There have been clinical trials, unfortunately they do not get far due to them failing. Some examples are Pagaclone Ecopipam, and Propranolol. There we trials with Risperdol back in the 90s. Currently we are waiting on more from NOE-105 which is created specifically to target stuttering through targeted dopamine signaling neurons rather than full blown dopamine antagonists. It is also seeing success with treating Tourette’s. Seems like good stuff! Linky below https://clinicaltrials.gov/study/NCT05583955