Background and Purpose:
Dopamine receptor agonists, particularly targeting the dopamine D
2L
receptor (D
2L
R), have been used to treat Parkinson's disease (PD). However, valvular heart disease and somnolence, mainly caused by activating the serotonin 5‐HT
2B
receptor (5‐HT
2B
R) and dopamine D
3
receptor (D
3
R), respectively, currently challenge their clinical use. Here, we aimed to develop a novel dopamine receptor agonist with superior therapeutic efficacy for PD, while minimising adverse reactions.
Experimental Approach:
Matsupexole, a novel nonergot dopamine receptor agonist, was evaluated by agonist activity for D
2L
R and a 6‐hydroxydopamine‐lesioned male rat PD model. To explore its adverse effects, the agonist activity for other receptors, including 5‐HT
2B
R and D
3
R, and the resulting porcine heart valve interstitial cell (PHVIC) proliferation and non‐rapid eye movement (REM) sleep induction in male rats were evaluated, in comparison with existing dopamine receptor agonists.
Key Results:
Matsupexole exhibited potent agonist activity for D
2L
Rs without inducing 5‐HT
2B
R activation or promoting PHVIC proliferation. Matsupexole demonstrated sustained efficacy in the PD model. In contrast, despite its strong D
2L
R agonist activity, cabergoline, an ergot dopamine receptor agonist, significantly evoked PHVIC proliferation. Reflecting its higher D
2L
R/D
3
R selectivity, matsupexole did not affect non‐REM sleep induction. Although pramipexole, a D
3
R‐favouring nonergot agonist, showed efficacy in the rat PD model, its effect was shorter in duration, and it strongly promoted non‐REM sleep. The stabilised interaction between Val190
5.39
in D
2L
R and matsupexole, but not pramipexole, further supports the higher D
2L
R/D
3
R selectivity of matsupexole.
Conclusion and Implications:Matsupexole is a promising future, potentially best‐in‐class dopamine receptor agonist for treating PD.