Disposables are increasingly being used in the manufacture of biopharmaceuticals. This article describes the design of a fully disposable process for the cGMP manufacture of clinical trial grade plasmid DNA. It addresses the rationale for implementing such a process with respect to the manufacture of patient-specific plasmid DNA vaccines for the treatment of leukemia. The process incorporates a number of disposable technologies, which are simple to use and thus reduce the need for investment in expensive equipment and cleaning validation.
The potential for treating a range of diseases by the delivery of DNA in vivo is being realized in the clinic in several different areas such as cancer, infectious diseases, and autoimmune diseases. The advantages of using naked pDNA over viral delivery routes include low immunogenicity (allowing a course of multiple treatments) and a simpler manufacturing system.1 The pDNA vector cassette is highly suitable for the rapid development of various vaccine targets, such as personalized vaccines. One limitation for pDNA vaccination is the relative efficiency of the targeting and delivery of pDNA, which is being currently addressed by improving delivery modes by either chemical or physical means (e.g., adjuvants, liposomes, gene gun, or electroporation).
The Clinical Biotechnology Centre (a part of the UK's National Blood Service) has manufactured a range of pDNA vaccines for academic collaborators, and those vaccines are currently undergoing Phase 1 and 2 trials. Since 2005, we have been involved in the manufacture of anti-idiotypic bespoke pDNA vaccines for patients suffering from multiple myeloma. This B-cell malignancy is characterized by the secretion of a serum immunoglobulin paraprotein, which can be identified molecularly and re-engineered into a single-chain Fv construct. The construct is cloned into the pDNA vector cassette containing an immunostimulatory tetanus toxoid fragment.2 Vaccination with the pDNA encoding the patient's paraprotein should induce the patient's immune system to mount anti-idiotypic responses against the tumor. The pDNA construct from one patient to the next may only differ by less than 2% of the backbone, making it suitable for designing a manufacturing platform. The vaccination regimen requires less than 50 mg of pDNA to be manufactured.
The promise of being able to deliver personally tailored vaccines for patients is a big challenge for the biopharmaceutical industry. Often, investments in such "orphan technologies" are not necessarily favored over more conventional generic approaches, where cGMP issues are less complex and the expected returns are greater. An ideal platform process would address the need to reduce manufacturing costs and allow rapid turnaround of batches of product.
Processing costs can be significantly reduced by eliminating the capital outlay in expensive, dedicated equipment (such as fermenters or chromatography systems) and opt for a process that is both disposable and simple to perform by an operator. A single-use process also eliminates the need for equipment decontamination procedures and cleaning validation studies, which are cumbersome and costly.
Some prerequisites are necessary to underpin the platform process to ensure compliance with current regulatory requirements. The appropriate sourcing of key materials is critical, such as the exclusion of animal-derived ingredients and the use of pharmaceutical-grade (USP, class VI) disposable plastics throughout. The prudent selection of the appropriate E. coli host cell and pDNA vector will also maximize plasmid quality and yields.3