The primary objective of the Second-line Switch to DTG (2SD) study is to evaluate the non-inferiority of switching to a DTG containing regimen relative to maintaining a PI/r containing regimen among treatment-experienced, INSTI-naïve, virologically suppressed HIV-1 positive adults (≥18 years old) as determined by the proportion of participants having HIV-1 RNA ≥ 50 copies/ml at 48 weeks after enrollment.

Kenya has the fourth largest burden of HIV globally with close to 1.2 million people living with HIV, ⁹ the majority of whom receive HIV treatment from public outpatient clinics. The Kenya National ARV Guidelines do not recommend performing DRT for patients failing an NNRTI-based first line regimen before switching to a PI/r-based second-line regimen, ³ so resistance profiles are not available for most patients currently on PI/r-based ART.

The 2SD study takes place at four public hospitals in Kenya: Kenyatta National Hospital (KNH), Thika Level 5 Hospital, Kiambu Referral Hospital, and Jaramogi Oginga Odinga Teaching and Referral Hospital (JOOTRH). The four study sites currently provide ART to approximately 1,500 virally suppressed adults on PI/r-based second-line regimens.

2SD is an open-label, randomized, active-controlled, multi-centre non-inferiority trial. The trial enrolled participants from among people receiving outpatient HIV care at the four study sites in Kenya. Inclusion criteria were HIV-1 positive adults (≥18 years); on a second-line regimen of PI/r plus two NRTIs for at least 24 weeks; a treatment history of failing a prior NNRTI-containing ART regimen; and virally suppressed (plasma HIV-1 RNA < 50 copies/mL) for at least 12 weeks prior to enrollment. Women of childbearing potential (WOCBP) were not pregnant at the time of screening or enrollment and agreed to use effective contraception throughout the study period. Exclusion criteria included: any prior INSTI exposure; current use of disallowed concomitant therapy; aspartate aminotransferase (AST) or alanine aminotransferase (ALT) at least five times the upper limit of normal in conjunction with hepatitis B virus (HBV) or hepatitis C virus infection; an estimated glomerular filtration rate of 50 ml/min or below in conjunction with HBV infection; advanced renal disease requiring dialysis; currently pregnant or breastfeeding; documented opportunistic infection within four weeks prior to enrollment; investigator opinion that the patient should switch from PI/r to DTG immediately for clinical reasons; or any condition or laboratory result which in the investigator’s opinion would interfere with assessments or completion of the study.

Based on a recommendation from the first Data and Safety Monitoring Board (DSMB) approximately four months after enrollment began and after 67% of participants were enrolled, the study protocol was amended to exclude new participants with baseline grade 3 or 4 lipid abnormalities as this would warrant a switch off of their PI/r immediately.

Screening investigations included HIV-1 RNA viral load, serum creatinine, ALT, AST, hepatitis B surface antigen (HBsAg) and urine pregnancy test for WOCBP. After the DSMB recommended the exclusion of patients with grade 3 or 4 lipid abnormalities, fasting lipids and fasting serum glucose were conducted as screening rather than baseline investigations.

Eligible participants were enrolled into the study within 28 days from their screening visit.

Participants were randomized in a 1:1 ratio using a computer-generated randomization sequence to either continue their pre-enrollment PI/r-based regimen or switch from PI/r to DTG. The study coordinator was blinded to participant details at the time of randomization; he was only provided with the participant identifier after all enrollment criteria were met and then generated the randomization number and study arm allocation. The randomization number and study arm allocation were provided to the site investigators who enrolled the participants. This is an open label trial and neither investigators nor participants were masked to treatment assignment.

Participants were randomized to continue their pre-enrollment PI/r (ATV/r, LPV/r or DRV/r) or switch from PI/r to DTG, while continuing the NRTIs from their pre-enrolment regimen. Changes to the NRTIs were allowed throughout the study period only for clinical indications following the Kenya National ARV Guidelines. ³

For patients randomized to switch to DTG, the DTG was administered as a once-daily dosage without regard to meals, either as a single 50 mg tablet with a separate tablet of co-formulated AZT/3TC (300 mg/150 mg) one tablet twice daily, or as a single co-formulated tablet of DTG/3TC/TDF (50 mg/300 mg/300 mg) once daily, or as a single co-formulated tablet of DTG/3TC/ABC (50 mg/300 mg/600 mg) once daily. For patients randomized to remain on their pre-enrollment PI/r, the PI/r was administered as co-formulated LPV/r (200 mg/50 mg) two capsules twice daily, or co-formulated ATV/r (300 mg/100 mg) one tablet once daily. DRV/r is generally reserved for patients with prior PI/r failure in Kenya and no study participants were on DRV/r at enrollment. PI/r were recommended to be taken with food. For patients on PI/r, the NRTIs were administered as additional tablets of co-formulated AZT/3TC (300 mg/150 mg) one tablet twice daily, or co-formulated TDF/3TC (300 mg/300 mg) one tablet once daily, or ABC/3TC (600 mg/300 mg) one tablet once daily.

