What laboratory tests are required prior to initiating lenacapavir (HIV-1 capsid inhibitor) therapy?

Laboratory Tests Required Prior to Lenacapavir Initiation

Prior to initiating lenacapavir therapy, HIV screening must be performed using an antigen/antibody-specific test with confirmation by an RNA-specific assay to rule out undiagnosed HIV infection. 1

Essential Laboratory Tests Before Starting Lenacapavir

HIV Testing Requirements

• HIV screening with an antigen/antibody-specific test
• Confirmation of negative results with an RNA-specific assay, even if results are available after lenacapavir initiation 1
• This testing is critical as drug-resistant HIV-1 variants can develop with lenacapavir use in undiagnosed HIV infection 1

Standard HIV Care Laboratory Tests

While lenacapavir-specific guidelines are emerging, standard pre-antiretroviral therapy tests should include:

1. HIV Disease Assessment

   • CD4 cell count with percentage 2
   • Plasma HIV-1 RNA level (viral load) 2
   • HIV genotypic resistance testing 2

2. Safety Laboratory Tests

   • Complete blood count with differential 2
   • Serum chemistry panel including:
     • Liver function tests (ALT, AST, bilirubin, alkaline phosphatase) 2
     • Renal function tests (electrolytes, BUN, creatinine) 2
     • Calculated creatinine clearance or estimated GFR 2
   • Fasting lipid profile 2
   • Fasting blood glucose 2
   • Urinalysis (protein, glucose, sediment) 2

3. Coinfection Screening

   • Hepatitis B serology (HBsAg, HBsAb, anti-HBc) 2
   • Hepatitis C antibody with reflex HCV RNA if positive 2
   • Tuberculosis screening (TST or IGRA) 2
   • Toxoplasma IgG antibody 2
   • Sexually transmitted infection screening 2

Special Considerations for Lenacapavir

While lenacapavir does not require specific laboratory monitoring beyond standard HIV care tests, clinicians should be aware that:

• No dosage adjustment is needed for patients with mild, moderate, or severe renal impairment (estimated creatinine clearance ≥15 mL/min) 3
• No dosage adjustment is needed for patients with mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment 3
• Lenacapavir has not been studied in patients with end-stage renal disease (CrCl <15 mL/min) or severe hepatic impairment (Child-Pugh Class C) 3

Monitoring After Initiation

After starting lenacapavir:

• HIV RNA should be monitored every 4-6 weeks until virus is undetectable 2
• For subsequent injections of lenacapavir, HIV screening must be repeated prior to each dose 1
• Continued monitoring for treatment resistance is important, particularly if there are concerns about functional monotherapy 4

Pitfalls to Avoid

• Failure to confirm HIV-negative status before initiating therapy could lead to development of drug-resistant HIV variants 1
• Overlooking baseline resistance testing may miss pre-existing resistance patterns
• Not assessing renal and hepatic function could miss contraindications for other antiretrovirals in the regimen
• Missing coinfection screening could lead to undiagnosed comorbidities that affect HIV management