and will be conducted.


What does Charles River’s acquisition of Retrogenix mean for me?

As part of Charles River, Retrogenix will continue to provide, and develop further, our capabilities, whilst providing our clients with easier access to a wider range of skills and capabilities to support their programmes.

We will continue to operate from our High Peak UK facilities, and there will be no changes to our uniquely skilled workforce.

For those currently undertaking or planning projects with Retrogenix, your current business development and scientific contacts will remain the same, and your existing agreements will remain valid.


How do I access Charles River services through Retrogenix?

Through Retrogenix, clients now have the option to connect active projects with the expanded service pipeline of Charles River. Your project manager will be able to offer further, personalised guidance.


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