What GMP covers, and what it does not
GMP is a system for making product consistently and being able to show it, not a certificate attached to a molecule. It governs premises and equipment, qualification of materials and suppliers, written procedures, training, in-process control, release testing against a specification, and record retention. It does not by itself say what the specification should be. That is set by the programme and its regulatory pathway, and it is why a specification discussion has to happen before a GMP batch is planned.
Specification and release testing
A peptide API specification typically covers appearance, identity by mass spectrometry and often by amino acid analysis, purity and individual impurities by HPLC, peptide content, water content by Karl Fischer titration, residual solvents by gas chromatography, counter-ion content, and where relevant bioburden, endotoxin and sterility. Each parameter needs a method, an acceptance criterion and a justification for both. Deciding this list is part of the project rather than a standard form.
Analytical method validation
Methods used to release material are validated for the characteristics they are relied on for: specificity, linearity, range, accuracy, precision, detection and quantitation limits, and robustness. A purity method that cannot separate a known related substance from the main peak is not fit for release regardless of how precise it is, so the impurity profile of the actual process drives what the method has to resolve.
Stability and storage
Stability studies under ICH Q1A conditions establish how long material meets its specification and under what storage conditions. For lyophilised peptides the parameters that usually move first are water content, purity and, where a sequence contains susceptible residues, specific degradation products such as oxidised methionine or deamidated asparagine. Study design and time points are agreed with the programme's requirements in view.
Documentation package
What accompanies a GMP batch is agreed in advance and typically includes the certificate of analysis, executed batch record summary, analytical raw data, method validation reports where applicable, and a statement of the materials used. Support for regulatory filings, including drug master file arrangements, is discussed per programme.