CONFERENCE UPDATE: CROI 2025

Zero HIV acquisition and high persistence with CAB LA as PrEP: 12-month results from the PILLAR trial

INFECTIOUS DISEASE
01 Jun 2025

STUDY DESIGN

In 2022, men who have sex with men (MSM) and transgender men (TGM) accounted for 67% and <1% of new HIV diagnoses in the United States, respectively.1 Additionally, an estimated 15% of MSM and 3% of TGM were living with HIV.1 Long-acting cabotegravir (CAB LA), administered every two months via intramuscular injection, is the first and only approved long-acting medication for human immunodeficiency virus 1 (HIV-1) pre-exposure prophylaxis (PrEP) in adults and adolescents.1 It has demonstrated superiority to daily oral PrEP (tenofovir disoproxil fumarate + emtricitabine) in preventing new HIV acquisition.1 CAB LA has consistently shown high effectiveness and tolerability across both clinical trials and real-world implementation studies.1

The PILLAR trial evaluates the real-world adoption and clinical outcomes of CAB LA, with this analysis presenting 12-month findings on HIV incidence, persistence, and safety.1 The PILLAR trial is a phase 4, real-world, implementation science study designed to assess CAB LA integration into clinical practice.1 In this site-randomized study, 17 sites were assigned to either dynamic CAB LA implementation (n=11) or routine CAB LA implementation (n=6).1 A total of 201 participants were enrolled and initiated CAB LA, with a median age of 35 years (interquartile range [IQR]: 29-44); 6% were TGM, 26% were Black, and 38% were Hispanic.1 Notably, 22% had not used oral PrEP in the six months prior to CAB LA initiation.1 Participants were eligible to initiate CAB LA through either a direct-to-inject approach or an oral lead-in phase, followed by every-2-month (Q2M) CAB LA injections.1 Over a 12-month follow-up period, the study assessed key endpoints including HIV incidence, HIV testing, persistence (continuation of CAB LA use), safety and tolerability.1

FINDINGS

Key endpoints:

  • Key endpoints assessed included HIV incidence, HIV testing, and persistent use of CAB LA1

  • There were no reported cases of HIV acquisition through month 121

  • At month 6 and month 12, persistence on CAB LA was 85% (n=171/201) and 73% (n=146/201)1

  • In the real world, 53% of study sites used HIV antigen/antibody testing, while 47% used HIV ribonucleic acid (RNA) testing as their primary method. No site routinely used both tests for the majority of participants1

  • Clinics serving participants with prior PrEP use primarily used HIV antigen/antibody testing (57%), whereas those serving participants without prior PrEP use were more varied, with 50% using antigen/antibody tests, 38% using HIV RNA tests, and 13% using both1

  • 13% of participants (MSM, n=26; TGM, n=1) acquired a sexually transmitted infection that was identified through last on-study visit (gonorrhea, n=14; chlamydia, n=12; syphilis, n=7)1

  • Overall, 70% (n=141/201) of participants completed all injections within the study. Five (2%) participants missed an injection and received oral CAB (n=1) or alternative PrEP (n=4)1
Safety:

  • A total of 11 (5%) participants had AEs leading to discontinuation, most commonly due to injection site pain (n=6)1

  • Adverse events (AEs) related to CAB LA were rare, with injection site pain the most frequently reported (3%, n=6), followed by fatigue (1%, n=2)1

 

"Zero cases of HIV acquisition were found through month 12, supporting the robust and sustained effectiveness of CAB LA in the real-world setting

Dr. Taimur Khan

Fenway Health, Boston,

United States

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