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The PD-L1/4-1BB Bispecific Antibody-Anticalin Fusion Protein PRS-344/S095012 Elicits Strong T-Cell Stimulation in a
Janet K Peper-Gabriel1, Marina Pavlidou1, Lucia Pattarini2
1Pieris Pharmaceuticals GmbH, Hallbergmoos, Germany.
Purpose:
While patients responding to checkpoint blockade often achieve remarkable clinical responses, there is still significant unmet need due to resistant or refractory tumors. A combination of checkpoint blockade with further T-cell stimulation mediated by 4-1BB agonism may increase response rates and durability of response. A bispecific molecule that blocks the programmed cell death 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) axis and localizes 4-1BB costimulation to a PD-L1-positive (PD-L1+) tumor microenvironment (TME) or tumor draining lymph nodes could maximize antitumor immunity and increase the therapeutic window beyond what has been reported for anti-4-1BB mAbs.
Experimental Design:
We generated and characterized the PD-L1/4-1BB bispecific molecule PRS-344/S095012 for target binding and functional activity in multiple relevant in vitro assays. Transgenic mice expressing human 4-1BB were transplanted with human PD-L1-expressing murine MC38 cells to assess in vivo antitumoral activity.
Results:
PRS-344/S095012 bound to its targets with high affinity and efficiently blocked the PD-1/PD-L1 pathway, and PRS-344/S095012-mediated 4-1BB costimulation was strictly PD-L1 dependent. We demonstrated a synergistic effect of both pathways on T-cell stimulation with the bispecific PRS-344/S095012 being more potent than the combination of mAbs. PRS-344/S095012 augmented CD4-positive (CD4+) and CD8-positive (CD8+) T-cell effector functions and enhanced antigen-specific T-cell stimulation. Finally, PRS-344/S095012 demonstrated strong antitumoral efficacy in an anti-PD-L1-resistant mouse model in which soluble 4-1BB was detected as an early marker for 4-1BB agonist activity.
Conclusions:
The PD-L1/4-1BB bispecific PRS-344/S095012 efficiently combines checkpoint blockade with a tumor-localized 4-1BB-mediated stimulation burst to antigen-specific T cells, more potent than the combination of mAbs, supporting the advancement of PRS-344/S095012 toward clinical development. See related commentary by Shu et al., p. 3182.
Insights
A novel bispecific molecule, PRS-344/S095012, combines PD-1/PD-L1 blockade with localized 4-1BB agonism. This approach enhances T-cell responses and shows potent anti-tumor activity, even in resistant models.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Checkpoint blockade immunotherapy shows promise but faces resistance in some tumors.
- Combining PD-1/PD-L1 inhibition with T-cell costimulation via 4-1BB agonism may overcome resistance and improve response durability.
- Targeting 4-1BB costimulation to the tumor microenvironment (TME) or lymph nodes could enhance efficacy and safety.
Purpose of the Study:
- To develop and characterize a bispecific molecule, PRS-344/S095012, that simultaneously blocks PD-1/PD-L1 and stimulates 4-1BB.
- To evaluate the in vitro and in vivo efficacy of PRS-344/S095012 in enhancing anti-tumor immunity.
Main Methods:
- Generation and in vitro characterization of the PD-L1/4-1BB bispecific molecule PRS-344/S095012.
- Assessment of target binding, pathway blockade, and T-cell stimulation in relevant assays.
- In vivo evaluation of anti-tumoral activity in a syngeneic mouse model using human PD-L1-expressing MC38 cells and transgenic mice expressing human 4-1BB.
Main Results:
- PRS-344/S095012 demonstrated high-affinity binding and effective PD-1/PD-L1 blockade.
- 4-1BB costimulation was strictly PD-L1 dependent, showing synergistic T-cell stimulation more potent than combined mAbs.
- The bispecific molecule enhanced CD4+ and CD8+ T-cell effector functions and demonstrated strong anti-tumoral efficacy in an anti-PD-L1-resistant model.
Conclusions:
- The PD-L1/4-1BB bispecific molecule PRS-344/S095012 effectively combines checkpoint blockade with localized 4-1BB costimulation.
- This novel approach demonstrates superior potency compared to combined antibody therapies.
- PRS-344/S095012 shows significant potential for clinical development in cancer immunotherapy.
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