Biomedical Engineering Reference
In-Depth Information
show that the oligosaccharide profile is consistent and reproducible at different scales
(500 and 12,000 L) and different manufacturing sites.
C
RITICALITY
D
ETERMINATION
. Severity-Impact on Safety: The major glycoforms
shown in Fig. 4.5 are naturally occurring in humans and have no known safety risks.
Furthermore, all glycoforms were present in all nonclinical and clinical studies, and an
acceptable safety profile was observed.
Severity-Impact on Efficacy: Palivizumab and motavizumab are humanized mono-
clonal antibodies directed to an epitope in the A antigenic site of the F fusion protein of
RSV. The sequences of motavizumab and palivizumab differ by 13 amino acids. The
mechanism of action for motavizumab is the same as palivizumab. The Fab portion
contains the viral binding elements, and the Fc portion contains an N-linked oligosac-
charide chain attached to a single site on the heavy chain (Asn-300). The mechanism of
action is through binding to the RSV F protein (specific neutralizing epitope) on the
surface of the virion. The RSV F protein mediates an essential step of the infection
process by enabling the fusion of the virus and host cell membranes, thus facilitating
entry of the virus into the cell. Binding to the F protein blocks the essential site or sites for
fusion to occur, thereby preventing infection of the cell by the virus.
The Fab-mediated mechanism of action for motavizumab is considerably simpler
than that for other monoclonal antibodies (e.g., Herceptin
or Rituxan
) because these
require Fc effector function-dependent activities, such as antibody-dependent cellular
cytotoxicity or complement-dependent cytotoxicity [26-28]. Fc effector functions can
be modulated by the glycosylation state [29] and consequently can affect the potency of
such antibody products. In contrast, RSV neutralizing activity is not mediated by Fc
effector functions, and changes in motavizumab Fc glycosylation patterns do not affect
potency.
To evaluate the role of the N-linked oligosaccharide side chain on the biological
properties of motavizumab and palivizumab, both antibodies were enzymatically
remodeled to generate enriched G0, G2, and deglycosylated variants. All variants were
evaluated in in vitro bioactivity assays as well as in the cotton rat animal model. Results
for both antibodies support the conclusion that variations in the proportions of the major
glycoforms found on the oligosaccharide side chain do not impact their biological
properties. In addition, the results with palivizumab and motavizumab indicate that the
PK profiles in cotton rats are not influenced by a range of oligosaccharide proportions.
For human PK studies, any combination of oligosaccharide composition within the range
of 0-100% for all three glycoforms (G0, G1
Man-5, and G2) would result in a lot with
AUC no less than 80% of motavizumab drug product. Taken together, these observations
indicate that there is minimal risk to efficacy due to glycoforms proportions.
Likelihood: The manufacturing process consistently produces material that is well
within the range of the prior product knowledge (Fig. 4.15). Therefore, the likelihood of
occurrence is very low.
Conclusion: The criticality of glycosylation is shown in Fig. 4.19 and was deter-
mined by using the methodology previously described. On the basis of the data presented
in this section, there is minimal risk to safety or efficacy due to variation in oligosac-
charide proportions of motavizumab. Therefore, glycosylation is considered to be a
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