CCR5 Receptor Occupancy Analysis Reveals Increased Peripheral Blood CCR5+CD4+ T Cells Following Treatment With the Anti-CCR5 Antibody Leronlimab

Abstract

CCR5 plays a central role in infectious disease, host defense, and cancer progression, thereby making it an ideal target for therapeutic development. Notably, CCR5 is the major HIV entry co-receptor, where its surface density correlates with HIV plasma viremia. The level of CCR5 receptor occupancy (RO) achieved by a CCR5-targeting therapeutic is therefore a critical predictor of its efficacy. However, current methods to measure CCR5 RO lack sensitivity, resulting in high background and overcalculation. Here, we report on two independent, flow cytometric methods of calculating CCR5 RO using the anti-CCR5 antibody, Leronlimab. We show that both methods led to comparable CCR5 RO values, with low background on untreated CCR5+CD4+ T cells and sensitive measurements of occupancy on both blood and tissue-resident CD4+ T cells that correlated longitudinally with plasma concentrations in Leronlimab-treated macaques. Using these assays, we found that Leronlimab stabilized cell surface CCR5, leading to an increase in the levels of circulating and tissue-resident CCR5+CD4+ T cells in vivo in Leronlimab-treated macaques. Weekly Leronlimab treatment in a chronically SIV-infected macaque led to increased CCR5+CD4+ T cells levels and fully suppressed plasma viremia, both concomitant with full CCR5 RO on peripheral blood CD4+ T cells, demonstrating that CCR5+CD4+ T cells were protected from viral replication by Leronlimab binding. Finally, we extended these results to Leronlimab-treated humans and found that weekly 700 mg Leronlimab led to complete CCR5 RO on peripheral blood CD4+ T cells and a statistically significant increase in CCR5+CD4+ T cells in peripheral blood. Collectively, these results establish two RO calculation methods for longitudinal monitoring of anti-CCR5 therapeutic antibody blockade efficacy in both macaques and humans, demonstrate that CCR5+CD4+ T cell levels temporarily increase with Leronlimab treatment, and facilitate future detailed investigations into the immunological impacts of CCR5 inhibition in multiple pathophysiological processes.

Suppression of human and simian immunodeficiency virus replication with the CCR5-specific antibody Leronlimab in two species

“…To this end, we found that both cohorts had comparable mean (± SD) plasma concentrations of 48.6 (± 5.4) and 46.1 (± 27.0) μg/mL for cohort 1 and 2, respectively, likely due to the prolonged treatment period ( Fig 2B ). To quantify the saturation of cell surface CCR5 receptors by Leronlimab, we developed two complementary methods to measure free or Leronlimab-bound CCR5 receptors via flow cytometry ( S4 Fig ), which were used interchangeably to calculate for the percentage of CCR5 receptor occupancy (RO) by Leronlimab [ 17 ]. In all five participants, we observed near-complete CCR5 RO by Leronlimab on CD4+ T-cells, CD8+ T-cells, and CD14+ monocytes in the blood ( Fig 2C ).…”

Reduced Cell Surface Levels of C-C Chemokine Receptor 5 and Immunosuppression in Long Coronavirus Disease 2019 Syndrome

“…With genetic polymorphisms reducing cell surface CCR5 levels conferring increased risk of severe COVID-19 [ 4 ], this suggests a complex role for CCR5 in balancing inflammatory and antiinflammatory effects, for example, through T regulatory cells. While leronlimab reduces the signaling of CCR5 by Regulated upon Activation, Normal T Cell Expressed and Presumably Secreted (RANTES) [ 11 ], emerging data show that leronlimab stabilizes CCR5 expression, presumably through direct binding [ 12 , 13 ], which may either change the signaling or activity of other ligands, such as Monocyte Inflammatory Protein (MIP)-1ɑ, MIP-1β, and/or Monocyte Chemoattractant Protein (MCP-2), or increase the expression of other CCRs through heterodimerization [ 14 ]. While this is a small exploratory pilot study with potential confounders, our results support further research into the role of CCR5 in long COVID.…”

A Predictive Model for Identifying the Most Effective Anti-CCR5 Monoclonal Antibody

“…Monoclonal antibodies (mAbs) that act as antagonists of CCR5 have been increasingly examined [7] and have led to many potential therapeutic solutions [3,[8][9][10][11][12][13][14][15][16][17][18][19][20]. However, currently, there is information lacking about the structural interaction between mAbs and CCR5 [21].…”