Domain’s Resources

- Due to its high and relatively specific expression on tumor-infiltrating Tregs, CCR8 represents an attractive novel target to derive novel immunotherapies.
- At Domain, we successfully discovered and patent-protected a mAb library of several dozen of antibodies with distinct and differentiated binding and activity profiles.
- This collection constitutes a unique source for the development of a best-in-class well-differentiated anti- hCCR8 depleting antibody for the treatment of cancers.
- Based on promising profiles, a set of anti-CCR8 mAb leads with distinct characteristics have entered late optimization phase (humanization, enhanced cytotoxic activity (i.e., ADCC, CDC, ADCP), …). Cell line generation will be initiated in Q1-2023.

High levels of prostaglandin E2 (PGE2) in tumors suppress anti-tumor immunity in the tumor microenvironment and contribute to tumor escape and disease progression. This effect of PGE2 is mediated through the activation of EP4R, a Gs protein coupled receptor activating cAMP signaling expressed by immune cells.
DT-9081 is a new small molecule, orally administered, highly selective antagonist of EP4R developed to overcome the immune-suppressive effects of PGE2, and to reverse the resistance to immune checkpoint blockers.
DT-9081 has demonstrated significant anti–tumor activity as monotherapy and in combination with immunotherapeutic agents in several syngenic murine cancer models (CT26 colorectal tumor model and MCA205 sarcoma model). These data are presented in poster #814:
”DT-9081, a selective EP4 receptor antagonist which synergizes with immune checkpoint inhibitors to induce complete responses in syngeneic murine
cancer models.”

The response to Immune Checkpoint Inhibitors (ICI) treatment can be limited by the implementation of resistance mechanisms by the tumor to escape from the host immune system surveillance. Combination strategies with agents designed to shut down these resistance pathways are highly desirable to generate a better anti-tumor efficacy and, of course, long-lasting complete responses.
Elevated levels of Prostaglandin E2 (PGE2), an eicosanoid synthesized from arachidonic acid by the inducible cyclooxygenase-2 (COX-2), exert strong immunosuppressive effect in the tumor microenvironment. Also, upregulation of COX-2 was shown in several types of tumors. Counteracting this immunosuppressive pathway have the potential to synergize with the anti-tumor effects of ICI. As the use of nonsteroidal anti-inflammatory drugs (NSAIDs) or COX-2 inhibitors (Coxibs) in cancer proved to be non applicable due to safety concerns, there is a need to develop safer alternatives, especially by inhibiting downstream targets. PGE2 immunosuppressive effects are largely mediated by the EP4 receptor, expressed on multiple immune cells. The development of antagonists of the EP4 receptor is thus a promising strategy to inhibit the PGE2-induced immunosuppression in the tumor microenvironment and to restore anti-tumor immunity.
Phase Ia clinical candidate DT-9081, a selective EP4 receptor antagonist, was designed to counteract the PGE2-immunosuppressive effects in the TME and to synergize with ICI. DT-9081 in vivo efficacy, in combination with ICI in murine syngeneic models, is presented.

Lead mAbs from Domain’s unique anti-hCCR8 collection were successfully humanized to deliver novel
antibodies having improved reactivity for HUT78 vs. chimeric ones. In addition, clear differentiating features were
observed with Domain’s humanized mAbs compared with competitors ones currently in the clinic. Amongst
these features, different epitope recognition and capacity to antagonize CCL1-induced receptor internalization
could represent key advantages. Finally, with the aim at optimizing depleting activities of Domain’s lead mAbs, Fc
variants were evaluated for Fc receptors binding and ADCC/ADCP activities. This characterization enabled the
identification of best Fc part for the final candidate selection.

We demonstrated that treatment with a depleting anti-mCCR8 mAb was able to translate into robust anti-tumor activity in multiple syngeneic models, with induction of potent and tumor specific long-term immunological memory. Moreover, the wide characterization of our diverse mAb library revealed distinct mAb cellular reactivity profiles, different epitope recognition modes (based on binding to different peptides with different post-translational modifications), subnanomolar antagonist activity, and insurmountable property with regards to CCR8 ligand CCL1.

By targeting not only mGluR4 but also mGluR7 and 8, and by exhibiting an improved oral PK profile, DT095435 is positioned as a second generation compound that should succeed in reaching clinical efficacy where Foliglurax narrowly failed.

This poster presents bioSens-All®️, a powerful and versatile pharmacological platform which is highly adaptable for hot topic targets such as Immune Checkpoint targets (Inhibitory & Stimulatory Immune Checkpoints).

Here, we describe a novel suite of enhanced bystander bioluminescence resonance energy transfer (ebBRET)-based biosensors that were used to define the signaling profiles of 100 therapeutically relevant human GPCRs in response to endogenous (or prototypical) ligands.

We present here several innovative BRET assays dedicated to inhibitory and stimulatory ICPs (PD-1, CTLA-4, 4-1BB), and developed by us.
The ICP platform set up here shows good accuracy & robustness and represents a solid & reliable technology for ICP dedicated drug discovery.

This poster presents the last generation of our proprietary platform bioSens-All®️ which is dedicated to the identification and characterization of immune checkpoint inhibitors.

This poster presents the characterization of a proprietary NPFF receptor antagonist as a game-changer and a promising therapeutic strategy to fight the current opioid crisis.

This poster illustrates a valuable BRET-based platform used to characterize RTK candidates regarding constitutive activity, real-time kinetics or impact of RTK mutations on signalling pathways.

co-authored with Explicyte, Bordeaux, France & Institut Bergonié, Bordeaux, France, this poster discloses an in-depth GPCR expression analysis from tumor microenvironment to dissect out mechanisms of resistance to immune checkpoint inhibitors.

This poster presents the complete characterization of Domain drug candidate benchmarked to EP4 antagonist molecules currently in the clinic and demonstrating a best-in-class potential.

This poster presents the profiling of DT095435, our pan group III mGluR PAM development candidate, as a potential new anti-dyskinetic treatment for Parkinson's disease.

This study served as a validation of the utility of the Gz/G15 large-spectrum biosensor for safety and systems pharmacology profiling. Moreover, our results support the use of this cell-based functional assay in high throughput receptor deorphanization and functional screening programs.