X-Message-Number: 27632
Date: Sat, 18 Feb 2006 10:24:00 -0800 (PST)
From: Doug Skrecky <>
Subject: sorbitol aids in high temperature storage

[Sorbitol's resistance to crystalization may offer an advantage
in freeze-drying.]

J Pharm Sci. 2005 Jul;94(7):1445-55.
Effect of sorbitol and residual moisture on the stability of
lyophilized antibodies: Implications for the mechanism of protein
stabilization in the solid state.
  PURPOSE: To investigate the effect of plasticizers on the
stability of protein formulations in the solid state and to apply
these results to a study of mechanisms of protein stabilization
by sugars in the solid sate. METHODS: The IgG1 antibody was
formulated with either sucrose or trehalose alone or a mixture of
sorbitol with sucrose or trehalose. After lyophilization, the
pure protein and sucrose formulations were equilibrated at
different relative humidities giving residual moistures from less
than 1% to 5% for sucrose systems and up to 17% for pure protein
systems. All the samples were stored at 50 degrees C for up to1
month and at 40 and 25 degrees C for up to 6 months. Aggregation
and chemical degradation were monitored by size exclusion
chromatography (SEC) and ion exchange chromatography (IEX),
respectively. The secondary structure was characterized by FTIR
using second derivative analysis of Amide I region. Structural
relaxation times, tau, an indication of molecular mobility in the
glassy matrix, were characterized using the thermal activity monitor
(TAM). The tau values of the recombinant human monoclonal antibody
(rhuMab) formulation with various water contents were also measured
in this study and compared with stability data taken from the
literature (Breen ED, Curley JG, Overcashier DE, Hsu CC, Shire SJ,
2001, Pharm Res 18:1345-1353). RESULTS: The structural relaxation
time, tau, decreased sharply with increasing water content. However,
the stability data suggest a minimum in degradation rate at 2%-3%
water content. Addition of a small amount of sorbitol to a
sucrose-based formulation resulted in greater retention of native
structure, smaller relaxation time, but improved stability. However,
with the trehalose-based formulations, addition of sorbitol had no
effect on protein structure (FTIR), but the decrease in relaxation
time and the improvement in stability were qualitatively similar to
the corresponding data obtained with the sucrose-based formulation.
CONCLUSION: Glass dynamics as measured by tau could not explain the
stability results. Stability correlated best with the preservation
of native structure for sucrose-based formulations, but with the
trehalose-based formulation, neither structural relaxation time nor
extent of native structure was predictive of stability. However, it
is possible that the beta-relaxations rather than the
alpha-relaxation (i.e., the tau we measured) is critical to the
stability. Plasticizers like glycerol may decrease tau for
"alpha-motion" but increase tau for "beta-motion" and stabilize
proteins (Cicerone MT, Tellington A, Trost L, Sokolov A, 2003,
BioProcess Inter 1:1-9).

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