Pilot-scale production of expansile nanoparticles: Practical methods for clinical scale-up

Our plain-English summary of Pilot-scale production of expansile nanoparticles: Practical methods for clinical scale-up, by A.H. Colby, R. Liu, R.P. Doyle, et al (Journal of Controlled Release, 2021).

The study

• Authors: A.H. Colby, R. Liu, R.P. Doyle, A. Merting, H. Zhang, N. Savage, N.Q. Chu, B.A. Hollister, W. McCulloch, J.E. Burdette, C.J. Pearce, K. Liu, N.H. Oberlies, Y.L. Colson, M.W. Grinstaff
• Journal: Journal of Controlled Release
• Published: 2021;337:144-154
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

One of the foremost challenges in translating nanoparticle technologies to the clinic is the requirement to produce materials on a large-scale. Scaling nanoparticle production methods is often non-trivial, and the success of these endeavors is frequently governed by whether or not an intermediate level of production, i.e., "pilot-scale" production, can be achieved. Pilot-scale production at the one-liter scale serves as a proof-of-concept that large-scale production will be possible. Here, we describe the pilot-scale production of the expansile nanoparticle (eNP) technology including verification of activity and efficacy following scaleup. We describe the challenges of sonication-based emulsification procedures and how these were overcome by use of a Microfluidizer technology. We also describe the problem-solving process that led to pre-polymerization of the nanoparticle polymer-a fundamental change from the lab-scale and previously published methods. Furthermore, we demonstrate good control over particle diameter, polydispersity and drug loading and the ability to sterilize the particles via filtration using this method. To facilitate long-term storage of these larger quantities of particles, we investigated six lyoprotectants and determined that sucrose is the most compatible with the current system. Lastly, we demonstrate that these changes to the manufacturing method do not adversely affect the swelling functionality of the particles, their highly specific localization to tumors, their non-toxicity in vivo or their efficacy in treating established intraperitoneal mesothelioma xenografts.

Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.

In plain English

This laboratory study described scaling up manufacture of paclitaxel-loaded expansile nanoparticles (PTX-eNPs). These tiny particles swell in mildly acidic conditions and were developed to treat peritoneal tumors. The article does not concern asbestos exposure. The authors made the starting chemical at a 1 kg scale. They changed the method by forming the polymer before emulsification and passing the probe-sonicated emulsion through a high-pressure Microfluidizer device. A one-liter batch had a mean particle diameter of 40 nm, a polydispersity of 0.1 and paclitaxel loading of 93%. The particles could be sterilized by filtration. After freeze-drying with 5% sucrose, diameter was not significantly different after 1 or 3 months' storage. The new particles swelled in acidic laboratory buffer, and in mice they gathered in tumors. Healthy mice (3 per group) showed no adverse clinical observations. In mice with intraperitoneal mesothelioma tumors (8 per group), median survival was 39 days with saline and 55 days with a Taxol-like formulation. More than 60% of mice in both nanoparticle groups survived to day 90. The authors concluded that pilot-scale production kept particle properties and in vivo safety and efficacy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory manufacturing scale-up study with mouse experiments (toxicity, tumor localization and survival)
• Who was studied: Mice. Six- to eight-week-old female athymic nude (NU/J) mice were given intraperitoneal MSTO-211H-luc mesothelioma tumor cells, with 8 per group in the survival study. Eight-week-old female C57BL/6 healthy mice were used for toxicity testing, 3 per group.
• Exposure: No asbestos exposure was studied. The treatments compared were pilot-scale PTX-eNPs, historical PTX-eNPs, paclitaxel in Cremophor EL/ethanol (Taxol mimic) and saline. Each was given intraperitoneally in four weekly doses, with paclitaxel at 10 mg/kg per week.
• Main results:
  • The eNP monomer was synthesized at a 1 kg scale with yields of 98% for the first step, 85% for the second step and 83% overall.
  • In the new pilot-scale method, the pre-formed eNP polymer and paclitaxel were first emulsified by probe sonication. The emulsion was then processed on the LV1 Microfluidizer.
  • The one-liter pilot-scale batch had a mean diameter of 40 nm, a PDI of 0.1 and paclitaxel loading of 93%.
  • Filtration through a 0.22 um filter did not significantly change particle diameter, PDI or paclitaxel loading.
  • Of six lyoprotectants screened, 5% sucrose was selected. Freeze-dried particle diameter was not significantly different after 1 or 3 months of storage under either storage condition.
  • In laboratory buffers, pilot-scale particles at pH 7.4 did not change in diameter. Particles exposed to pH 5 swelled 2- to 10-fold.
  • In mice bearing established intraperitoneal tumors, rhodamine-labeled PTX-eNPs accumulated in tumors throughout the peritoneum.
  • In healthy mice given PTX-eNPs or saline, there were no adverse clinical observations and body weights did not differ significantly. Albumin and ALT differed statistically between groups, which the authors described as not clinically relevant.
  • In mice with established intraperitoneal mesothelioma, median survival was 39 days with saline and 55 days with the Taxol mimic.
  • Both the historical and the pilot-scale PTX-eNP groups significantly improved survival compared with these controls, with more than 60% of both groups surviving to the study end at 90 days. Survival did not differ significantly between the two PTX-eNP formulations.
• The authors' conclusion: The authors concluded that the new Microfluidizer-based process achieved pilot-scale production while keeping the target particle diameter and PDI, swelling function, and in vivo safety and efficacy.
• Limitations the authors state:
  • Further scale-up to multi-liter, continuous-flow production was beyond the scope of the study.
  • The long-term storage stability studies were still ongoing.
  • The process still uses hazardous materials such as halogenated solvents, which the authors intend to try to remove.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma.

Related studies

• Radiolabeled Biodistribution of Expansile Nanoparticles: Intraperitoneal Administration Results in Tumor Specific Accumulation — A.H. Colby, J. Kirsch, et al. (2023)
• Nanoparticle drug-delivery systems for peritoneal cancers: a case study of the design, characterization and development of the expansile nanoparticle — A.H. Colby, N.H. Oberlies, et al. (2017)
• Paclitaxel-loaded expansile nanoparticles enhance chemotherapeutic drug delivery in mesothelioma 3-dimensional multicellular spheroids — H. Lei, S.C. Hofferberth, et al. (2015)
• Paclitaxel-loaded expansile nanoparticles in a multimodal treatment model of malignant mesothelioma — M.D. Schulz, K.A. Zubris, et al. (2011)
• Nanoparticle tumor localization, disruption of autophagosomal trafficking, and prolonged drug delivery improve survival in peritoneal mesothelioma — R. Liu, A.H. Colby, et al. (2016)
• Two-Step Delivery: Exploiting the Partition Coefficient Concept to Increase Intratumoral Paclitaxel Concentrations In vivo Using Responsive Nanoparticles — A.H. Colby, R. Liu, et al. (2016)

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