Utility of Cellular Measurements of Non-Specific Endocytosis to Assess the Target-Independent Clearance of Monoclonal Antibodies.

Past studies have demonstrated higher clearance for monoclonal antibodies possessing increased rates of non-specific endocytosis. However, this metric is oftentimes evaluated indirectly using biophysical techniques or cell surface binding studies that may not provide insight into the specific rates of cellular turnover. Furthermore, few examples evaluating non-specific endocytosis have been reported for a therapeutic antibody that reached clinical assessment. In the current report, we evaluated a therapeutic human immunoglobulin G2 monoclonal antibody targeted against the interleukin-4 receptor alpha chain (IL-4Rα) that exhibited elevated target independent clearance in previous Phase 1 and 2 studies. We confirmed high non-specific clearance of the anti-IL-4Rα antibody as compared to a reference antibody during pharmacokinetic assessments in wild type mice where target-mediated disposition was absent. We then developed a cell-based method capable of measuring cellular protein endocytosis and demonstrated the anti-IL-4Rα antibody exhibited marked non-specific uptake relative to the reference compound. Antibody homology modeling identified the anti-IL-4Rα antibody possessed positive charge patches whose removal via targeted mutations substantially reduced its non-specific endocytosis. We then expanded the scope of the study by evaluating panels of both preclinical and clinically relevant monoclonal antibodies and demonstrate those with the highest rates of non-specific uptake in vitro exhibited elevated target independent clearance, low subcutaneous bioavailability, or both. Our results support the observation that high non-specific endocytosis is a negative attribute in monoclonal antibody development and demonstrate the utility of a generic cell-based screen as a quantitative tool to measure non-specific endocytosis of protein therapeutics at the single-cell level.

Cryptococcal Infection of the Ventriculoperitoneal Shunt in an HIV-Infected Patient with an Excellent Immunovirologic Status.

BACKGROUND: Cryptococcus spp. is a rare cause of ventriculoperitoneal shunt (VPS) infection, with a variable clinical presentation. Diagnosis and treatment of this entity are challenging. CASE DESCRIPTION: A cryptococcal VPS infection occurred in a human immunodeficiency virus-infected patient with an excellent immunovirologic status, with an abdominal mass as the only clinical sign at presentation. Microbiologic diagnosis was confirmed when Cryptococcus neoformans was isolated in 4 cerebrospinal fluid samples on different days. The patient was treated with dual antifungal therapy (liposomal amphotericin B plus flucytosine). The VPS was initially externalized and then removed. At 12-month follow-up, the patient remained asymptomatic, and no replacement VPS was required. CONCLUSIONS: This is the first reported case of cryptococcal VPS infection in a patient with human immunodeficiency virus infection. Clinical outcome was excellent after dual antifungal therapy plus device withdrawal. Diagnosis and treatment of this entity remain a challenge for clinicians.