A Perspective for Clinical Innovators at the Front Line of Prevention Science
At Alethium, we design clinical research with a clear view of the biological landscape. Few areas illustrate the need for scientific precision more than HIV prevention. On one side, we now have PrEP regimens that deliver levels of protection approaching functional sterilizing immunity when used correctly, including long-acting cabotegravir (Apretude) and twice-yearly lenacapavir (Yeztugo). On the other side, vaccine candidates that seemed promising only a decade ago have consistently struggled to translate immunogenicity into real-world efficacy.
Understanding this asymmetry is essential for how we design, operationalize, and communicate prevention studies. It also shapes how we evaluate the next generation of vaccine technologies as they begin entering early-phase trials.
The Virology Behind HIV’s Resistance to Vaccination
HIV remains an outlier in vaccine science because the virus exploits every known weakness in the adaptive immune system. Its genetic diversity is extraordinary, with rapid intrahost mutation rates and global variability across clades. A single immunogen cannot meaningfully represent that diversity, which explains the limited efficacy observed in trials such as the HVTN 702 update to RV144 and the mosaic-based Imbokodo and Mosaico programs.
The structure of the envelope glycoprotein further complicates vaccine development. Env is densely shielded by N-linked glycans that obscure neutralizing epitopes, and the conserved regions that broadly neutralizing antibodies target are conformationally transient. The immune system rarely generates these bnAbs without years of viral exposure.
Latency adds a uniquely unforgiving requirement: protection must occur immediately at the mucosal surface, before the earliest founder virions can integrate into resting CD4⁺ T cells. Once integrated, the provirus becomes immunologically silent and clinically permanent. For HIV, a vaccine cannot simply reduce symptoms or viral burden; anything less than near-instant sterilizing immunity still results in chronic infection.
Finally, the absence of natural sterilizing immunity means we cannot model success on a naturally occurring immune phenotype. Unlike pathogens, where convalescent immunity guides vaccine design, HIV offers no such template.
Why PrEP Achieves What Vaccines Have Not
The story is very different when we evaluate PrEP. Its success stems from its mechanism: PrEP bypasses antigen recognition entirely. It relies on placing potent antiretroviral agents at the site of exposure before HIV arrives, targeting viral processes too conserved for the virus to easily evade.
Cabotegravir, evaluated in HPTN 083 and HPTN 084, demonstrated superiority over daily oral TDF/FTC across diverse populations, largely because integrase inhibition during the first cycles of replication precedes latency formation. Lenacapavir, studied in the PURPOSE 1 and PURPOSE 2 trials, extended this paradigm to a twice-yearly injectable model by inhibiting capsid-regulated steps that HIV cannot mutate away from without profound fitness costs.
As long as tissue drug concentrations exceed protective thresholds, viral particles that cross the mucosa encounter a pharmacologic barrier before they can integrate. This timing advantage allows PrEP to achieve what vaccines cannot yet reliably do: block HIV during its narrow window of vulnerability.
The Vaccine Pipeline: What Is Beginning to Change
Despite historical setbacks, HIV vaccine science is undergoing a transformation. New platforms directly confront the structural and evolutionary constraints that defeated earlier approaches.
Germline-targeting bnAb lineage vaccines are one of the most promising strategies. The IAVI G001 and G003 trials, along with the eOD-GT8 and related programs, have shown that it is possible to activate the rare naïve B-cell precursors required to initiate bnAb maturation pathways. Sequential immunogen strategies, now being tested in early-phase human studies, are designed to guide these precursors through the complex maturation steps that natural infection accomplishes only slowly.
Parallel efforts focus on persistent cellular immunity. VIR-1388, currently in clinical evaluation, uses a modified CMV vector platform to generate unconventional, tissue-resident T-cell responses with the potential to eliminate infected cells before reservoir establishment. While efficacy data are years away, the conceptual grounding is strong and materially distinct from previous adenovirus-based platforms.
mRNA technology is also reshaping what is feasible. Moderna’s mRNA-1644 and mRNA-1644v2 programs are among the first formal attempts to use mRNA to deliver sequential engineered immunogens, leveraging germinal center biology in ways that protein vaccines could not sustain.
