Professional technology integration to support the entire R&D process

In the G protein-coupled receptor (GPCR) superfamily, there is a distinct group of members known as orphan receptors. While their endogenous ligands remained unknown for a long time, they harbor immense potential for drug development. GPR84 is a prime example. As an orphan receptor primarily expressed in immune cells (monocytes, macrophages, neutrophils) and microglia in the brain, GPR84 has recently been confirmed to respond to medium-chain fatty acids (MCFAs) and is deeply involved in the pathogenesis of inflammation, fibrosis, and metabolic diseases. From ulcerative colitis (UC) to non-alcoholic steatohepatitis (NASH), and from atopic dermatitis to acute respiratory distress syndrome (ARDS), GPR84 is rapidly emerging as an "invisible switch" linking metabolism and immunity. Leveraging its mature GPCR drug screening platform, ReqBio has successfully developed two functional cell models—GPR84/CHO and GPR84/β-Arrestin/CHO—providing global researchers with efficient and reliable tools for early-stage drug discovery.

I.GPR84: Evolution from "Orphan" to "Rising Star"

The GPR84 gene is located on human chromosome 12q13.13 and encodes a Class A rhodopsin-like GPCR. Although its endogenous ligands—medium-chain fatty acids (MCFAs) such as C10, C11, C12, and their hydroxylated derivatives—have been identified, GPR84 is still classified as a "Class A Orphan Receptor" due to the low potency with which these fatty acids activate the receptor EC 50 values are typically in the micromolar range). This low-potency natural activation suggests the potential existence of other high-affinity endogenous ligands yet to be discovered, or that the physiological function of GPR84 relies more heavily on synergistic signaling within specific microenvironments.Notably, inflammatory stimuli (such as LPS and TNFα) can significantly up-regulate the expression of GPR84. Once activated, GPR84 further promotes the secretion of cytokines by macrophages and enhances chemotaxis and phagocytosis. This positive feedback mechanism makes GPR84 a critical amplifier of the inflammatory cascade.

II.GPR84 Signaling Transduction: Diversified Downstream Pathways

Similar to many GPCRs, the activation of GPR84 can transmit information through multiple signaling pathways. Different agonists (including natural MCFAs and synthetic ligands) can induce biased signaling, preferentially activating one downstream pathway over others. The currently identified signaling pathways for GPR84 include:

①Gαi/o Pathway: Inhibits adenylate cyclase and reduces cAMP levels; this is the most classic signaling mode of GPR84.

②Gα15/16 Pathway: Activates phospholipase C (PLC) and increases intracellular calcium ion concentration.

③β-Arrestin Pathway: Recruits β-Arrestin proteins, mediating receptor internalization, desensitization, and non-G protein-dependent signaling.

This multi-pathway and bias-capable characteristic provides drug developers with rich regulatory dimensions: biased agonists can selectively activate beneficial pathways (such as anti-inflammatory signaling) while avoiding adverse effect pathways, whereas antagonists can block pathological inflammatory amplification effects.

III. Drug Development Targeting GPR84: From Laboratory to Clinic

Due to the critical role of GPR84 in various inflammatory and metabolic diseases, substantial progress has been made in the development of targeted drugs. Currently, several small-molecule agonists and antagonists have entered clinical trial stages, with indications covering Alstrom syndrome, atopic dermatitis, ulcerative colitis (UC), and diabetic neuropathic pain.

It is noteworthy that the clinical development of GPR84 is currently concentrated on small-molecule drugs, which aligns with its structural characteristics as a GPCR and its advantages in oral bioavailability. With the first GPR84 antagonist entering Phase 3 clinical trials, the druggability of this target has been preliminarily validated.

Ⅳ. Accelerating GPR84 Drug R&D: ReqBio’s One-Stop Cell Models and Data Advantages

In the early stages of GPCR drug discovery, cell models that are stable, sensitive, and fully functionally validated are crucial for screening lead compounds and evaluating the efficacy of candidates. Targeting the GPR84 receptor, ReqBio has developed two core cell models to cover different detection platforms and screening requirements.

ReqBio’s GPR8 Series Cell Models:

Validation Data and Advantage:

1.CHO-K1 Human GPR84 Cell Line(RQP71595)

Figure 2. HTRF cAMP Assay with GPR84 CHO (C32)

This figure illustrates the dose-response curve measured in the GPR84/CHO cell line (Clone C32) using the HTRF (Homogeneous Time-Resolved Fluorescence) cAMP detection platform. The specific advantages are analyzed as follows:

Summary of Core Product Advantages:

①Frontier Target: GPR84 is an emerging target at the intersection of inflammation and metabolism. With a competitive landscape that is not yet overcrowded, it holds high R&D value.

②Reliable Models: Rigorous functional validation (cAMP inhibition) ensures a specific response via the Gαi signaling pathway.

③ Mature Platform: HTRF is the gold-standard technology for GPCR drug screening; the resulting data can be directly utilized for academic publication or IND filing.

④Flexible Adaptation: We provide various host cells, including CHO and HEK293, along with multiple detection modes such as cAMP, Calcium flux, and β-Arrestin to meet the needs of different R&D stages.

⑤Ready-to-Use Products: Our cell models undergo strict clone selection and cryopreservation quality control. They are ready for immediate experimentation upon arrival, shortening the R&D cycle by 2–3 months.

Ⅴ.Conclusion

The evolution of GPR84 from an orphan receptor to a clinically validated target is a microcosm of modern drug discovery. With a deeper understanding of its signaling mechanisms and the advancement of the first Phase 3 clinical drug, GPR84 is poised to yield blockbuster therapies in fields such as inflammatory bowel disease (IBD), fibrotic diseases, and metabolic syndrome. ReqBio will continue to cultivate frontier GPCR targets, providing high-quality cell models and detection services to empower the discovery and development of innovative drugs worldwide.