Long-Acting Cabotegravir for HIV Prevention: Injectable Pre-Exposure Prophylaxis

1. Introduction: Injectable Pre-Exposure Prophylaxis

Cabotegravir is an integrase strand transfer inhibitor (INSTI) that was reformulated as a long-acting injectable suspension, making it possible to protect against HIV acquisition with an intramuscular injection every two months rather than a daily pill. In December 2021 the U.S. Food and Drug Administration approved long-acting cabotegravir for pre-exposure prophylaxis (PrEP) under the brand name Apretude — the first injectable PrEP product. Its clinical importance rests on two large randomized trials, HPTN 083 and HPTN 084, in which it outperformed daily oral tenofovir disoproxil fumarate/emtricitabine (TDF/FTC).

Cabotegravir is unusual in that a single molecule is used both for prevention (as Apretude, alone) and, in combination with long-acting rilpivirine, for treatment (as Cabenuva). This article covers its pharmacology and dosing, the central prevention trials, the regulatory decision, its advantages and drawbacks, the risk of resistance, its role in treatment, and the implementation questions that remain. A clear distinction is maintained between trial-confirmed facts, established approvals, and open questions.

2. Cabotegravir: Pharmacology and Injectable Nanosuspension

Cabotegravir blocks the strand-transfer step of integration, preventing the viral DNA from being covalently inserted into the host chromosome. As a second-generation INSTI it has a higher genetic barrier to resistance than raltegravir and elvitegravir, and it is active at low concentrations. Like dolutegravir and bictegravir, it is an effective anchor drug; unlike them it can also be given as an oral tablet.

The key to cabotegravir’s long-acting behavior is its formulation, not the molecule alone. The injectable product is an aqueous crystalline nanosuspension of a poorly water-soluble form of the drug. After intramuscular injection into muscle, the drug dissolves slowly from the depot, producing plasma concentrations that persist for weeks to months. This pharmacokinetic trick — a depot of slowly dissolving nanocrystals — is what allows an eight-week dosing interval. An oral tablet (30 mg) is available as an optional lead-in to assess tolerability and to confirm that plasma levels are adequate before the first injection.

3. Dosing

For PrEP, the approved schedule is a loading phase of 600 mg intramuscularly, given one month apart for the first two injections, followed by 600 mg every two months (eight weeks) thereafter. The oral lead-in is optional under current labeling; where used it is taken once daily for about four weeks before the first injection. Because drug concentrations decline slowly after the last injection — the so-called pharmacokinetic «tail» — the interval between doses matters: delayed injections can leave levels below the protective threshold, and individuals who discontinue must be counseled and monitored, particularly regarding the possibility of infection during the tail. Missing scheduled injection visits is the principal practical failure mode for this method.

• Loading: 600 mg IM, then a second 600 mg IM one month later.
• Maintenance: 600 mg IM every 8 weeks.
• Oral lead-in (optional): 30 mg once daily for approximately 4 weeks before the first injection.

4. HPTN 083: Men Who Have Sex With Men and Transgender Women

HPTN 083 compared long-acting injectable cabotegravir with daily oral TDF/FTC in cisgender men who have sex with men and in transgender women who have sex with men. The trial was stopped early by its data safety monitoring board because cabotegravir demonstrated clear superiority. The primary analysis reported an incidence rate ratio of approximately 0.34, corresponding to roughly a 66% lower HIV incidence with cabotegravir; the result is commonly summarized as an approximately two-thirds, or roughly 69%, reduction. A small number of infections occurred in the cabotegravir arm, and some of these were associated with integrase resistance mutations, a finding that shapes how the product is monitored and used (Landovitz et al., New England Journal of Medicine, 2021). [Citation details to be verified.]

The trial enrolled a substantial number of transgender women, an important methodological strength given their underrepresentation in earlier prevention research. The comparison of a long-acting injectable against a daily oral pill also means the result partly reflects the real-world difficulty of daily adherence to oral PrEP.

5. HPTN 084: Cisgender Women

HPTN 084 compared long-acting cabotegravir with daily oral TDF/FTC in cisgender women in sub-Saharan Africa — a population in which earlier oral PrEP trials had struggled because of low adherence. This trial was also stopped early for superiority. Cabotegravir reduced HIV incidence by approximately 88% relative to daily oral TDF/FTC, one of the largest effect sizes reported for any HIV prevention intervention (Delany-Moretlwe et al., New England Journal of Medicine, 2022). [Citation details to be verified.]

