Adding a Second API Source: What Your QA Department Will Ask

A second source is not a second purchase order. Adding an API supplier to an approved dossier is a change to a marketing authorisation, and it generates a document set before a kilogram can legitimately be used. For an animal-derived substance such as a bile acid it generates a document set with one extra step that has no equivalent for a synthetic small molecule.

I would put it this way to anyone weighing a second source on price alone: the material may be cheaper, and the project has a cost. Understanding the size of that cost is what this page is for.

It lands in the variation framework

In the European system, changes to the substances in a marketing authorisation are classified in a published guideline, and the class determines how much assessment is involved and whether the change can be implemented before approval. The sub-case matters more than the headline, because the same nominal change can be a routine notification or a heavily assessed variation depending on circumstances.

One practical warning about the framework itself. The classification guideline was revised in 2025 and the quality sections were renumbered, so a reference to a clause number lifted from a 2019 training slide may point at the wrong place in the current text. Cite the current version, and check the numbering rather than assuming it.

Two paths, and a CEP changes everything

Whether a Certificate of Suitability is involved decides which authority you are dealing with and how long the exercise takes.

Where the substance is covered by a CEP, the substance and its process have already been assessed by EDQM, and changes to the manufacturing site and process are handled through EDQM's own change procedures rather than through a fresh submission to a medicines agency. EDQM revises its guidance on CEP changes periodically, and the current version adds further situations that call for a new certificate application rather than a variation to an existing one. That distinction is worth checking early, because it changes the timeline by months rather than weeks.

Where the substance is described in the dossier or in an Active Substance Master File, the change goes through the medicines agency and the full machinery applies: a comparative assessment, updated dossier sections, and declarations from the qualified persons involved.

The bearing on bile acids is direct. A pharmacopoeial substance with a monograph can hold a CEP; a substance with no monograph cannot, which is the structural reason covered in our note on which regulatory document your market needs. If you are sourcing a molecule that falls outside the pharmacopoeias, the CEP route is not available to you at all and the second source automatically means the heavier path.

The document set a second source generates

Sub-case aside, the same core items appear, and they are the ones to ask for early rather than at the end.

• Comparative batch analysis data for at least two batches, at minimum pilot scale, from the current and the proposed source, presented in a comparative tabular format
• A declaration from the dossier holder that the synthetic route, quality control procedures and specifications are unchanged, where that is the claim being made
• TSE documentation for any new animal-derived source, which for this family is not optional
• Qualified person declarations covering GMP compliance of the sources involved
• Amendments to the relevant dossier sections, in the applicable CTD format
• A change-notification commitment from the substance producer, covering future changes to process, specification and test methods

The comparative batch table is where most of the value sits, and it is worth reading properly rather than checking that it exists. Two batches of a bile acid from two routes can meet the same pharmacopoeial specification and still differ in the unspecified impurity profile, in the residual solvent set, and in physical properties such as particle size distribution. Our piece on the two synthesis routes sets out where those differences come from. A comparative table that shows only the pass or fail outcome for each parameter has not shown you anything.

The extra step for an animal-derived substance

This is the part that makes a bile acid second source different from a typical small-molecule one, and it is the part most often underestimated.

Where material of animal origin enters the process, the change package has to address the TSE risk. In practice that means either a TSE Certificate of Suitability for the new source, or documentary evidence that the specific source has previously been assessed by a competent authority as compliant with the relevant guidance on minimising the risk of transmitting animal spongiform encephalopathy agents. The information required is specific rather than general: the name of the producer, the species and tissues the material derives from, the country of origin of the source animals, its use, and where it was previously accepted. For a centralised procedure, this feeds an updated TSE table in the dossier.

Two consequences follow. First, a generic statement that a material is TSE-free is not a document; the classification framework asks for traceable specifics about species, tissue and country. Second, a second source that switches species of origin is a heavier exercise than one that does not, because the underlying risk assessment changes rather than merely being re-papered.

I would go further and say this is the point at which the paperwork stops feeling like paperwork. Everything else in this article is administrative. Species and country of origin are statements about where the material physically came from, and they have to be true.

What the buyer should do in parallel

The dossier work is the dossier holder's job, and the buyer's own work runs alongside it. Three things are worth doing from the start rather than after the variation is filed.

1. Get the impurity profile comparison, not the specification comparison. Ask for the chromatograms or the peak tables, and compare the unspecified region between the two sources.
2. Run the second source through your own related-substances method before committing to it in a filing, so that a method transfer problem surfaces while it is still cheap to change your mind.
3. Check the physical form, not just the chemistry. Particle size distribution and crystallinity affect how the material behaves in your process, and a change of source is a common cause of a sudden change in compressibility on the line.

The case for a second source is usually made on supply risk, and the argument is sound. The market for this molecule is concentrated enough that a single-source position is a genuine exposure, as set out in our note on concentration risk. What I would push back on is the assumption that a second source is free once the material is qualified. It is not, and the invoice arrives in regulatory and analytical hours rather than in currency.

Frequently asked questions

Does adding a second API source require a regulatory submission?

Yes. In the European framework it is a change to the marketing authorisation, classified in the variation guideline. The sub-case decides whether it is a notification or a variation requiring assessment.

Does a CEP make a second source easier?

It changes the route. Where a CEP covers the substance, changes to the site and process are handled through EDQM's certificate change procedures. Where there is no CEP, the change goes through the medicines agency with a comparative assessment.

What batch data is needed for a second source?

Comparative batch analysis data for at least two batches, at minimum pilot scale, from the current and proposed source, presented in a comparative tabular format.

Is a TSE statement enough for an animal-derived API?

Not usually. The framework asks for a TSE Certificate of Suitability for the new source, or documented evidence of prior assessment, including the producer, the species and tissues, the country of origin of the source animals and the previous acceptance.

Is the material interchangeable if it meets the same specification?

Not necessarily. Two sources can meet the same pharmacopoeial specification with different unspecified impurity profiles, residual solvent sets and physical properties. Compare the profiles rather than the pass or fail outcomes.

Can a second source be used before the variation is approved?

That depends on the category. Some changes can be implemented and notified within defined timeframes; others require approval beforehand. The category has to be established before any material is used, not after.

The question to ask before the second source is agreed

Ask what changes in the comparative batch table. If the answer is that both sources pass every specification line, the analysis has not been done yet. The differences worth knowing about live in the columns that pass.

The primary references behind this piece are the European Commission guideline on the categories of variations, EDQM's Certificates of Suitability pages and the EMA material on TSE risk assessment. The classification guideline was revised in 2025; check the current numbering rather than quoting an older reference.

What we ship against is on the ursodeoxycholic acid page, and the document package for a specific market and quantity can be raised through a quotation request.

This article describes regulatory change categories and documentation for quality, regulatory and procurement professionals. It states no therapeutic use, dose or indication for any substance, and no order quantity or lead time. Variation categories and their numbering change; confirm against the current published guideline before acting.