Impact of Excipients on Stability of Polymer Microparticles for Autoimmune Therapy.

Emily A Gosselin,Sheneil K Black,Christopher M Jewell,Maeesha Noshin

doi:10.3389/fbioe.2020.609577

Abstract

Therapies for autoimmune diseases such as multiple sclerosis and diabetes are not curative and cause significant challenges for patients. These include frequent, continued treatments required throughout the lifetime of the patient, as well as increased vulnerability to infection due to the non-specific action of therapies. Biomaterials have enabled progress in antigen-specific immunotherapies as carriers and delivery vehicles for immunomodulatory cargo. However, most of this work is in the preclinical stage, where small dosing requirements allow for on-demand preparation of immunotherapies. For clinical translation of these potential immunotherapies, manufacturing, preservation, storage, and stability are critical parameters that require greater attention. Here, we tested the stabilizing effects of excipients on the lyophilization of polymeric microparticles (MPs) designed for autoimmune therapy; these MPs are loaded with peptide self-antigen and a small molecule immunomodulator. We synthesized and lyophilized particles with three clinically relevant excipients: mannitol, trehalose, and sucrose. The biophysical properties of the formulations were assessed as a function of excipient formulation and stage of addition, then formulations were evaluated in primary immune cell culture. From a manufacturing perspective, excipients improved caking of lyophilized product, enabled more complete resuspension, increased product recovery, and led to smaller changes in MP size and size distribution over time. Cocultures of antigen-presenting cells and self-reactive T cells revealed that MPs lyophilized with excipients maintained tolerance-inducing function, even after significant storage times without refrigeration. These data demonstrate that excipients can be selected to drive favorable manufacturing properties without impacting the immunologic properties of the tolerogenic MPs.

Highlights

Polymeric particles and scaffolds have been widely researched as carriers for biologics and small molecules to improve delivery of cargo to cell and tissue targets (Nair and Laurencin, 2007; Ulery et al, 2011; Danhier et al, 2012; Fenton et al, 2018)
We show that low concentrations of Enc and externally incorporated (Ext) excipients enhance the stability of MPs after 5 months in storage at room temperature
Three excipients were selected based on previous research on protein stabilization in PLGA particles— mannitol, sucrose, and trehalose

Summary

Introduction

Polymeric particles and scaffolds have been widely researched as carriers for biologics and small molecules to improve delivery of cargo to cell and tissue targets (Nair and Laurencin, 2007; Ulery et al, 2011; Danhier et al, 2012; Fenton et al, 2018). One important emerging area applies these carriers to immunotherapies by delivering peptides recognized by the immune system (antigens) and immune cues to modulate immune response (Andorko et al, 2015; Northrup et al, 2016; Tostanoski et al, 2016b; Bookstaver et al, 2018; Ben-Akiva et al, 2019). Using a simple, scalable degradable polymer [poly(lactideco-glycolide), PLGA], we developed microparticle (MP) depots that promote regulatory immune function and reverse disease in preclinical models of MS. These depots recondition the local environment of lymph nodes—tissues that coordinate immune function—by co-delivering myelin self-peptide (MOG) and an immunomodulatory cue, rapamycin (Rapa). This shifts the response to myelin away from inflammation and toward tolerance in a selective fashion (Tostanoski et al, 2016a)

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