Refillable Implant Shows Promise in Preventing HIV

In the ongoing battle against HIV, researchers are constantly seeking innovative approaches to prevent transmission. One such promising development is a refillable implant that delivers antiretroviral medications, offering a potential breakthrough in HIV prevention. This article explores the challenges associated with existing methods of pre-exposure prophylaxis (PrEP) delivery. It also introduces the refillable implant concept, discusses the findings from animal research, and highlights the potential implications of this novel approach.

HIV test

The Promise of a Refillable Implant

When it comes to PrEP, the cornerstone of HIV infection prevention, adherence to medication schedules can be challenging for many patients. The new refillable implant offers a hassle-free way to continuously deliver antiretrovirals for up to 20 months, making PrEP easier to use for individuals who struggle with pill or injection adherence. By ensuring consistent drug delivery, the implant aims to reduce the chances of HIV transmission.

Current PrEP Administration Methods

The two main methods of PrEP administration are oral medication and injectable treatments. Oral PrEP, such as Truvada and Descovy, consists of a single tablet containing a combination of antiretroviral medications. While highly effective when taken daily, adherence can be an issue for some individuals. Injectable PrEP, known as Aperture, provides an alternative for those who have difficulty adhering to a daily pill regimen. Administered via injections every two months, it has shown slightly higher effectiveness compared to oral PrEP.

Testing the Implant: Findings and Results

To explore the potential of a refillable implant, researchers conducted animal testing using medical-grade titanium implants placed just below the skin. In a study involving male rhesus macaque monkeys over a 20-month period, the implants successfully diffused an experimental antiviral medication called islatravir (ISL) into the bloodstream. The research team concluded that the circulating blood concentrations of ISL matched the desired protective levels seen in monkeys receiving ISL via weekly pills. Moreover, the implanted monkeys exhibited full protection against simian HIV exposure through both the rectum and vagina, with no safety or tolerance issues.

Future Directions and Clinical Trials

The promising results from animal research have laid the foundation for human trials. The next steps involve determining the lowest effective dose for continued protection and evaluating the implant’s effectiveness against different routes of HIV infection, including sexual and injection drug use. Researchers are currently preparing for human trials, with hopes of clinical testing within the next three years. If all goes well, the refillable implant could potentially be available within five years.

Expert Commentary and Potential Implications

Dr. Michael Horberg, an HIV/AIDS and STD expert, views implant research as promising but emphasizes the importance of adherence. While the implant approach shows great potential, its success in animals does not guarantee success in humans. Additionally, the implant’s replenishment requirement necessitates patient and provider commitment to timely maintenance.


The refillable implant for PrEP delivery holds great promise in the fight against HIV transmission. Animal research has demonstrated the implant’s ability to deliver antiretroviral medication effectively and provide full protection against simian HIV exposure. However, further research and human trials are necessary to validate these findings and assess long-term safety and efficacy. If successful, the implant could revolutionize PrEP administration, offering a more convenient and reliable option for individuals at risk of HIV infection. As researchers continue their efforts to combat HIV, innovative approaches like the refillable implant bring hope for a future free from this devastating disease.


  • Dr. Phillip O.Coffin

    Phillip O. Coffin, M.D., M.I.A., F.A.C.P., is the Director of Substance Use Research at the San Francisco Department of Public Health. He is board-certified in internal medicine, infectious diseases, and addiction medicine; specific foci of Dr. Coffin’s training include general infectious diseases, HIV and viral hepatitis, buprenorphine maintenance, addiction management, and drug poisoning.