Study visits were scheduled at enrollment and weeks 4, 12, 24, 36 and 48. Visits were allowed to take place within ± 7 days from the specified follow-up date. Plasma HIV-1 RNA was measured at screening and weeks 4, 12, 24 and 48. Other investigations at screening, enrollment or follow-up included CD4 count, fasting lipid profile (total cholesterol, LDL and HDL cholesterol, ratio of total cholesterol to HDL cholesterol, and triglycerides), fasting serum glucose, serum creatinine, AST, ALT, HBsAg and complete blood count. For patients with protocol defined virological failure (PDVF), consisting of two consecutive HIV-1 RNA viral load results of 50 copies/ml or greater separated by at least two weeks, if their confirmatory viral load was 500 copies/ml or greater then genotypic drug resistance testing of integrase, protease and reverse transcriptase was attempted. All laboratory investigations were performed at accredited laboratories, at either the University of Nairobi Molecular and Infectious Diseases Research Laboratory or Lancet Laboratories. Point-of-care urine pregnancy testing was performed at all study visits for WOCBP.

Clinical screening for tuberculosis (TB) was performed at every visit following the Kenya National ARV Guidelines. ³ Adverse events were graded using standard criteria. ¹⁰ The HIV Treatment Satisfaction Questionnaire Status version (HIVTSQs) was administered at enrollment and week 48, and the HIVTSQ Change version (HIVTSQ _c) was administered at week 24. Treatment adherence was evaluated using pill counts of unused study drug at weeks 4, 12, 24, 36 and 48.

Study treatment was discontinued if requested by the participant, substitution of the DTG or PI/r was required due to drug-drug interactions or unacceptable toxicity, participant failure to comply with protocol requirements, pregnancy, or if deemed in the best interested of the participant for clinical reasons.

The primary outcome is the proportion of participants with plasma HIV-1 RNA of 50 copies/ml or greater at week 48 by the US Food and Drug Administration (FDA) snapshot algorithm. Secondary outcomes include proportion of participants with plasma HIV-1 RNA of 50 copies/ml or greater at week 24, proportion of participants able to maintain virological suppression with HIV RNA less than 50 copies/ml at weeks 24 and 48, change in CD4 count from baseline to weeks 24 and 48, and patient satisfaction as measured by the HIVTSQ at weeks 24 and 48.

Safety outcomes include clinical and laboratory adverse events at weeks 24 and 48, change in fasting blood glucose from baseline to weeks 24 and 48, change in fasting lipid parameters from baseline to weeks 24 and 48, and genotypic resistance to the study drug.

The sample size was calculated based on the primary endpoint of HIV-1 RNA of 50 copies/ml or greater at week 48 using the FDA snapshot method for the Intention-to-Treat Exposed (ITT-E) population. The ITT-E population is defined as all randomized participants who receive at least one dose of study drug, analyzed according to their randomization assignment. The sample size calculation assumed that the true difference in efficacy between treatment arms would be zero and that the overall virological failure rate would be 3% at week 48. A total of 766 participants (383 participants per study arm) were required to provide at least 90% power to demonstrate non-inferiority for the DTG arm, compared to the control arm, with a one-sided significance level of 2.5% and non-inferiority margin of 4%. The sample size was increased to 794 after the DSMB recommended excluding new participants with baseline grade 3 or 4 lipid abnormalities, to allow for fully powered sensitivity analysis if we excluded those who were already enrolled with grade 3 or 4 lipid abnormalities by the time of the DSMB recommendation.

For presentation of baseline results in this manuscript, participant demographic data and baseline characteristics using the ITT-E population were summarized by treatment group using descriptive statistics. Baseline continuous variables were summarized using medians (interquartile ranges), while categorical variables were summarized using counts and percentages. Ranksum tests were used for bivariate analysis between the DTG and PI/r groups on continuous variables while Chi-square or Fisher’s exact test as suitable were used for categorical variables, reporting the p values. All statistical tests were evaluated for significance at the 5% level.

Statistical methods planned for interim and final analysis include evaluation of efficacy, safety and patient satisfaction. The primary analysis will be performed after all enrolled participants complete their week 48 study visit or prematurely discontinue the study drug. Analysis of the primary endpoint will be performed for the ITT-E population using the FDA snapshot method. Non-inferiority for the primary endpoint will be established if the upper bound of the 95% confidence interval for the difference in proportion of participants with plasma HIV-1 RNA of 50 copies/ml or greater between groups is less than 4% in the ITT-E population. The primary endpoint will also be analyzed with the per-protocol (PP) population.

A secondary analysis will be performed for treatment success, defined as having HIV-1 RNA less than 50 copies/ml at week 48 in the ITT-E and PP populations, using the FDA snapshot method. Non-response is defined as any of the following: PDVF, death from any cause, loss to follow-up, consent withdrawal, or permanent change or interruption of the randomized treatment. Non-inferiority for the treatment success analysis will be demonstrated if the lower bound of the 95% CI of the difference between the groups is greater than –10%.

Other planned analysis include change in median CD4 count, lipid parameters, fasting glucose, and anthropometric measurements from baseline to weeks 24 and 48.

Safety analysis will be performed. Any AEs, grade 3 and 4 AEs, treatment-related AEs (all grade), treatment-modifying AEs (all grade), deaths, SAEs, and AEs occurring in at least 5% of participants will be described and compared by group.

Stata version 15.1 and R version 3.6.4 will be used to perform calculations and analyses.

An international DSMB is monitoring the main safety and efficacy outcome measures and overall conduct of the trial, and an independent study monitor conducted site initiation visits and will continue to monitor the study to conclusion.

The study was approved by the joint ERC of KNH and University of Nairobi and by the ERC of JOOTRH. All participants provided written informed consent. This clinical trial is registered at clinicaltrials.gov, NCT04229290.