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What belongs in CTD 3.2.S.1 drug substance general information?
Describe the substance’s verified names, molecular or biological identity and relevant general properties. Keep material forms and measurement conditions explicit, and use the same identity throughout the dossier. Section S.1 states what the material is; the characterization section explains the evidence establishing that identity.
Before you begin
M4Q(R1) drug-substance identity; chemical and biotech branches differ. FDA v4 places these narrative subjects under 3.2.S.1.
What you will prepare: A consistent identity section linked to supporting characterization and formulation decisions.
Nomenclature: make aliases resolve to one substance
Collect the controlled substance record, naming decisions, supplier identifiers and the names used in studies. Present the applicable nonproprietary, chemical, compendial and development names with their roles; include a registry identifier only when verified for the actual substance. A proposed name should remain visibly proposed. Keep salts, solvates and active moieties distinct.
Build an editorial alias table: name, type, record establishing it, and where it appears elsewhere. Check the cover information, S.2 process, S.4 specification and study batch records against it. If two codes might refer to different forms, ask the chemistry owner to resolve identity rather than replacing one globally.
Structure: show what material the dossier describes
For a chemical substance, prepare the structural formula with the relevant stereochemistry, molecular formula and relative molecular mass from an approved identity record. Review whether the stated mass refers to the free form or the submitted salt/solvate. For biotech material, use the applicable sequence representation, modifications and mass description; a single small-molecule drawing is not an adequate replacement.
S.1 states identity. S.3.1 explains how the evidence establishes it. Link the two, and make uncertainty visible. An unassigned modification or unresolved stereochemical question should not disappear into a polished figure caption.
General properties: connect observations to their conditions
Select physicochemical and other properties relevant to the substance; include biological activity for biotech material as appropriate. Record units and measurement conditions beside values when their meaning depends on pH, temperature, medium or method. Obtain the records from characterization, preformulation and analytical teams rather than copying a supplier brochure.
Fictional exercise: a solubility value measured for a free base is pasted into a salt dossier. Resolve the material identity and conditions first; then replace or qualify the entry and review P.2's formulation rationale. The output should help the reader understand formulation-relevant attributes without presenting an observation as a universal constant. Unknown conditions require a source query, not an invented footnote.
Use an identity reconciliation sheet
A useful S.1 working sheet tracks each representation of the substance and the record that establishes it. This is an editorial control, not an agency form.
| Representation | Check against | Mismatch to resolve |
|---|---|---|
| Name or development code | Controlled identity record and study material records | One code used for different salts or manufacturing materials |
| Formula or sequence | Approved structural description | Missing counterion, modification or stereochemical qualification |
| Molecular mass | Stated material and calculation basis | Free-form mass paired with a salt formula |
| General property | Method, material, units and conditions | Solubility reported without the medium or pH that defines it |
Read each property as a conditional statement: “For this material, measured under these conditions, this result was obtained.” That exercise exposes values copied from brochures or neighboring products whose conditions are unknown.
Fictional review: an assay calculation uses the active moiety, while S.1 gives the salt identity. Both may be appropriate in their own contexts. Ask the chemistry and analytical owners to reconcile the declared basis, then check the specification and product composition. Do not make the names identical by deleting the distinction.
Use S.3 characterization to support the identity and P.2 development for the consequences of relevant properties. Keep an uncertain assignment visible in all affected accounts until it is resolved.
Your preparation checklist
0/3 checkedUse this to track your review in this visit. Checks are not saved and do not establish regulatory compliance.
Frequently asked questions
Is S.1 a substitute for structural characterization?
No. S.1 presents the identity and relevant properties. S.3.1 explains how characterization evidence supports the identity and addresses relevant uncertainties. Link the two so the description agrees with the evidence; attaching an attractive structure drawing does not establish its correctness.
Can a free-base property be used for a salt form?
Only with an appropriate scientific basis and clear explanation of what the value represents. Different forms and measurement conditions can affect the property. Identify the actual tested material and obtain the relevant assessment instead of silently copying a value into the salt description.
Are S.1.1, S.1.2 and S.1.3 separate electronic files here?
They are useful narrative topics in M4Q, but this displayed FDA eCTD v4.0 hierarchy places the general-information content under S.1. Confirm the publishing structure rather than treating every narrative subsection as a separate electronic node.
Sources and revisions
Requirements, source recommendations and editorial preparation advice have different roles. Review the scope and revision of the source you use.
Guidance
ICH M4Q(R1): CTD Quality ↗Step 4, September 12, 2002; Module 3, printed pages 5–18. Organization/content guidance, not a universal list of required studies. Checked September 22, 2026. Guide-specific passages: 3.2.S.1.1–3.2.S.1.3, printed pages 5–6.
Technical specification
FDA eCTD v4.0 headings and hierarchy ↗Version 2.2, February 2025, printed pages 5–6; electronic placement only. Checked September 22, 2026.
Technical specification · placement only
FDA eCTD v4.0 comprehensive hierarchy ↗Version 2.2, February 2025. Section 3.2.S.1. A heading identifies placement, not mandatory applicability.