RECOMBINANT ALBUMIN FUSION PROTEINS - Fusion Protein Technologies for Biopharmaceuticals: Applications and Challenges - page 162

10.3.1 Albumin Fusion Proteins in Late-Stage
Development

The safety and efficacy of alb-IFN have been evaluated in
two Phase III trials in patients with genotype 1 (ACHIEVE
1) or genotype 2/3 (ACHIEVE 2/3) CHC [27,55,56]. In the
ACHIEVE 1 trial, 1331 IFN- a -naive patients were random-
ized to alb-IFN (900 or 1200 m g every 2 weeks) or PEG-
IFN- a -2a (180 m g weekly) [27]. On the basis of an intent-to-
treat analysis, alb-IFN met its primary efficacy endpoint of
noninferiority to PEG-IFN- a -2a with 48.2% of patients in
the 900 m g alb-IFN arm achieving SVR compared to 51.0%
of those in the PEG- IFN- a -2a arm. Adverse events were
generally similar between the two arms and to those typi-
cally reported for IFN- a . However, the 1200 m g dose of alb-
IFN was associated with a higher rate of serious pulmonary
adverse events and treatment discontinuations. The applica-
tion for a marketing authorization for the 1200- m g dose of
alb-IFN was recently withdrawn by the sponsor because of
the regulatory feedback on the relative risk-to-benefit ratio
[57]. Consequently, all patients in the ACHIEVE 1 trial
receiving alb-IFN 1200 m g were switched to 900 m g given
every 2 weeks [27].

10.3.1.1 Interferon-a Interferon- a (IFN- a ) is a cytokine
with antiviral, immunomodulatory, and antiproliferative
properties. It is used to treat viral infections, such as hepatitis
B and C, and certain malignancies, such as melanoma. The
half-life of IFN- a in humans, however, is 2-3 h, so treatment
is often given daily or three times weekly [9]. Two versions
of IFN- a are available in which polyethylene glycol (PEG)
is covalently attached to IFN- a (PEG-IFN- a -2a and PEG-
IFN- a -2b). PEGylation improves the pharmacokinetics of
IFN- a , resulting in a prolonged half-life and allowing for
weekly dosing [48,49]. Nevertheless, 45% of chronic

hepatitis C (CHC) patients do not achieve a sustained
virological response (SVR) with these agents [50].
Albinterferon- a -2b (alb-IFN), or Albuferon 1 ,sa
recombinant albumin fusion protein that combines the anti-
viral activity of IFN- a with the prolonged half-life of
albumin. The fusion protein has a molecular mass of

85.7 kDa and is formed by fusing the C-terminus of
rHA to the N-terminus of recombinant human IFN- a
[51]. It is produced in a Saccharomyces cerevisiae expres-
sion system [52], and purified using a combination of anion,
cation, and semi-affinity chromatography [51]. In monkeys,
alb-IFN demonstrated improved pharmacokinetics, includ-
ing prolonged half-life, reduced clearance, and increased
stability, compared to IFN- a [51]. These improvements led
to better pharmacodynamics, based on expression levels of
2 0 ,5 0 -oligoadenylate synthetase (OAS), a biomarker of IFN-
a activity, and remained elevated for up to 10 days after a
single injection. In serum samples, alb-IFN was shown to
maintain antiviral activity for up to 8 days after injection
compared to 5 days for PEG-IFN- a -2b and 1 day for IFN- a .
The half-life of alb-IFN (93 h) was over twofold greater than
the mean half-life of PEG-IFN- a -2b (40 h) and around 18-
fold greater than that of IFN- a (5 h). Allometric scaling
predicted a half-life in humans of 90-288 h, thereby sup-
porting dosing every 2-4 weeks.
In humans with IFN- a -naive, genotype 1 CHC, the mean
absorption half-life of alb-IFN was 23-31 h after sub-
cutaneous administration [26]. The maximum concentration
increased linearly with the dose and was reached at a mean
of 65-87 h after dosing. Fusion to albumin extended the half-
life of IFN- a -2a from 4 to 141 h (

10.3.1.2 Glucagon-Like Peptide-1 Glucagon-like pep-
tide 1 (GLP-1) is an incretin hormone secreted in the
intestines that stimulates insulin secretion by binding to
GLP-1 receptors found on beta cells and various components
of the central and peripheral nervous systems [22]. GLP-1
inhibits gastric emptying, regulates appetite and food intake,
enhances glucose disposal, and improves endothelial dys-
function. Despite these potent activities, the use of GLP-1 in
the treatment of diabetes has been hindered by its rapid
degradation in circulation by dipeptidyl peptidase-4. Fusion
proteins have been developed that combine albumin with
various GLP-1 analogs and mimetics, and several Phase III
trials are underway to evaluate these fusion proteins as
monotherapy or in combination with other medications
for diabetes [22].
Albiglutide (formerly known as albugon) is an albumin
fusion protein generated by fusing the gene sequence encod-
ing a dimer of recombinant dipeptidyl-peptidase IV resistant
GLP-1 analog with the open reading frame of rHA [24].
Studies conducted in vivo indicate that albiglutide activates
GLP-1 receptor-dependent central and peripheral pathways
that regulate energy intake and glucose homeostasis. These
results suggest that the altered molecular configuration that
arises when GLP-1 is fused to rHA does not eliminate its
ability to recognize and activate GLP-1 receptors. Phase II
clinical trial results indicated improved fasting and post-
prandial plasma glucose levels in diabetes patients and a
systemically improved half-life of about 5 days with
albiglutide compared to around 5min for wild-type
GLP-1 [24,58].
Another dipeptidyl-peptidase IV resistant GLP-1 fusion
protein was developed by attaching a lysine residue at the N-
terminus of GLP-1 (termed KGLP-1) with albumin fused to

6 days), which was also
approximately twofold greater than published results for
PEG-IFN- a -2a (72 h) [48,53] and around fourfold greater
than that of PEG-IFN- a -2b (40 h) [54]. Similar results were
noted in 119 CHC patients (mostly with genotype 1) who
had previously received IFN- a [50]. The improved pharma-
cokinetics compared to conventional IFN- a therapies led to
improvements in pharmacodynamic properties: expression
of the gene OAS1 was maintained for more than 28 days after
a single injection of alb-IFN.