ISR Platform



Today, biologics represent one of the fastest growing markets within the pharmaceutical industry.

The pipeline of biological drugs is growing at a rapid pace with a global market expected to reach approximately 380 billion USD in 2024.(1)

In order to bypass gastric metabolism, biologics are usually designed for the parenteral route of administration. However, this solution is cost intensive and tends to lower patient compliance.

On that note, subcutaneous injection offers a variety of benefits including self-medication, shorter administration time and therefore a better adhesion to the treatment as well as reduction of costs.

Today, 4,959 clinical candidates (2) are being investigated for subcutaneous routes, either new candidates or approved therapeutic products currently available for parenteral routes.

However, subcutaneous injection comes with some drawbacks.

Part of them are side effects that can dramatically decrease patient compliance making treatments less effective than they are supposed to be.

The most reported adverse effect upon injection of a biologic drug is an injection site reaction.

It is commonly known that animal models, albeit still widely used, cannot provide enough reliable data directly translatable to the human condition. Therefore, we are facing a lack of R&D solutions that closely mimic or display human functions and metabolism to better predict those types of side effects.

There is an urgent need to improve the way drugs are developed that biotech companies are working restlessly to meet.

With 10 years of expertise in generating actionable human data through a range of living immunocompetent human skin models, Genoskin aimed to try and fill this gap. Combining organ-level assays with single cell analyzes and artificial intelligence is an innovative solution that led to the creation of a brand new platform of services.

Today, with the ISR platform, Genoskin provides bio pharmaceutical companies with a unique and patented human based-tool to support the development of new drugs that do not trigger injection site reactions, a real challenge in the field.

What else could better predict human reactions than an actual part of a human being?

But first, let’s dive a bit into injection site reaction characteristics.

Injection site reactions are triggered by a mast cells-specific receptor.

Frequently, the injection of some therapeutics formulation can lead to a fast and local inflammatory response characterized by swelling, erythema and pain.

Such a reaction is commonly known as injection site reaction (ISR), the most common reported adverse effect upon injection of a biologic drug (3), (4).

Immediate ISR are pseudo-allergic reactions recently reported to be triggered through a mast cells receptor, MRGPRX2, the human ortholog to the mouse MrgprB2 (5).

MRGPRX2 was found to be activated by a broad range of cationic substances such as neuropeptides, but also therapeutic drugs including beta-lactam antibiotics, chemotherapy agents, among others (6).

Delayed injection site reactions (happening within days post injection) can also be observed and are known to be driven by additional inflammatory mechanisms, most notably the recruitment of peripheral blood immune cells at the site of injection.

Therefore, identifying new drug-candidates that do not trigger mast cell dependent or independent ISR-like inflammatory responses ahead of clinical trials becomes crucial to ensure patient safety, comfort and compliance toward an injectable treatment.

How mast-cells are involved in injection site reactions.

Discovered over a century ago by Paul Ehrlich (7), mast cells are becoming a hot topic with more than 180,000 publications over the past 6 years (8).

They play a central role in allergic reactions and have an important implication in the defense against pathogens. Therefore, they are an asset in developing new drugs or improving existing ones.

To date, research on mast cells can be performed using rodent cell lines or human cell lines as well as human primary mast cells derived from peripheral blood (PB) or cord blood (CB). Mast cells can also be studied in situ, directly in living immunocompetent skin models.

Mast cells express various activatory receptors (some of them are described in Figure 1), and scientists are getting better at understanding the metabolism and molecular mechanisms behind their biological functions.

We describe below two key mast cell receptors involved in allergic and pseudoallergic reactions.

human primary connective tissue-type mast cells and some of its receptors

Figure 1: Mast cells express a broad range of receptors involved in acute allergic reactions as well as defense mechanisms against pathogens. Here, we illustrated FcRI, MRGPRX2, C2R and C5R, KIT and FcRIIa.

The high affinity IgE receptor (FcRI).

Mast cells are known for their implication in IgE-mediated disorders through their expression of the FcRI.

IgE antibodies can be found bound to FcRI circulating in the peripheral blood. The contact between an antigen and surface-bound IgE (specific of such antigen) will result in the crosslinking of FcRI and activation of mast cell degranulation. This will then trigger the release of pre-stored inflammatory mediators (9) such as histamine and proteases, and the secretion of de novo mediators9 such as cytokines or eicosanoids (10).


Briefly presented earlier, Human Mass-related G protein-coupled receptor X2 (MRGPRX2) is strongly present in connective tissue-type mast cells mainly located in the human skin. MRGPRX2 has been recently described as a major player in immediate injection site reaction, a severe hypersensitivity reaction that occurs in a significant number of patients treated with biological drugs. IgE-dependent or MRGPRX2-dependent mast cell activation typically results in an increase of vascular permeability, formation of oedema which will lead to different kinds of symptoms depending on the location of the mast cells. In the skin, typical symptoms will be urticarial reaction with itchiness and pain.


Genoskin’s new answer to the injection site reaction challenge is based on a three-step platform which aims to support safer drug-candidate development.

The three levels of complementary assays allow better characterization of mast cells-dependent and independent inflammatory reactions:

in situ mast cells degranulation

In situ mast cells degranulation.

high throughput mast cells assays

High-throughput mast cell assays.

MRGPRX2 activation

MRGPRX2 activation.


Upon subcutaneous injection in an ex vivo human and immunocompetent skin model: determination of the inflammatory signature of a drug.

Cytokine release assays, artificial intelligence-assisted mast cells degranulation scoring, analysis of genes differentially-expressed by mRNA sequencing and multiplex imaging of skin-resident immune cells activation status can be performed on healthy skin from donors of different gender, age and ethnicity, allowing more predictable clinical data ahead of clinical trials.


With in vitro assays performed on human primary connective tissue-type mast cells.

In vitro mast cells degranulation assays allow a better understanding of whether a given therapeutic molecule or formulation can directly activate human primary mast cells. The data generated is then correlated with the analysis performed at the organ level.


With in vitro assays targeting precisely MRGPRX2.

Here, we can take a closer look and screen drug-candidates or formulations to identify whether they behave as an agonist of MRGPRX2.


5. McNeil BD, Pundir P, Meeker S, Han L, Undem BJ, Kulka M, Dong X. Identification of a mast-cell-specific receptor crucial for pseudo-allergic drug reactions. Nature. 2015 Mar 12;519(7542):237-41. doi: 10.1038/nature14022. Epub 2014 Dec 17. PMID: 25517090; PMCID: PMC4359082.
6. Porebski G, Kwiecien K, Pawica M, Kwitniewski M. Mas-Related G Protein-Coupled Receptor-X2 (MRGPRX2) in Drug Hypersensitivity Reactions. Front Immunol. 2018 Dec 20;9:3027. doi: 10.3389/fimmu.2018.03027. PMID: 30619367; PMCID: PMC6306423.
7. Wang et al. “The return of the mast cell: New roles in neuroimmune Itch biology”JID 140-5 P945-951, 2020.
9. Krystel-Whittemore, Melissa, et al. “Mast Cell: A Multi-Functional Master Cell.” 2016,
10. Amin K. The role of mast cells in allergic inflammation. Respir Med. 2012 Jan;106(1):9-14. doi: 10.1016/j.rmed.2011.09.007. Epub 2011 Nov 22. PMID: 22112783.

Depending on your needs, assays can be performed starting at any level of the platform. Genoskin team of experts will guide you & provide you with a custom study plan to answer your question.

For more information about our ISR platform and its application, please contact us.

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