Analytical methods
Methods recorded against at least one compound, with the purpose stated by the source. Numeric acceptance criteria appear only where a regulatory or pharmacopoeial document publishes them. For several compounds every limit is withheld as commercially confidential, and none is stated here rather than estimated.
Absorbance ratio A260/A340
Discrimination of the oxidised from the reduced form. The oxidised form has essentially no absorbance at 340 nm, so a rising 340 nm signal indicates reduced-form contamination
Absorbance ratios A250/A260 and A280/A260
Identity and purity check
A250/A260 0.83 ± 0.03; A280/A260 0.21 ± 0.02, at pH 7.5
CE-ICP-MS/MS
Speciation-preserving copper determination, monitoring the copper-63 signal to distinguish encapsulated from free complex without prior separation
Cell-based bioassay
Potency, by indirect measurement of adenylate cyclase activation of the cloned human GLP-1 receptor. Limited to one batch in ten in routine active-substance testing; not a finished-product release test
Functional identity on the drug substance; the third orthogonal identity test
CG-MALS
Composition gradient multi-angle light scattering, used in structural characterisation to probe oligomeric state and self-association
Chiral GC-MS
Amino acid configuration in the characterisation package; the racemisation control for a synthetic peptide
Enzymatic cycling assay with selective acid or alkali destruction
Ultra-sensitive quantitation, exploiting the opposite pH lability of the oxidised and reduced forms to resolve them
EPR spectroscopy
Confirmation of the nitrogen donor set. Reported parallel hyperfine coupling 19.5 millitesla and g-parallel 2.21, with seven-line nitrogen superhyperfine splitting indicating three coordinated nitrogen atoms
Far-UV and near-UV circular dichroism, FT-IR, NMR
Higher-order and secondary structure characterisation; secondary structure recorded as predominantly alpha-helical under native conditions
GC
Residual solvents on the drug substance, relevant given the solid-phase synthesis route
High-resolution LC-MS
Identification of the components present in isolated major impurity peaks from the active substance
HILIC-MS/MS
Absolute quantitation across the metabolite panel without ion-pairing reagents, resolving the oxidised and reduced forms of both the dinucleotide and its phosphate
ICP-MS
Elemental impurities. Batch data showed no relevant elemental impurity above 30 per cent of its permitted daily exposure, so no routine control was required under ICH Q3D
Element-specific copper quantification
Ion chromatography
Counter-ion and ionic species determination in structural characterisation
Ion-pair RP-HPLC with ultraviolet detection at 260 nm
Simultaneous separation of the oxidised and reduced forms from ADP-ribose, AMP, ADP, ATP, adenosine and other degradants
Karl Fischer titration
Water content of the oral tablet finished product
Nitrogen determination
Value assignment of the primary reference material, related to the theoretical nitrogen content and corrected for the sum of impurities by chromatography
No compendial drug-substance monograph
The FDA recorded that no United States Pharmacopeia or National Formulary monograph exists, and that searches of the British, European and Japanese pharmacopoeias returned none either. The United States Pharmacopeia currently lists NAD+ among ingredients prioritised for monograph development, under a call soliciting technical data and analytical methods. A USP reagent specification does exist, but a reagent specification is not a drug-substance monograph and the two should not be conflated
Nuclear magnetic resonance, infrared spectroscopy and mass spectrometry
The characterisation set recorded by the FDA for this substance. Note that in one published protocol NMR did not detect AMP, adenosine or ADP-ribose, which is relevant if it is proposed as an impurity method
Peptide mapping
Identity test on the finished product, alongside chromatographic retention
Primary-structure identity on both drug substance and finished product; the second of the orthogonal identity tests
RP-HPLC / RP-UHPLC
Assay, purity and related substances, and uniformity of dosage units. The assessment record concludes that main-peak content by this method is a reliable measure of bioactivity in both active substance and finished product
RP-HPLC with UV detection
Quantification in cosmetic formulation. Published conditions are partial: ODS C18 column, 0.2 per cent trifluoroacetic acid, detection at 220 nm. Column dimensions, gradient, flow rate and validation data are not published
RP-LC-MS
Purity by a second, orthogonal detection principle alongside ultraviolet detection
RP-LC-UV
Drug substance and finished product: identification by retention, assay, and purity. One of three orthogonal drug-substance identity tests
SE-HPLC
Control of aggregation and high molecular weight proteins
SEC
High molecular weight species on drug substance and finished product
Sterility, particulate matter, pH, osmolality (Ph. Eur.)
Finished-product release tests for a sterile parenteral solution
Ultraviolet absorbance at 260 nm
Content assay by molar absorptivity
A measured value of 17.4 x 10^3 L/mol/cm at 25 °C is published in the peer-reviewed literature, while the specification filed with the FDA states 18.0 ± 0.5 x 10^3. These conflict and the discrepancy should be resolved before either is adopted
UPLC-HRMS peptide mapping
Primary-structure confirmation and localisation of the fatty acid modification site, using Glu-C and chymotrypsin digests to achieve full sequence coverage
UV-Visible spectrophotometry
Complex-formation confirmation and speciation. The copper(II) d-d absorption band is reported at 606 nm by two independent groups, and shifts in this band track changes in coordination number
Water content, bacterial endotoxins, TAMC and TCYMC (Ph. Eur.)
Drug substance release tests by pharmacopoeial methods