Together, HPTN 083 and HPTN 084 established long-acting cabotegravir as the most effective biomedical prevention option tested to date in its respective populations, while also reinforcing the observation that much of the advantage over oral PrEP reflects the difficulty of sustaining daily pill use.

6. Regulatory Approval

The FDA approved long-acting cabotegravir for PrEP in December 2021 (Apretude), making it the first injectable PrEP option. The approved indication is for adults and adolescents at risk of sexually acquired HIV who weigh at least a specified threshold, with a negative HIV test required before initiation and before each injection. Because the drug is not active against established HIV infection and could promote resistance if given to a person who is already infected, HIV testing at every visit is a mandatory part of the label. Regulatory decisions in other jurisdictions followed or were under review. These are established regulatory facts. [Marked for verification.]

7. Advantages and Disadvantages

• Advantages: No daily pill; protection does not depend on daily adherence; a dosing interval of two months; high measured efficacy; and a discrete option for people who find daily oral PrEP difficult or stigmatizing.
• Disadvantages: Requires clinic visits for injection; injection-site reactions are common and can be bothersome (pain, swelling, nodules); a mandatory HIV test before each dose; the need to manage the pharmacokinetic tail after discontinuation; and higher cost than generic oral TDF/FTC.
• Practical constraints: The method only works if the person returns for injections on schedule. Programs must therefore build reliable recall and retention systems, because a missed injection creates a window of waning protection.

Injection-site reactions were the most frequent adverse events in the trials; most were mild to moderate and did not lead to discontinuation, but they are a real consideration for acceptability. [Marked for verification.]

8. Resistance Risk and Infection During Waning Drug Levels

The principal biological risk of long-acting INSTI-based PrEP is that a person who becomes infected — for example, after a missed injection while drug levels are declining during the tail — may develop integrase resistance. In HPTN 083, infections in the cabotegravir arm included cases with INSTI resistance mutations. This is why the label requires HIV testing before each dose and why clinical guidance emphasizes prompt management of treatment interruptions. The resistance concern is not hypothetical: it has been observed, and it has implications both for the individual (limiting future treatment options) and for public health (transmission of INSTI-resistant virus). It remains an area of active monitoring. [Citation details to be verified.]

9. Cabotegravir plus Rilpivirine as Long-Acting Treatment

The same long-acting cabotegravir formulation, paired with long-acting rilpivirine, provides a complete injectable treatment regimen under the brand name Cabenuva. Three randomized trials established its role. ATLAS and FLAIR showed that monthly cabotegravir plus rilpivirine injections maintained viral suppression non-inferiorly to daily oral antiretroviral therapy in people who were already suppressed and had no relevant resistance (Swindells et al., 2020; Orkin et al., 2020, New England Journal of Medicine). ATLAS-2M then demonstrated that an every-two-month schedule was non-inferior to monthly dosing (Overton et al., New England Journal of Medicine, 2021).

Long-acting treatment is not appropriate for everyone. It requires a suppressed viral load, absence of resistance to the component drugs, and reliable attendance at injection visits. Virologic failure with resistance to integrase inhibitors or NNRTIs during injectable therapy has been reported and is a recognized risk. [Citation details to be verified.]

10. Implementation, Cost, and Access

Two barriers dominate real-world uptake of long-acting cabotegravir. The first is cost: in the United States the list price of injectable PrEP has been on the order of tens of thousands of dollars per year, far above generic oral TDF/FTC. The second is infrastructure: delivery requires cold-chain-compatible storage, trained staff who can administer intramuscular injections, and a system to call patients back every two months. In high-income settings these are manageable; in resource-limited settings they are substantial. Whether generic manufacture, voluntary licensing, or donor-supported procurement can bring injectable PrEP to the populations that need it most is a major open question. [Marked for verification.]

Implementation research is also examining whether cabotegravir should be offered preferentially to people for whom oral PrEP has failed or is impractical, how to manage transitions between oral and injectable methods, and how to support people who stop injections. These are implementation questions rather than settled evidence.

