The API Contract Manufacturing Process, Step by Step

Once you've decided you need a contract manufacturing partner rather than a development (CDMO) relationship, the next question is usually: what actually happens after you sign? Here is the general process, stage by stage.

If you have decided you need a contract manufacturing partner rather than a development (CDMO) relationship, here is what actually happens after you sign — the general process, stage by stage.

Step 1: Specification and documentation review

You provide your existing manufacturing specification, analytical test methods and any relevant regulatory documentation (prior CoAs, stability data if available). The manufacturer reviews this for feasibility against their own equipment, capacity and regulatory scope before quoting — this step exists to catch mismatches early, not to rubber-stamp the request.

Step 2: Technical feasibility and costing

The manufacturer assesses whether the specification can be run as-is on their equipment, what raw materials and intermediates are required, and where in their production schedule the work fits. This is where MOQ, batch size and lead time get confirmed — ask for these numbers explicitly rather than assuming a standard figure, since they vary by compound and manufacturer.

Step 3: Technology transfer (tech transfer)

This is the most document-heavy stage: your process documentation, analytical methods and specifications are formally transferred to the manufacturing site’s quality and production teams. A well-run tech transfer includes a gap analysis — comparing your original process parameters against what is achievable on the receiving site’s actual equipment — rather than assuming a one-to-one copy is possible without adjustment.

Step 4: Trial or engineering batch

Before committing to commercial-scale production, most contract manufacturing engagements run a trial (engineering) batch — often at a smaller or intermediate scale — to confirm the transferred process performs as expected on the new equipment. This batch is analyzed against your original specification, and any deviations are investigated and resolved before scaling further.

Step 5: Validation (where required)

Depending on your regulatory requirements and destination market, one or more validation batches may be needed to formally demonstrate the process is reproducible at commercial scale, in line with your quality system and any relevant CDSCO or export-market expectations. This stage is typically driven by your own regulatory strategy — confirm with the manufacturer how they support it.

Step 6: Commercial batch production and release

Once validation (where applicable) is complete, commercial batches proceed against agreed production schedules. Each batch should ship with a Certificate of Analysis specific to that batch — not a generic specification sheet. See our guidance on what to confirm about CoA practice before you are at this stage.

Step 7: Ongoing supply and quality agreement management

A contract manufacturing relationship does not end at the first commercial batch — ongoing supply typically runs under a formal quality agreement covering change control (any proposed modification to the agreed process requires your sign-off), deviation handling and re-order lead times. Confirm how change control is managed before you commit long-term.

What to confirm before you start

• MOQ and batch size range for your specific compound
• Realistic timeline from spec handover to first commercial batch
• Whether a trial / engineering batch is included or billed separately
• CoA issuance practice per batch
• Change control process for the life of the agreement

Frequently asked questions

How long does the full process typically take, from signing to first commercial shipment? This depends heavily on compound complexity, whether a trial batch reveals any issues, and your validation requirements — ask for a realistic project timeline specific to your compound rather than a generic industry average.

What’s the difference between this process and a CDMO engagement? Contract manufacturing assumes your specification is already validated and ready to transfer; a CDMO engagement starts earlier, with process development itself. See CDMO vs. CMO: what’s the real difference if you are not yet sure which you need.

Who owns the manufacturing IP in a contract manufacturing arrangement? This is defined by your contract terms, not assumed by default — confirm IP ownership and confidentiality terms explicitly before sharing your specification.