Isolation and identification of peptide degradation products of heat stressed pramlintide injection drug product.
OBJECTIVE
This report summarizes the identification of nine deamidation and four hydrolysis products from a sample of pramlintide injection final drug product that was subjected to stress at 40 degrees C for 45 days.


METHODS
The pramlintide degradation products were isolated by strong cation exchange HPLC followed by reversed-phase HPLC. Subsequent to isolation, the molecular weight of each component was determined by liquid chromatography-mass spectrometry (LC/MS). Further characterization was accomplished by amino acid sequence analysis and/ or enzymatic (thermolysin) digestion followed by LC/MS and sequence analysis.


RESULTS
The isolated products were identified as [iso-Asp21]-pramlintide, [iso-Asp3]-pramlintide, and [iso-Asp22]-pramlintide, the deamidation products of pramlintide with rearrangement at Asn21, Asn3, and Asn22, respectively. Also found were [Asp/iso-Asp14]-pramlintide, and [Asp/iso-Asp35]-pramlintide, the deamidation products at Asn14, and Asn35, and [Asp21]-pramlintide together with [Asp22]-pramlintide. For the deamidations at the 14th and 35th residues, it could not be determined whether the substance corresponded to the Asp or the iso-Asp product. The [Asp21] and [Asp22] products could not be separated from each other chromatographically but were both identified in a single fraction. Two minor degradation products were also identified as deamidated species. However, the sites of deamidation remain unknown. Also identified were [1-18]-pramlintide, [1-19]-pramlintide, [19-37]-pramlintide, and [20-37]-pramlintide, the products of hydrolytic peptide backbone cleavage at amino acids His18/Ser19 and Ser19/Ser20, respectively. One other product was isolated and tentatively identified as a cyclic imide intermediate preceeding deamidation.


CONCLUSIONS
The primary mode of thermally induced degradation for this peptide is deamidation. A second degradation mechanism is peptide backbone hydrolysis.
Hekman
C
C
Amylin Pharmaceuticals, Inc., San Diego, California 92121, USA. chekman@amylin.com
DeMond
W
W
Dixit
T
T
Mauch
S
S
Nuechterlein
M
M
Stepanenko
A
A
Williams
J D
JD
Ye
M
M
D000595:Amino Acid Sequence; D000682:Amyloid / Q000032:analysis / Q000737:chemistry*; D002852:Chromatography, Ion Exchange; D006358:Hot Temperature; D006868:Hydrolysis; D007004:Hypoglycemic Agents / Q000032:analysis / Q000737:chemistry*; D058228:Islet Amyloid Polypeptide; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry* / Q000302:isolation & purification; D013820:Thermolysin
D000682:Amyloid; D007004:Hypoglycemic Agents; D058228:Islet Amyloid Polypeptide; D010446:Peptide Fragments; C105254:pramlintide; D013820:Thermolysin