P0068APABETALONE, A CLINICAL STAGE BET INHIBITOR, REDUCES THE PRO-INFLAMMATORY RESPONSE IN PBMCS FROM FABRY DISEASE PATIENTS ON ERT THERAPY
Authors: Fu Li , Wasiak Sylwia , Rakai Brooke , Stotz Stephanie , Wong Norman , Johansson Jan , Sweeney Michael , Mohan Connie , Khan Aneal , Kulikowski Ewelina 
Published: June 2020

Abstract

Background and Aims
Fabry disease (FD) is a rare X-linked recessive genetic disorder caused by mutations in the α-galactosidase A gene. Absence or defects of this lysosomal enzyme lead to globotriaosylceramide (Gb3) accumulation. Gb3 disrupts basic cellular metabolic processes, inducing oxidative stress and promoting inflammation. Systemically, Gb3 accumulation leads to organ damage throughout the body with an increase in renal, cardiac, cerebrovascular and skin complications. Enzyme replacement therapy (ERT) is current standard of care. This therapy may reduce Gb3 deposits but the impact on cardiac and kidney function is unclear based on the limited studies. Further, ERT is less effective in the late phases of FD, partially due to the development of uncontrolled inflammation and fibrosis. Apabetalone is a clinical stage orally administered bromo and extra terminal domain inhibitor (BETi) that has beneficial effects on vascular inflammation and vascular calcification through an epigenetic pathway. Based on its mechanism of action and impact on multiple disease drivers in both preclinical and clinical studies, apabetalone has therapeutic potential to modulate inflammation in FD patients on ERT therapy.

Method
PBMCs and neutrophils were isolated from fresh blood of FD patients ± ERT therapy using density gradient centrifugation. The baseline immune status of PBMCs was compared in naïve FD patients (without ERT, n=3) and ERT treated patients (n=8) via flow cytometry. PBMCs or neutrophils from ERT patients were treated ex vivo with 5µM or 20µM apabetalone ± LPS stimulation. Expression of key pro-inflammatory mediators was analyzed with real time quantitative PCR. The production of reactive oxygen species (ROS) in neutrophils was assessed by flow cytometry.

Results
The PBMC inflammatory profile in baseline showed monocytes from ERT patients produced lower amounts of pro-inflammatory mediators (TNFα and IL6) than naïve patients (∼60%, trending p≤0.06 and p≤0.08 respectively). However, surface abundance of CCR2, a chemokine receptor for the MCP1 chemokine that promotes monocyte recruitment to local inflamed tissue during inflammatory process, was ∼2-fold greater on monocytes from ERT subjects than the naïve controls (trending p≤0.06). Gene expression of MCP1 was approximately 5-fold higher in PBMC from ERT patients versus naïve controls (p=0.01). In response to ex vivo LPS stimulation, PBMCs from FD patients on ERT showed a robust induction of pro-inflammatory responses with increases in gene expression of MCP1, IL12B, TNFA and IL6. Ex vivo treatment with apabetalone (5µM) blocked the LPS-induction of MCP1 gene expression (∼90%, p&lt;0.0001), and suppressed the upregulation of IL12B, TNFA and IL6 by 85%, 27% and 17%, respectively (p&lt;0.0001,p=0.04,p=0.004). In response to LPS stimulation, neutrophils induced reactive oxygen species (ROS), an indicator of oxidative damage caused by intracellular Gb3 deposit in FD patients, by ∼6 fold. Apabetalone treatment reduced this induction by 32% and 62% at 5µM and 20 µM, respectively (p=0.01, p=0.0007).

Conclusion
Monocytes from FD patients on ERT therapy display an enhanced expression of the CCR2-MCP-1 axis as compared to naïve controls, indicating the potential for immune cell tissue infiltration and local inflammation. Apabetalone counters this increase by preventing MCP1 gene transcription. Apabetalone also reduces PBMC mediated pro-inflammatory gene transcription (TNFA, IL12B, IL6) and neutrophil mediated ROS production in response to LPS stimulation. Therefore, apabetalone treatment may reduce pathological inflammation in FD patients and thus complement ERT to optimize patient outcomes, which will be tested further with warranted clinical studies.