When selecting a fill-finish CDMO, many sponsors review capabilities, capacity, and quality history. While these factors are important, they do not provide a complete picture of a CDMO’s quality and performance.
Comparing fill-finish CDMOs can also be difficult when each presents its capabilities differently. To make a true apples-to-apples comparison, sponsors should ask for the same set of data-driven answers from every partner under consideration.
Below we list several key questions to ask when evaluating a fill-finish CDMO.
Filling Technology
Question to ask:
- Please describe your filling line. Do you fill in isolators?
- Not all aseptic processing environments provide the same level of sterility assurance. Understanding whether a fill-finish CDMO operates with isolators or Restricted Access Barrier Systems (RABS), and how operator interventions are controlled, can significantly impact contamination risk, batch quality, and consistency.
- The CDMO should clearly explain the barrier technology used and how it minimizes operator interaction. The equipment that controls the environment around the sterile core where aseptic filling occurs has a significant impact on sterility assurance.
- Isolator-based filling offers a high level of sterility assurance by physically separating operators from the aseptic processing environment and using a validated decontamination cycle prior to filling. Isolators are preferred by both FDA and EU regulators. RABS are also used in sterile manufacturing but provide a lower level of sterility assurance due to greater reliance on operator interaction and cleaning.
What to look for:
- Isolator-based sterile core
- Fully automated filling systems that minimize operator intervention and improve consistency and repeatability
- Segregated capping station for vials to reduce the risk of particulate contamination in final filled containers
Quality Metrics
Questions to ask:
- What has been your batch success rate over the last 24 months?
- What is your deviation rate per batch (critical, major, minor) over the last 24 months?
- Every fill-finish CDMO tracks these quality performance metrics, and a high-quality CDMO should be willing to share them transparently.
What to look for:
- High batch success rates
- Low and well-characterized deviation rates
Yield & Efficiency
Questions to ask:
- What is your batch yield rate over the last 24 months?
- How do you perform weight checks?
- What is your average visual inspection reject rate over the last 24 months?
- For high-value or orphan drug products, small losses can have a significant impact on clinical supply and manufacturing costs. The sterile fill-finish process has several loss points, and CDMOs that focus on small-batch filling should actively work to minimize them.
What to look for:
- Low line losses (hold-up volume, priming losses)
- Non-destructive weight checks
- Low visual inspection reject rates
- Non-destructive container closure integrity testing (CCIT) when performed onsite
Every Milliliter Matters
For high-value drug products, even small amounts of product loss can have a significant impact. Learn where product is commonly lost during fill-finish, and the strategies that can help maximize yield.
Timelines & Reliability
Questions to ask:
- What is your target release timeframe for drug product batches?
- What percent of batches were released on time in the last 24 months?
- Have you ever impacted a clinical trial or packaging event?
- Timelines should be both defined and reliable. A strong fill-finish CDMO demonstrates consistent performance and, if delays occur, works to prevent or minimize the impact on downstream activities.
What to look for:
- Realistic release timelines (including dependencies such as external testing)
- High on-time batch release rates
- Minimal to no history of impacting clinical or commercial milestones
Contamination Control
Questions to ask:
- Have you had any contamination issues or sterility failures in drug product batches?
- What is your media fill success rate?
- Contamination control is non-negotiable in sterile manufacturing. A single sterility failure can result in batch loss, regulatory action, and, most importantly, patient risk. Sponsors should understand both a fill-finish CDMO’s contamination control strategy and its demonstrated performance.
What to look for:
- Zero product sterility failures
- 100% media fill success rate
- A clearly defined contamination control strategy aligned with current regulatory expectations
Regulatory Compliance
Question to ask:
- What regulations does your quality system support (e.g., US, EU, other)?
- Global programs require alignment across regulatory bodies. Sponsors should understand whether a fill-finish CDMO’s quality systems and manufacturing practices support the regulatory requirements of their intended markets. EU GMP Annex 1 sets rigorous expectations for sterile manufacturing and contamination control, making Annex 1 compliance an important benchmark even for programs not currently intended for EU markets.
What to look for:
- US FDA requirements
- EU GMP Annex 1 expectations
- Other global agencies (e.g., PMDA, Health Canada)
Why This Matters
It’s difficult to evaluate fill-finish CDMOs based on capabilities, capacity, and quality history alone. Evaluating across these dimensions, the differences in risk, yield, and reliability become clear. We hope these questions help inform your search for a fill-finish CDMO that best fits your product, program, and long-term manufacturing needs.
Explore Argonaut’s Current Capacity
Argonaut has vial filling capacity available in 2026, with syringe and cartridge capacity available in 2027. Explore our fill-finish capabilities, take a virtual facility tour, and connect with our team to discuss your program.
