In the last few years, GPCR drug discovery has been transformed by the rapidly growing availability of 3D structures, better understanding of the atomistic mechanisms of signaling, and the development of giga-scale virtual spaces of drug-like compounds. This talk will describe two complementary computer-driven approaches to structure-based drug discovery of new GPCRs ligand chemotypes and new functionally-selective derivatives of known scaffolds. 

I present application of our fully-integrated proprietary R&D platform that enabled us, in 4 months, to move from structure prediction to in silico screening of a 10B molecule library, ending with biologically validated biased agonists for a POC GPCR. Our platform combines extensive pharmacological assay capabilities with ML (discussed by Victor Guallar in AI track) to determine protein conformations, gigadock ultra-large libraries in hours, and an ADMET-filter to assess druggability.

Septerna’s Native Complex Platform reconstitutes purified GPCRs, G proteins, and ligands into modular assemblies which retain their native structure, function, and dynamics. The GPCR Native Complexes are being utilized to unlock previously difficult-to-drug GPCRs through rapid iterative structure-based drug design and new paradigms for drug screening (including DNA-encoded library screens) for the discovery of a spectrum of therapeutic candidates with disease-relevant mechanisms-of-action including agonists, antagonists, and allosteric modulators.

GPCRs represent an important group of membrane proteins that play a central role in modern medicine. Unfortunately, conformational promiscuity hampers full therapeutic exploitation of GPCRs, since the largest population of the receptor will adopt a basal conformation, which subsequently challenges screens for agonist drug discovery programs. Herein, we describe a set of peptidomimetics able to mimic the ability of G proteins in stabilizing the active state of Gs- and Gq-mediated receptors. We were able to identify agonism pre-imprinted fragments for the examined GPCRs, and as such, they behave as a generic tool, enabling an engagement in agonist earmarked discovery programs.

With the guide of 19F NMR, we demonstrate the feasibility of enriching the populations of discrete states via a series of conformational-biased mutants. These mutants adopt distinct distributions among five states from inactive, intermediate, to the fully active states that lie along the activation pathway of adenosine A2AR receptor. Our study further indicates that the mutants present bias distinction on downstream signaling partners, implying their applications in biased drug development. 

Antagonism of CCR4 is currently being investigated by RAPT as potential treatment for allergic disorders mediated by Th2 driven inflammation. RPT193 can effectively inhibit CCR4-mediated Th2 chemotaxis and has successfully completed Phase I clinical trials where it has demonstrated good exposure and receptor occupancy after oral dosing and has shown evidence of efficacy in a Phase 1B trial in atopic dermatitis patients. The drug is currently in Phase II clinical studies for atopic dermatitis and asthma.

Psilocybin activates the 5-HT2A receptor to induce psychedelic subjective effects in humans and has shown antidepressant efficacy after a single administration. This presentation will highlight the use of an artificial intelligence (AI)-assisted/structure-based drug design approach to generate novel 5-HT2A agonists that mimic the polypharmacology of psilocin, the active metabolite of psilocybin, and promote both pharmacological and behavioral effects in animals consistent with antidepressant-like activity.

Olfactory receptors (ORs) were initially discovered in the nasal epithelium but have since been found in various other tissues. However, due to unique technical challenges in expressing functionally active ORs in vitro, they have remained understudied and underutilized. Considering that ORs make up 50% of the human GPCR-ome, they present an enticing drug target. In the course of our studies, we established an effective cell-based high-throughput screening (HTS) system and several orthogonal assays. This enabled us to identify new agonists and antagonists for OR51E1, an evolutionarily conserved OR associated with prostate cancer and the regulation of blood pressure.

Although gas structure has been known for years, we found a novel motif in gas that allows its interaction with ubiquitin, a key signal for receptor sorting to the degradation pathway. We also recently identified specific ubiquitination sites on gas that regulate its activity. This presentation will cover our recent data that bring to light a novel ubiquitin-based regulation of gas impacting GPCR signaling and trafficking for the fine-tuning of the cellular response.

The structural plasticity and dynamics of GPCRs are crucial for their activation and signal transduction. Understanding these dynamic conformational changes is important for developing drugs that target GPCRs with high specificity and low side effects. While the structures of some GPCR conformers have been characterized, the dynamics of these conformations are mostly unknown. Single-molecule fluorescence (SMF) helps to reveal the conformational dynamics of individual molecules in real time during GPCR activation.

Traditionally, G protein coupled receptors (GPCRs) were not considered to be regulated by the membrane potential. However, several studies from the last two decades demonstrated that several GPCRs were. I will present the evidence for such voltage dependence, the mechanism that underlies it, and the drug discovery implications of this novel allosteric modulation.