Case report We present the case of a 42 yr old female, diagnosed with HIV in 1992, presenting on a failing PI and integrase inhibitor based antiretroviral (ARV) regimen. She was intolerant to ritonavir, had significant drug resistance and poor adherence, but achieved virological suppression using the novel combination of Stribild™ [elvitegravir (EVG)/cobicistat/tenofovir (TDF)/emtricitabine (FTC)] and darunavir (DRV). She had been on multiple ARV combinations since 1994, including NRTI mono-therapy. Medication intolerance, non-adherence and stopping ARVs against advice, had led to HIV drug resistance. Her regimen comprised raltegravir (RAL), DRV, RTV and TDF. Due to her intolerance to RTV, she took this sporadically. This resulted in viral rebound from <40 c/ml to 5,483 c/ml. Cumulative resistance assays demonstrated NRTI, NNRTI and protease inhibitor mutations. Her virus was X4 tropic, but remained sensitive to integrase inhibitors.

To combat this issue a novel approach using Stribild™ with DRV 1200 mg OD was started, taking into account the patient’s resistance profile and RTV intolerance. Due to minimal pharmacokinetic (PK) studies of this combination, and the potential for suboptimal and/or altered PK of cobisistat, EVG and DRV, therapeutic drug monitoring was utilised. Adherence was monitored using MEMs CAP™, which showed excellent adherence. Trough drug concentrations at 23 hrs post-dose were 2692 ng/ml for DRV and 1,155 ng/ml for EVG. Subsequently, she achieved rapid virological suppression, asymptomatically.

Discussion/conclusion Issues of drug intolerance and resistance can be a therapeutic dilemma. We present the first case study using the regimen of Stribild™/DRV, utilising cobi to enhance DRV concentrations. This well tolerated salvage regimen may be an option for some individuals.