Highly potent, brain‐penetrant EP 2 receptor antagonists for the treatment of permanent focal cerebral ischaemia in male and female mice

Abstract Background and Purpose Cerebral ischaemia is a leading cause of death in older adults and imposes a substantial global economic burden. Recent studies indicate that inhibiting the Gα s ‐coupled EP 2 receptor reduces ischaemic brain injury by modulating neuroinflammation. However, these findings derive from the transient middle cerebral artery occlusion (tMCAO) model, which represents only a small subset of large‐vessel occlusion (LVO) cases with successful recanalisation. Experimental Approach We characterised the pharmacokinetic parameters of selective EP 2 antagonists CJ‐18, CJ‐19 and CJ‐21 that we recently developed. We evaluated their therapeutic efficacy in mice subjected to permanent MCAO (pMCAO), a model that more accurately reflects the majority of LVO cases, and assessed the impact of EP 2 inhibition on brain injury and inflammation. Finally, we examined the effects of EP 2 inhibition in neuron–glia mixed cultures exposed to oxygen–glucose deprivation (OGD) without reoxygenation. Key Results After systemic administration in mice, new compounds exhibited favourable plasma half‐lives and brain penetration. In the pMCAO model, treatment with EP 2 antagonists significantly reduced brain infarction in both male and female mice, in a dose‐dependent manner, whilst improving sensorimotor performance without affecting muscle strength. These benefits were accompanied by reduced neuronal death, lowered pro‐inflammatory cytokines and attenuated reactive gliosis within the ischaemic penumbra. In addition, EP 2 inhibition by CJ‐18 conferred marked neuroprotection in neuron–glia co‐cultures exposed to prolonged OGD, preserving neurite integrity and postsynaptic density. Conclusions and Implications This proof‐of‐concept study supports our drug‐like EP 2 receptor antagonists, particularly CJ‐18, as potential treatments for permanent focal cerebral ischaemia.