The history of the established cell line has to be traceable: the host cell line, the laboratory where the host cell line was once isolated, or the culture collection where it was originated. Full documentation of passages, media, and media components, preferably with material certificates, is necessary. The sources of recombinant genes, expression systems, and cloning are well documented. Recombinant cell clones generated in the laboratory are screened for suitability (expression level, expression stability, and required posttranslational modifications).
Master cell bank
A master cell bank (MCB) consisting of 200-300 vials is manufactured from a suitable cell clone and is tested for purity, identity, amount of viable cells, and suitability. GMP-compliant storage of the MCB is performed at low temperatures, that is, in the gas phase of liquid nitrogen or in an ultra-deep freezer at < -150 °C.
A scalable laboratory cultivation process is subsequently developed. Set points, proven acceptable ranges, and edges of failure of individual process parameters have to be established. The composition of the growth medium is optimized with respect to cell and process requirements.
Working cell bank
One vial of the MCB is expanded in growth medium and aliquoted as working cell bank (WCB) into > 300 vials, which are then cryoconserved in a GMP process comparable to that of the MCB. Like the MCB, the WCB is tested and characterized with regard to purity, identity, content, and viability. For animal cells, special emphasis is placed on virus safety testing.
The cultivation regime is scaled up to technical (i.e. manufacturing) scale. Process parameters and target substance quality are monitored and controlled.
Based on the two intermediates, a) cell mass or b) cell-free supernatant (depending on where the cell deposits the target substance), a purification scheme consisting of a sequence of chromatography and filtration units is established. Set points, proven acceptable ranges, and edges of failure for the parameters of each unit operation are established with respect to target substance integrity, step yield, and purity. In the purification sequence for target substances generated from animal cell cultures, steps for virus removal (inactivation, nanofiltration) are implemented. The purification sequence is scaled up to technical and manufacturing scale.
Analytical procedures and in-process controls
For all stages of process development, analytical procedures suitable for characterizing the product with regard to identity, activity, content, and impurities are established. Analytical procedures used for the testing of incoming starting materials, release of target substance, and critical steps within the manufacturing sequence have to be validated for their purpose and in compliance with the requirements of the ICH Q2 guideline.
Verification of cleaning procedures
Cleaning procedures for all multi-use equipment components that are in direct contact with the target substance are verified for cleaning success on the basis of visual inspections, target substance carryover, and total organic carbon. Acceptance criteria for equipment cleaning procedures are established with risk-based approaches.
Stability data for almost all unit operations in the purification sequence are recorded. Potential holding points for intermediates in the process sequence and storage conditions for intermediates are identified. Stability data for the purified bulk drug substance are generated in compliance with the requirements of the ICH Q5C/Q1A guidelines for standard and challenged storage conditions. Expiry and retesting dates are derived.
The results of cell line development, process development, analytical development, and stability data are documented and condensed in development reports. Critical parameters for process and equipment are addressed in a preliminary risk-based validation master plan. A master batch production record and a master batch analysis record addressing all aspects of process and target substance quality (identity, purity, activity, and content) are prepared.
Manageability of the master batch production record and the batch analysis record is verified by execution of a minimum of one technical batch in the GMP facility. Target substance material (purified bulk) from the technical batch may be used in preclinical research and serve as reference standard.
An application for a manufacturing license according to §13 of the German Drug Act is filed with the local drug authorities. In direct consultation with the German Federal Institute for Drugs and Medical Devices (BfArM) or the Paul Ehrlich Institute (PEI), the local drug authorities will decide about the manufacturing license within 100 days. The decision about the manufacturing license is based on process documentation quality, inspection of the manufacturing facility, qualification of the operating personnel, and the quality assurance system in place to guarantee compliance with local applicable GMP regulations.
GMP manufacture of clinical-grade target substance
Once the manufacturing license has been issued, one or several GMP batches of the target substance are manufactured, analytically tested, and released.