Building an Immunotherapeutic
Creation of an autologous RNA-based immunotherapeutic begins by isolating precursors of a patient’s DCs and allowing them to mature in culture into functional antigen-presenting cells. These cells are then loaded with RNA collected and amplified from a patient’s tumor. The RNA can originate in cells sampled from the primary tumor site or distant metastatic sites, or present in the blood.
These RNA-loaded cells are the immunotherapeutic agent and can be administered to patients continuously over long periods of time. A single manufacturing run can produce enough autologous therapeutic to treat a patient for several years, eliminating costs associated with repeat production cycles and issues related to batch-to-batch variation.
Key challenges inherent in this type of autologous treatment approach based on the collection, manipulation, and delivery of live cells include the time line in which the cells must be collected, processed, and returned to the patient to ensure optimal viability and outcomes. Other considerations are the need to acquire and process patient samples from and distribute product to a large number of geographically diverse clinical sites and the need for adherence to stringent QA/QC measures throughout the manufacturing process.
Although each patient sample is processed individually, the goal is to follow standard operating procedures as identically as possible across samples. For autologous cell-based therapeutic approaches to be economically feasible, particularly within the current belt-tightening environment characteristic of managed health care and prevailing reimbursement philosophies, the manufacturing process must be optimized for cost efficiency.
It is unlikely that an autologous cell-based immunotherapeutic could be produced at commercial scale cost-effectively using manual methods. During product development, however, it may be too costly to implement automation. Ideally, as a company pursues product development and establishes proof of principle, it should begin, in parallel, to explore automated manufacturing techniques. Starting early to think about automation within the framework of process development will facilitate a more timely and seamless transition from manual to automated methods.
With all of these considerations in mind, Argos opted to establish a centralized manufacturing facility to develop and validate a manual production process capable of yielding sufficient product to meet the company’s needs through Phase II trials and to evolve toward a fully automated process to generate quantities required for pivotal trials and commercial-scale production. Underlying the concept of a centralized manufacturing strategy were three requirements: simplified process validation and quality control, minimal sample handling and manipulation at the clinical sites, and the flexibility to access patients and obtain samples at clinical sites distant from the central facility that might not be amenable to same-day collection and delivery of cells. Centralized production also offers the advantages of greater control over the process, enhanced traceability, and easier troubleshooting.
Ideally, to encourage participation, the clinical sites should have minimal responsibilities, limited to basic sample collection and preparation for transport. At the clincial site, prospective patients first undergo viral screening for at least HIV and hepatitis A, B, and C infection. The site then obtains a blood sample and prepares it for overnight shipping to the centralized processing facility. If the immunotherapeutic agent will target a cancer, the clinical site would also be responsible for providing a tumor sample or a blood sample, in the case of cancers of the hematopoietic system.
The day-old leukapheresis sample arrives at the manufacturing site, having been shipped at room temperature in the original cell-collection set. Due to the instability of plasma or leukapheresis samples, they must be processed within 96 hours of removal from the patient. A semi-automated procedure is used to isolate monocytes from the patient sample.
At this stage of the process, the enriched monocyte preparation can be frozen and stored until the RNA is prepared for loading into the DCs. To prepare the autologous kidney cancer immunotherapeutic that Argos is testing in ongoing clinical trials, RNA is extracted from a 400–500 mg surgical tumor sample and amplified.
The frozen monocytes are allowed to thaw and then remain in culture for six days, forming immature dendritic cells. On the sixth day, addition of a maturation formulation and continued overnight culture results in mature DCs that are harvested and co-electroporated with the amplified tumor RNA and CD40L RNA. The CD40L RNA is co-electroporated to improve dendritic cell potency by stimulating IL-12 production. Culturing of the RNA-loaded cells for four hours post-electroporation is followed by harvesting and formulation into the final product. This then undergoes QC testing, freezing, and cryogenic storage. The final formulation can then be shipped on demand to a clinical site for administration to the patient.
At present, this entire process—except for the semi-automated techniques employed for monocyte isolation—relies on manual methods. QC measures are in place to track and manage patient specimens (from the clinical site to the manufacturing site), raw materials, manufacturing components, and final immunotherapeutic product.