Abstract Body (Do not enter title and authors here): Introduction: Guidelines recommend quadruple therapy (angiotensin receptor blocker-neprilysin inhibitor [ARNI]), beta-blocker, mineralocorticoid receptor antagonist (MRA), and sodium-glucose co-transporter 2 inhibitor [SGLT2I]) as the cornerstone of heart failure (HF) with reduced ejection fraction (HFrEF) management. Yet, guidelines do not propose a specific order of initiation and titration (or “sequencing strategy”) of these agents, due to the absence of trial evidence.

Aims: To model the 1-year efficacy and harms of proposed HFrEF quadruple therapy sequencing strategies using a microsimulation model.

Methods: We conducted an individual-based state-transition microsimulation modeling study to compare the 1-year cumulative incidence of death, total HF hospitalization, and adverse events with 6 different HFrEF medication sequencing strategies (emulating 2 different traditional strategies, 2 two-drug combinations, a "cluster" strategy, and four-drug "simultaneous" strategy), each with two versions (weekly or biweekly medication adjustments), applied to treatment-naïve outpatients with HFrEF. We modeled death as an incidence at 1 year, and total HF hospitalization (first and recurrent events) and adverse events (bradycardia, hyperkalemia, hypotension, and renal impairment) as incidence rates per 100 patient-years.

Results: At 1 year, an estimated 15.5% died without treatment compared to 6.9% with the traditional sequence adjusted biweekly, and 5.2-6.3% with other sequencing strategies. Similarly, the HF hospitalization rate decreased from 32.8 per 100 patient-years with no treatment to 11.1 per 100 patient-years traditional sequencing adjusted biweekly, and 6.9-9 per 100 patient-years with other strategies. The incidence rates of medication-related adverse events per 100 patient-years were: hypotension (5.8-6.9), renal impairment (4.6-6.0), bradycardia (2.9-3.2), and hyperkalemia (approximately 0.5).

Conclusions: For treatment-naïve outpatients with HFrEF, pharmacotherapy sequencing strategies that started 2 to 4 medications on the first visit reduced the risk of death and hospitalization at 1 year compared to a traditional sequencing strategy. Weekly medication adjustments did not outperform biweekly adjustments when >=2 medications were started on the initial visit. These findings can inform clinicians and policymakers in developing HFrEF medication optimization programs with sequencing strategy protocols that fit the local practical context.