Biomedical Engineering Reference
In-Depth Information
development studies and the process capabilities. In cases where there is limited prior
product knowledge, specifications can be based on process capability data.
4.2 EXAMPLES OF CRITICALITY DETERMINATION
To illustrate the process by which the criticalities of product quality attributes can be
determined, two examples are provided here: glycosylation and deamidation. These
criticality determinations are described primarily for the anti-RSVmonoclonal antibody
motavizumab; however, relevant information for palivizumab is also included where
appropriate. Both palivizumab and motavizumab target the F protein of RSV, and
the molecules have been developed as prophylactics for prevention of RSV infection in
the primary population of premature infants. Motavizumab is the “next generation”
molecule developed through directed genetic engineering of the palivizumabmolecule to
achieve greater affinity for the target antigen [5]. Thus, motavizumab and palivizumab
have the same mechanism of action, biological activity, and quality attributes, while
differingby13aminoacids. For these reasons, informationforbothmolecules iscombined
to create a cumulative prior product knowledge and context for criticality determinations.
4.2.1 Case Study 1: Glycosylation
Prior Product Knowledge
L
ABORATORY
S
TUDIES
. Mammalian IgG1molecules generally have a conserved site
of N-linked glycosylation in C
H
2 domain of the Fc region of the heavy chains [6]. For
motavizumab, Asn-300 on the heavy chain is the only consensus site for N-glycosylation
and its occupancy was confirmed by peptide mapping with LC-MS.
The oligosaccharide structures of motavizumab are commonly found inmonoclonal
antibodies derived from NS0 mouse myeloma cell line [6-8]. An oligosaccharide
profiling method [9, 10] was used to identify the labeled oligosaccharide structures by
using MS or tandem MS. The predominant glycoforms (approximately 80%) are
fucosylated biantennary complex-type oligosaccharides either with no terminal galac-
tose residues (G0) or with monogalactosylated (G1) and digalactosylated forms (G2)
(Figs. 4.5 and 4.6).
The minor complex-type glycoforms are truncated G0 and G1 without Fuc or
GlcNAc, sialylated G1 and G2 containing N-glycolylneuraminic acid (NGNA), and G1
and G2 with murine Gal-
-1,3-Gal linkages (Fig. 4.5).
Most humans have circulating IgG antibodies directed against Gal-
a
-1,3-Gal
moieties exposed to glycoproteins [11]. A recent report [12] proposes that the presence
in patients of predose IgE directed against Gal-
a
a
-1,3-Gal may lead to anaphylaxis
following administration of cetuximab. While this report raises safety concerns for any
protein therapeutic that contains Gal-
-1,3-Gal linkages, we believe the risk is minimal
for palivizumab and motavizumab because (1) palivizumab has a very low immunoge-
nicity (less than 1% in over 4 million doses given), indicating that the small amount of
Gal-
a
-1,3-Gal glycoforms present is not likely to induce an antigalactosyl immunogenic
response; (2) Gal-
a
a
-1,3-Gal glycoforms of palivizumab and motavizumab are contained
