Introduction: Tobacco smoking is an insufficiently addressed health burden among people living with HIV. The Reduce tobacco use in people living with HIV in Switzerland (RETUNE) trial tests the effectiveness of offering a menu of nicotine substitute products, including e-cigarettes, nicotine pouches, and nicotine patches, on tobacco smoking cessation rates. This a priori planned internal pilot aims to assess the trial processes, in particular the delivery of the intervention, and its acceptance by participants.

Methods: RETUNE is a pragmatic, randomized, multicenter trial using the 'Trials within Cohorts' (TwiCs) design embedded in the Swiss HIV Cohort Study. Participants are people living with HIV who are part of the cohort and smoke. Following the TwiCs design, participants can accept one of the offered intervention products or refuse all of them, after being randomized to the intervention group. This internal pilot study included the first 200 RETUNE participants randomized between February and September 2025. We report the acceptance rate and participants' experiences with the intervention products, based on trial data and additional questionnaires.

Results: Of the 98 participants randomized to the intervention group, 53 accepted a nicotine substitute product while 45 declined the intervention. The majority chose e-cigarettes (31/53; 59%), one-third chose nicotine patches (17/53; 32%), and four participants chose nicotine pouches (4/53; 8%). The most common reason for declining all offered products was no interest in quitting tobacco smoking (34/53; 64%). Overall, 37/53 (70%) intervention participants completed the pilot study survey. Most (27/37; 73%) continued the initially chosen product; the remaining changed the product, the nicotine concentration, or the flavor; however, no one stopped the smoking cessation intervention entirely.

Conclusions: The results of this internal pilot support the feasibility of the RETUNE trial. The observed acceptance rate was similar to our estimate. E-cigarettes were the preferred product. We are continuing recruitment for the RETUNE trial.

Clinical trial registration: The study is registered on the official website of ClinicalTrials.gov.

Identifier: NCT06789692.