Next-Generation HIV-1 Therapeutics in Co-Endemic Settings.

The development of next-generation HIV-1 therapeutics, including ultralong-acting antivirals, novel mechanistic classes, and curative immunotherapies, promises to overcome the limitations of lifelong, daily antiretroviral therapy (ART). However, the real-world efficacy of these treatments depends on the complex epidemiological landscapes in which they are used. In South America, HIV-1 epidemics intersect hyperendemic arboviruses, including dengue, Zika, chikungunya, and yellow fever, and regionally isolated pathogens, such as mammarenaviruses. These co-infections cause profound episodic immune activation and organ dysfunction that alter drug pharmacokinetics, disrupting healthcare access and adherence. These factors can compromise ART efficacy, promote resistance, and influence latent reservoir dynamics. This review synthesizes clinical and translational evidence of this intersection. We evaluate how emergent agents, such as capsid inhibitors (lenacapavir), long-acting injectables (cabotegravir/rilpivirine), maturation inhibitors (GSK3640254), and broadly neutralizing antibodies (bNAbs), perform in the context of co-endemic viral challenges. Specifically, we argue that therapeutic development must become "co-infection-aware" to progress toward a cure and achieve durable HIV-1 control. We provide a translational roadmap that explicitly incorporates co-infection endpoints into clinical trials, develops preclinical models that better reflect real-world viral exposures, and prioritizes implementation strategies that remain effective in the case of recurrent outbreaks. Integrating regional viral ecology into HIV-1 therapeutic research is therefore a necessary step toward developing interventions that are durable and effective on a global scale.