Renal safety profile of STB in virologically suppressed subjects from two randomized phase 3b switch trials.

ABSTRACT

INTRODUCTION: Cobicistat, a component of stribild (STB), is known to inhibit renal creatinine secretion. A detailed analysis of the renal safety profile of STB in two Phase 3b switch studies of virologically-suppressed individuals on stable therapy STRATEGY(S)-PI (STB vs a RTV-boosted protease inhibitor [PI] with emtricitabine and tenofovir DF [FTC/TDF]); and STRATEGY(S)-NNRTI (STB versus a non-nucleoside reverse transcriptase inhibitor [NNRTI] with FTC/TDF) is herein described. MATERIALS AND METHODS: Baseline eGFR ≥70 mL/min was an inclusion criterion. The renal safety profile of STB was examined by baseline eGFR through week 48 (i.e., changes in eGFR, renal tubular laboratory abnormalities, investigator-reported renal adverse events leading to discontinuation and unreported subclinical proximal renal tubulopathy [PRT]). Subclinical PRT was defined as a confirmed serum-creatinine increase ≥0.4 mg/dL and two or three markers of renal tubular dysfunction (hypophosphatemia, normoglycemic glycosuria, proteinuria) occurring at the same visit at least once and with no alternative etiologies. RESULTS: In S-PI, 433 subjects (STB 293; PI 140) and in S-NNRTI, 434 subjects (STB 291; NNRTI 143) were randomized and treated. Most (>85%) STB subjects had a baseline eGFR ≥90 mL/min. STB subjects with baseline eGFR <90 mL/min had smaller declines in eGFR compared to those with baseline eGFR ≥90 mL/min and similar occurrences of renal tubular laboratory abnormalities (Table 1). Rate of renal adverse events leading to study drug discontinuation were similar for the STB group (one PRT in a subject with baseline tubular laboratory abnormalities consistent with underlying PRT and one isolated increase in serum creatinine) and PI group (one isolated decrease in eGFR); none in the NNRTI group. The case of PRT improved after study drug discontinuation. There were no cases of unreported subclinical PRT in any group. CONCLUSIONS: In this virologically suppressed patient population, the renal safety of STB did not differ by baseline eGFR. The renal discontinuation rate was low in the STB group, similar to the RTV-boosted PI group, and consistent with published historical rates.