A 38-year-old woman started antiretroviral therapy (ART) in 2007 with zidovudine (AZT), lamivudine (3TC) and efavirenz. Her baseline human immunodeficiency virus (HIV) viral load and cluster of differentiation 4 (CD4) cell count results were not available. In September 2009, she experienced virological failure (this HIV viral load result is not available), and a genotypic antiretroviral resistance test showed a thymidine analogue mutation (TAM, K219KE [i.e. mixed population of mutant and wild type at that codon]), M184M/V and three non-nucleoside reverse transcriptase inhibitor (NNRTI) mutations (A98G, E138A and K238T) (see Table 1).
Based on this genotype, her regimen was changed to tenofovir (TDF), emtricitabine (FTC) and ritonavir-boosted atazanavir. She then transitioned from HIV care in the private sector to the public sector where she was changed to abacavir (ABC), 3TC and ritonavir-boosted lopinavir. When she returned to private sector care in May 2017, she reported severe diarrhoea, resulting in poor adherence to ART. Her medication was switched to ABC, 3TC and ritonavir-boosted atazanavir and the diarrhoea settled.
In June 2017, she was diagnosed with tuberculosis (TB) and was started on a rifampicin-based TB treatment. Her HIV viral load at this time was 345 406 copies/mL. As she already had significant diarrhoea on standard dose ritonavir-boosted lopinavir, it was felt that double-dose ritonavir-boosted lopinavir during TB treatment would not be tolerated. Given that AZT was still fully susceptible at the time of first-line failure, it was thought that AZT would still be susceptible and therefore providing one active nucleoside reverse transcriptase inhibitor (NRTI) to accompany dolutegravir (DTG). The patient was therefore switched to AZT, 3TC and DTG 50 mg 12-hourly. The patient informed her doctor in July 2017 that she was experiencing insomnia on this regimen. She was reassured and advised to continue until she had completed TB treatment.
There were regular pharmacy claims for treatment from June 2017 until November 2017 when her viral load was 2800 copies/mL. A resistance test was performed in February 2018, and the following mutations were observed: three integrase mutations (T66TI, G118R and E138EK) resulting in high-level resistance to raltegravir and elvitegravir and intermediate resistance to DTG (based on the Stanford score), M184V and two NNRTI mutations (A98G and E138A). A sample was also collected for phenotypic testing at monogram and the results showed that there was a 21-fold reduction in DTG susceptibility. Furthermore, all the other available integrase inhibitors had reduced susceptibility (3.92; 32- and 24-fold reduction to bictegravir, elvitegravir and raltegravir, respectively).
She then admitted to only taking DTG 50 mg in the morning because she had experienced insomnia with twice daily dosing, which resolved if she skipped the evening dose. Based on the resistance test result, her ART regimen was changed to TDF, FTC and ritonavir-boosted atazanavir in February 2018 with rifabutin replacing rifampicin for the remaining months of TB treatment. An HIV viral load performed 3 months after the change was 230 copies/mL, and subsequent viral loads have been below 20 copies/mL for about 12 months.