11. Open Questions

• Long-term rare events. The trials were sufficiently large to establish efficacy, but long-term safety, including rare events and safety in pregnancy, continues to be monitored.
• Discontinuation and the tail. The optimal approach to monitoring and short-course oral bridging after stopping injections is still being defined.
• Comparative positioning. How cabotegravir should rank relative to oral PrEP and the dapivirine ring in different populations is a programmatic decision, not a settled scientific one.
• Resistance surveillance. The frequency and transmission dynamics of INSTI-resistant infection arising during long-acting PrEP require ongoing surveillance.
• Equity. Whether the product reaches the people at highest risk, rather than only those with resources and access, is a central policy question.

12. Conclusion

Long-acting injectable cabotegravir is the most effective biomedical HIV prevention intervention demonstrated in randomized trials to date. In HPTN 083 it reduced HIV incidence by roughly two-thirds relative to daily oral TDF/FTC in men who have sex with men and transgender women, and in HPTN 084 by approximately 88% in cisgender women. It was approved for PrEP in December 2021, the first injectable option, with an eight-week maintenance schedule after a loading phase. Its promise is freedom from daily pill-taking; its costs are injection-site reactions, the need for regular clinical visits and HIV testing, the risk of resistance if infection occurs during waning drug levels, and high price. As a treatment, cabotegravir plus rilpivirine offers a complete long-acting regimen for selected, suppressed patients. Injectable PrEP changes the prevention field, but its public-health impact will depend on affordability, delivery capacity, and retention.

Sources and Key Research Centers

1. National Institute of Allergy and Infectious Diseases (NIAID), NIH — primary funder of the HIV Prevention Trials Network (HPTN), which conducted HPTN 083 and HPTN 084.
2. HIV Prevention Trials Network (HPTN) — trial network responsible for the central cabotegravir prevention studies.
3. U.S. Food and Drug Administration (FDA) — approval of cabotegravir for PrEP (Apretude, December 2021) and of cabotegravir plus rilpivirine (Cabenuva, January 2021).
4. U.S. Centers for Disease Control and Prevention (CDC) — clinical guidance on injectable PrEP and HIV testing requirements.
5. World Health Organization (WHO) — global prevention guidance and considerations for long-acting prevention options.
6. AVAC (Global Advocacy for HIV Prevention) — tracking of injectable PrEP rollout, pricing, and access.
7. Key publications
   • Landovitz RJ, Donnell D, Clement ME, et al. «Cabotegravir for HIV prevention in cisgender men and transgender women.» New England Journal of Medicine, 2021; 385(7): 595-608 (HPTN 083). [Citation details to be verified.]
   • Delany-Moretlwe S, Hughes JP, Bock P, et al. «Cabotegravir for the prevention of HIV-1 in women.» New England Journal of Medicine, 2022; 386(18): 1713-1723 (HPTN 084). [Citation details to be verified.]
   • Swindells S, Andrade-Villanueva JF, Richmond GJ, et al. «Long-acting cabotegravir and rilpivirine for maintenance of HIV-1 suppression.» New England Journal of Medicine, 2020; 382(12): 1112-1123 (ATLAS). [Citation details to be verified.]
   • Orkin C, Arasteh K, Górgolas Hernández-Mora M, et al. «Long-acting cabotegravir and rilpivirine after oral induction for HIV-1 infection.» New England Journal of Medicine, 2020; 382(12): 1124-1135 (FLAIR). [Citation details to be verified.]
   • Overton ET, Richmond G, Rizzardini G, et al. «Long-acting cabotegravir and rilpivirine dosed every 2 months in adults with HIV-1 infection.» New England Journal of Medicine, 2021; 385(1): 58-70 (ATLAS-2M). [Citation details to be verified.]
8. ClinicalTrials.gov — registry records for HPTN 083, HPTN 084, ATLAS, FLAIR, and ATLAS-2M.
9. New England Journal of Medicine — primary venue for the cabotegravir prevention and treatment trials.

Note: percentage reductions are rounded from primary reports; the HPTN 083 effect is reported variously as approximately 66-69% depending on the analysis. Readers should confirm bibliographic details and confidence intervals against the publisher’s record. This article is an editorial scientific overview and is not a medical recommendation.