Biktarvy and Acute Kidney Injury Risk
Biktarvy (bictegravir, emtricitabine, and tenofovir alafenamide) has a low risk of causing acute kidney injury compared to older tenofovir-containing regimens, but kidney function should still be monitored during treatment, particularly in patients with pre-existing renal impairment.
Kidney Safety Profile of Biktarvy
Biktarvy contains tenofovir alafenamide (TAF), which was specifically developed to reduce the renal toxicity associated with the older tenofovir disoproxil fumarate (TDF) formulation. The FDA label for Biktarvy specifically mentions:
- "New or worse kidney problems, including kidney failure" as a possible side effect 1
- Healthcare providers should "do blood and urine tests to check your kidneys when starting and during treatment with BIKTARVY" 1
- "Your healthcare provider may tell you to stop taking BIKTARVY if you develop new or worse kidney problems" 1
Mechanisms of Potential Renal Toxicity
While Biktarvy has improved renal safety compared to older HIV regimens, there are still potential mechanisms for kidney injury:
- Tenofovir alafenamide can cause proximal tubular dysfunction in rare cases
- Drug interactions may increase the risk of nephrotoxicity
- When combined with other potentially nephrotoxic medications, risk may increase
Risk Factors for Kidney Injury with Biktarvy
Patients at higher risk for developing kidney problems while on Biktarvy include:
- Those with pre-existing chronic kidney disease
- Patients taking other nephrotoxic medications
- Patients with hepatitis coinfection
- Older individuals
- Those with diabetes or hypertension
Drug Interactions Affecting Kidney Risk
The KASL clinical practice guidelines note that when certain antiretrovirals are combined with other medications, renal toxicity risk may increase:
- When rilpivirine or efavirenz is used with tenofovir and ledipasvir/sofosbuvir, "tenofovir levels are increased with ledipasvir/sofosbuvir, which may increase the risk of renal toxicity" 2
- Patients at high risk for renal toxicity (CrCl 30-60 mL/min or pre-existing evidence of Fanconi syndrome) should have renal function monitored every 2-4 weeks when on such combinations 2
Monitoring Recommendations
The KDIGO guidelines recommend:
- "Kidney function must be monitored in patients who are exposed to agents that are associated with kidney injury or dysfunction, to limit the risk and progression of AKI and AKD" 2
- "Patients should receive potentially nephrotoxic medications only if needed and only for as long as needed" 2
Special Populations
For patients with existing kidney disease:
- Biktarvy can be used in patients with creatinine clearance ≥30 mL/min 3
- For patients on dialysis, "take your daily dose of BIKTARVY following dialysis" 1
- Case reports suggest Biktarvy "appears to be an option for individuals with HIV who have ESRD and require long-term HD" 4
Comparison to Other HIV Medications
Tenofovir disoproxil fumarate (TDF), an older formulation of tenofovir, has been more strongly associated with kidney injury:
- The HIV Medicine Association guidelines note that "an increased risk of tenofovir-associated nephrotoxicity was observed in patients with baseline renal insufficiency" 2
- They recommend that TDF "should be discontinued in patients who develop reduced GFR (ie, by >25% from baseline and to a level <60 mL/minute/1.73 m²), particularly when there is evidence of proximal tubular dysfunction" 2
Conclusion
While Biktarvy has a better renal safety profile than older HIV regimens containing TDF, it still carries some risk of kidney injury. Regular monitoring of kidney function is recommended, especially in high-risk patients. The tenofovir alafenamide component in Biktarvy was specifically designed to reduce renal toxicity while maintaining efficacy against HIV.