Abstract Body


Long-acting cabotegravir (CAB-LA) is highly effective as HIV PrEP and superior to daily oral F/TDF in sexually active adults. We report a 28-year-old gender diverse patient assigned male at birth who acquired HIV-1 91 days after transitioning from F/TAF to CAB-LA despite on-time dosing.


Electronic medical records were reviewed to assess patient history and CAB-LA administration details. Plasma 4th generation HIV-1/2 Ag/Ab combination immunoassay and HIV-1 RNA quantitative PCR were performed at each injection visit.


Patient was on daily F/TAF for ten months prior to CAB-LA with acceptable adherence, missing 1 dose per week. Their medical history included hypothyroidism on levothyroxine and unconfirmed hypogonadism with illicit use of IM testosterone cypionate complicated by significantly elevated total testosterone levels. They were sexually active with cisgender men, endorsing condomless oral and anal sex with one primary partner and 20-30 unique partners per month. In the past 6 months, patient was diagnosed with syphilis and mpox. Patient was given 600mg of CAB-LA into their left gluteal medius on Day 0, 27, and 91. Day 0 and 27, plasma HIV 1/2 Ag/Ab was non-reactive and HIV-1 RNA PCR was not detected. Patient reported flu-like illness on Day 76 with positive SARS-COV-2 PCR; they completed a five-day course of nirmatrelvir-ritonavir with rapid resolution of symptoms. At the third injection of 600mg CAB-LA on Day 91, their plasma HIV 1/2 Ag/Ab was non-reactive but the HIV-1 RNA PCR test was detected at 1.48log c/mL. On repeat testing on Day 100, plasma HIV 1/2 Ag/Ab was reactive with HIV-1 Ab detected on differentiation assay and HIV-1 RNA PCR was detected at 1.30 log c/mL. Patient’s primary partner was living with HIV resistant to NRTIs (65R, 118I) and INSTIs (92G) with undetectable plasma HIV-1 RNA for the past 24 months. Patient’s viremia was below the threshold to perform standard HIV-1 sequencing; HIV-1 DNA qualitative PCR and HIV-1 proviral DNA resistance testing are currently pending. Patient ultimately started on F/TAF/DRV/COBI and DTG on Day 112.


This patient’s history suggests HIV-1 infection despite on-time and appropriate CAB-LA injections. To our knowledge, this is the first case of CAB-LA PrEP failure outside the setting of a clinical trial and highlights the diagnostic and management challenges that may arise with such breakthrough infections in the real world.

HIV-1 Breakthrough Infection on CAB-LA Timeline