Presented by: René Thürmer, PhD, Deputy Head, BfArM (Federal Institute for Drugs and Medical Devices, Germany)
Dr. René Thürmer started his presentation taking a look at the peptide and oligonucleotide market. Currently, there are many peptide drugs on the market, including some generics. While the number of oligonucleotide drugs is growing, there are currently no generics for this class of drug. Both drug classes are synthesized using solid phase chemistry and purified using chromatographic techniques.
Although the limits defined in ICH Q3A/G do not apply to either class, the presence of impurities is a main cause of concern for regulatory agencies. For an Investigational New Drug (IND) application to be awarded it is important in Module 3 of the Common Technical Document (CTD) to have a detailed description of the manufacturing processes. This includes definitions of batches, scale and operating ranges, and reprocessing/repurification steps should be described and validated. The speaker noted that it is becoming more common for a second chromatographic step to be included in newer peptide drug applications.
Dr. René Thürmer at TIDES Europe 2021
Quality of starting materials is a very important consideration in the manufacture of a peptide or oligonucleotide drug. With use of complex starting materials comes the need to comply with ICHQ11 Q&A guidelines, it also requires a more detailed description than use of simpler protected amino acid derivatives or phosphoramidites. Because impurities in starting materials may be integrated into the final oligonucleotide product, assessment for presence of starting material impurities is critical. The section of the application “on control of critical steps and intermediates”
is also important. As part of the control strategy, definitions of routine and in-process control testing and alerts for rejection limits should be included, as well as description and validation of the analytical methods.
The presence of impurities is the main cause of concern for regulatory agencies.
Dr. Thürmer explained that process validation is the same for peptides and oligonucleotides. He emphasized the importance of this section, and shared that recent submissions to his agency had been of a high standard. He also shared that a few applications had encompassed design space, and in those, the concept was limited to certain manufacturing steps.
He discussed the standard characterization methods that are expected for validation of peptides (MS/MS, peptide mapping, 2D NMR, disulfide bonding) and oligonucleotides (spectroscopy, differential scanning calorimetry, melting temperatures, etc.). For conjugated oligomers and aptamers additional characterization requirements are expected, such as bioassays confirming binding function. Consistency in the manufacturing processes must be demonstrated regarding issues in stereochemistry. For racemization studies in peptides, for example, chiral GC analysis is expected. Whereas for oligonucleotides, justification and explanation of the presence mixtures of diastereomers should be included.
Regarding the sources, analysis, and control of impurities the key factors are safety and manufacturing consistency, said Thurmer. Oligonucleotides have complex impurity profiles and it is common to group the impurities in the documentation. If this method is employed the times and types of groups need to be specified. Impurity threshold limits for peptides and are defined in the European Pharmacopoeia Monograph “Substances for Pharmaceutical Use.” Because there are no defined limits for oligonucleotides, they are considered on a case-to-case basis. Thresholds suggested by Capaldi et al. in “Impurities in Oligonucleotide Drug Substances and Drug Products" - Nucleic Acid Therapeutics, 27(6), Dec. 2017, are often followed for oligonucleotides. He noted that some recent submissions have reported lowered threshold values. In setting purity specifications for manufacturing process validation, manufacturing capabilities and clinical and toxicological qualified limits are considered. If there are insufficient batch samples to set routine manufacturing specifications, post-approval assessment may be an option. Process related impurities have to be discussed and their impact on safety addressed, with the final the approach justified by the applicant.
Dr. Thürmer clarified that although peptides and oligonucleotides are excluded from ICHM7(Rl) guidelines, compliance is still expected by the agencies. Applicants must also address nitrosamine impurities in the product; risk evaluation should be included in Module 1 and perhaps referenced to in module 3, 3.2.P.5.6 (Justification of Specification). Orthogonal purification methods are recommended for both peptides and oligonucleotides. Ultra-performance liquid chromatography (UPLC) is common for peptide analysis, but additional methods are required for dimers, multimers and aggregates.
Combination of RP-HPLC and ion-exchange chromatography or LC-MS may be employed for antisense oligonucleotides or to control single-strand intermediates for double-stranded oligonucleotides. He noted that duplex applicants will need a combination of non-denaturing and denaturing methods or two orthogonal denaturing methods.
Because stability issues are more common in peptides, testing should be carried out early in development (Phase I), data from early batches aid in shelf-life determination and detection of alterations in analytical methods. Thurmer said that stress testing should be used to identify stability issues.
Because stability issues are more common in peptides, testing should be carried out early in development.
Lastly, for assurance of sterility, terminal sterility in the final container must be attempted. There are guidelines and decision trees for the selection of sterilization method, and efforts to develop a formulation and container capable of terminal sterilization should be presented. If the degradation products a can be identified as previously qualified impurities or metabolites, terminal sterilization is considered feasible and is the method of choice, otherwise sterile filtration and aseptic processing may be selected.
The audience Q&A covered use of reference data for consistency of starting materials in oligonucleotide synthesis, the eradication of lyophilization and the possibility of liquid products. Lastly it was clarified that nitrosamine assessment was not required during Phase 1/2.
About the Speaker Dr. René Thürmer received his diploma in chemistry and his PhD in biochemistry from the University of Tübingen. He joined the BfArM (Federal Institute for Drugs and Medical Devices, Bonn, Germany) in 2000. He currently serves as a CMC reviewer and is Deputy Head of the Unit Pharmaceutical Biotechnology.
