Solution Oligonucleotide APIs: Regulatory Considerations

Manufacture of oligonucleotide active pharmaceutical ingredients (APIs) typically consists of solid-phase synthesis, deprotection and cleavage, purification and filtration, and isolation from aqueous solutions through lyophilization. In the first step of drug product manufacture, the API is dissolved in water again and excipients are added. While isolation of oligonucleotide APIs can be meaningful in many cases, there may be cases where keeping the API in solution provides benefit, and multiple technical aspects must be taken into account and balanced when determining the appropriate API form. A significant factor is whether an API in solution will contain additional components. While APIs in solution containing additional components (so-called formulated APIs) are well established for biological products, there are regulatory guidelines in place that represent hurdles for industry to using a formulated API approach for oligonucleotide drugs. The present communication outlines conditions where a formulated API approach can be chosen in compliance with existing guidelines. Relevant aspects pertaining to risk management, GMP standards, facility design, control strategies, and regulatory submission content are discussed. In addition, the authors propose that existing guidelines be modernized to enable the use of a formulated API approach for additional reasons than the ones described in the existing regulatory framework. The manuscript aims to promote a dialog with regulators in this field.