Periodic Reporting for period 1 - GPR84 (Biased Agonism of GPR84 as a Novel Dual Anti-inflammatory and Pro-repair Mechanism)
Reporting period: 2021-07-05 to 2023-07-04
Orphan G-protein-coupled receptor 84 (GPR84) is a receptor that has been linked to cancer, inflammatory and fibrotic diseases. In our previous work, we reported DL-175 as a biased agonist at GPR84 which showed differential signalling via Gi/cAMP and β-arrestin, but which is rapidly metabolised. Herein, we describe an optimisation of DL-175 through a systematic structure–activity relationship (SAR) analysis. This revealed that the replacement of the naphthalene group improved metabolic stability and the addition of a 5-hydroxy substituent to the polar pyridine N-oxide head group, our newly discovered compounds, enhanced the potency for cAMP signalling by three orders of magnitude to low picomolar values. Neither compound showed detectable effects on β-arrestin recruitment up to the highest concentration tested (80 μM). Thus, the new GPR84 agonists displayed excellent potency, selectivity, high G-protein signalling bias and an appropriate in vivo PK profile that will allow investigation of GPR84 biased agonist activity in vivo.
Our optimization strategy in medicinal chemistry involved a multiple-parameter optimization (MPO) methodology for all newly designed and synthesized analogues of DL-175. This approach encompasses the design of new compounds with MPO scores that meet specific criteria, including: HBD≤1, TPSA≤75 Å, cLog P< 3, logD7.4 between 1 and 3, pKa<8. These criteria aligned with the requirements for favourable pharmacokinetic (PK) attributes and oral bioavailability. We also looked for correlations between binding affinity and key compound metrics such as ligand lipophilic efficiency (LLE) for all our derivatives. We also monitored the fraction of sp3 carbon atoms (Fsp3) and attempted to limit the number of aromatic rings (Property Forecast Index, PFI), which provided the favourable drug-like properties of compounds. Monitoring structure-property relationships (SPR) in this way, yielded two novel analogues with exceptional cAMP potency and a tremendous G-protein signalling bias compared to DL-175. Moreover, exquisite selectivity at GPR84 was observed in a panel against FFA1, FFA4 and CB2. In vitro metabolism studies of two new analogues showed enhanced MLM stability. In a PK experiment dosed at 10 mg/kg to a male C57BL/6J mouse, both compounds showed an appropriate ADME profile. Our two new compounds are the first drug-like biased agonist of GPR84 to serve as an in vivo pharmacological probe to perform key proof-of-concept experiments in relevant animal disease models.
Overall, the project has successfully achieved the following results:
1. Successful replacement of metabolically unstable naphthalene bottom groups of our previous compound DL-175 with highly stable aromatic rings.
2. Introduction of a strategically positioned hydroxyl group on the 3rd position of pyridine N-oxide, resulting in a 4000-fold increase in potency compared to DL-175, while remaining inactive in β-arrestin assays.
3. Discovery of the newly identified compounds AR-198 and AR-211, characterized by exceptional in vitro ADME profiles, in vivo PK profiles, high selectivity, and favourable oral bioavailability.
Overall, the project has successfully achieved the following results:
1. Successful replacement of metabolically unstable naphthalene bottom groups of our previous compound DL-175 with highly stable aromatic rings.
2. Introduction of a strategically positioned hydroxyl group on the 3rd position of pyridine N-oxide, resulting in a 4000-fold increase in potency compared to DL-175, while remaining inactive in β-arrestin assays.
3. Discovery of the newly identified compounds AR-198 and AR-211, characterized by exceptional in vitro ADME profiles, in vivo PK profiles, high selectivity, and favourable oral bioavailability.
We extend our appreciation to the Marie-Curie Actions for their support, which has paved the way for the identification and advancement of these promising two new highly potent and metabolically stable GPR84-biased agonist compounds, setting the stage for further exploration and inquiry. We've submitted a manuscript titled "Development of Highly Potent, G-Protein Pathway Biased, Selective, and Orally Bioavailable GPR84 Agonists" to the Journal of Medicinal Chemistry. Currently, the manuscript is undergoing the revision stage. Additionally, we are considering filing a patent application to protect our innovative work. Exceptionally potent compounds have been identified that guided the design, synthesis, and development of new GPR84 agonists with varying levels of bias. The structural variations of DL-175 have not only impacted potency but also the degree of signalling bias. This is a very important finding, and the second manuscript on this invention is currently in progress. The project's focus on the orphan G-protein-coupled receptor 84 (GPR84), linked to proinflammatory, cancer, inflammatory, and fibrotic diseases, holds immense potential for drug discovery. Activation of GPR84 has relevance in various disease models, highlighting the significance of our projects for drug development within academia and industry. Numerous industries' interest in this topic aligns well with the benefits offered by our research project.