For the first time, these approaches seem capable of addressing HIV’s core immunologic challenges rather than skirting them.
Integrating PrEP and Vaccines in the Next Generation of Trials
The evolution of prevention tools means the old dichotomy of “PrEP versus vaccine” is no longer relevant. The future is almost certainly layered. PrEP will remain the backbone because it offers immediate, strain-agnostic protection grounded in predictable pharmacokinetics. Vaccines, once they demonstrate sufficient breadth and potency, will complement this protection rather than replace it.
For trialists, this creates both opportunity and complexity. PrEP must be incorporated into the standard-of-care prevention package for all vaccine efficacy trials, reducing endpoint incidence and requiring more sophisticated statistical strategies. Immunologic endpoints will become as important as clinical ones, particularly as we assess how vaccine responses interact with long-acting PrEP exposure.
A thoughtful prevention ecosystem will not assume that every modality must achieve absolute efficacy on its own. Instead, it will evaluate how combined approaches can achieve durable, equitable reductions in HIV incidence across diverse communities and geographies.
What This Means For Trials And For The Data Infrastructure Behind Them
As prevention tools become more powerful and more complex, the demands on the trials that evaluate them increase. Any modern HIV prevention trial must consider a background of highly effective PrEP as part of the ethical standard of care. This lowers the incidence of endpoints and forces studies to be larger, longer, or more innovative in design.
Layered strategies that combine long-acting PrEP with vaccine candidates or passive immunization require sophisticated protocol structures. Visit schedules may include different dosing intervals for drugs and vaccines, intensive pharmacokinetic and immunologic sampling windows, and dynamic adaptations based on emerging safety or efficacy signals. The volume and complexity of data increase markedly when a single trial tracks clinical outcomes, virologic parameters, detailed immunophenotyping, and adherence metrics across multiple arms.
This is precisely where a modern clinical data management system has to earn its place. A Clinical Data Management System (CDMS) that is built with advanced immunology and infectious disease in mind needs to handle deep longitudinal data, evolving visit schedules, complex derived endpoints, and integrations with laboratory systems, ePRO tools, and imaging or flow cytometry platforms. It must also support the operational realities of prevention trials that run across multiple regions, with varying standards of care and heterogeneous regulatory expectations.
Alethium’s Role In The Future Of HIV Prevention Research
Alethium does not sponsor HIV prevention trials, and we do not select which molecules enter the pipeline. What we do is build and operate the data infrastructure that allows those trials to run with clarity, agility, security, and safety.
Our experience in immunology and infectious diseases is invaluable, where timing, biomarker trajectories, and immune signatures matter as much as traditional clinical endpoints. That experience shapes how we think about HIV prevention. We ask, how do you capture the full picture of a participant’s prevention journey when they may be on twice-yearly lenacapavir, enrolled in a vaccine study, and receiving other standard-of-care interventions at the same time. How do you design a data model that can flex with adaptive trial designs and still remain transparent to regulators and data monitoring committees. How do you make it straightforward for sites to collect complex immunologic data without being overwhelmed by the mechanics of the system.
We are deeply excited about the science unfolding in HIV vaccines and PrEP, precisely because it demands this level of sophistication from the tools that sit underneath the trial. Alethium exists to make that complexity manageable. Our CDMS is designed so that trial teams can focus on the biology and the participants while trusting that their data capture, cleaning, monitoring, and reporting can keep pace with the science. In a field where timing, detail, and nuance determine whether a signal is real, that foundation matters.
HIV may remain one of the hardest problems in vaccinology, and PrEP may continue to be the most reliable prevention tool we have. The question for the next decade is how quickly we can learn from the interplay between these approaches. At Alethium, we ensure that when trial teams ask those questions in the clinic and in the field, their CDMS delivers reliable, timely, and secure results.
