CLASSIC IMMUNOTOXINS WITH PLANT OR MICROBIAL TOXINS - Fusion Protein Technologies for Biopharmaceuticals: Applications and Challenges - page 275

malignant glioma were intratumorally treated with high-
flow interstitial microinfusion of transferrin-CRM107 by
convection-enhanced delivery (CED), which permitted
direct drug delivery to the brain tumor interstitum. Of 15
eligible patients, 9 had objective responses (2 CR and 7 PR)
[139]. In a Phase II trial, 44 patients received 40 mL of
0.67 m g/mL over 4-5 days by CED. Of 34 patients evaluated
for efficacy, there were 5 CR and 7 PR (overall response rate:
35.3%). Owing to lack of objective efficacy in a Phase III
trial for comparison with best standard treatment, further
clinical development of transferrin-CRM107 was discon-
tinued [140]. Detailed clinical data have not been published.
IL13-PE38QQR is composed of interleukin-13 fused to
PE38QQR. IL13-PE38QQR was administered by CED to
recurrent glioblastoma multiforme tumors for up to 6 days.
Nine patients (17.6%) and seven patients (13.7%) had a
prolonged progression-free survival beyond one and two
years, respectively [141]. IL13-PE38QQR treatment showed
similar overall survival and safety profiles as compared to
Gliadel wafer treatment in a Phase III trial for glioblastoma
patients [142].
Anti-CD5 IgG (H65)-RTA is a chemical conjugate of
anti-CD5 antibody (H65) and ricin A chain. In a Phase I for
CTCL, patients received intravenous doses of 200-
330 m g/kg daily for 10 days. There were 4 PRs out of 14
patients. No CR was observed in this trial [78]. In a Phase I/II
for patients with GVHD in the liver, gut, or skin, anti-CD5
IgG (H65)-RTA was administered 14 daily intravenous
infusions of 50-330 m g/kg. There were 9 CR and 7 PR
out of 32 evaluated patients. Anti-CD5 IgG (H65)-RTA
treatment depleted 80% of CD5

The presence of target antigens on normal tissues can lead
to significant toxicities. LMB-1, LMB-7, LMB-9, and BR96
(sFv)-PE40 are PE immunotoxins that bind the Lewis Y
antigen on many carcinomas. The Lewis Y antigen is also
expressed on normal gastrointestinal (GI) epithelium and
within the pancreas [157]. Dose-limiting toxicity was GI
toxicity in these trials except for a Phase I trial of LMB-1.
260F9-rRA is a ricin immunotoxin that binds a 55-kDa
antigen expressed on breast carcinomas and normal Schwann
cells [158]. Two Phase I clinical trials of 250F9-rRA have
been stopped without clinical responses after the occurrence
of reversible but prolonged peripheral neutropathies [91,158].
Clinical trials with OVB3-PE (anti-ovarian cancer antigen
PE immunotoxin) and 454A12-rA (antitransferrin receptor
ricin immunotoxin) were discontinued after CNS toxicity
[159,160]. OVB3-PE and 454A12-rA cross-react with a
normal antigen on the pons and transferrin receptors
on normal brain capillaries, respectively. DAB 389 EGF and
erb-38 react with EGFR and Her2 receptors present on
normal hepatocytes, resulting in dose-limiting liver injury
[113,124,161]. DT 388 GMCSF reacts with normal liver
macrophages, Kupffer cells. Subsequent cytokine release
triggers dose-limiting hepatocyte damage [162]. Transferrin-
CRM107 produces cerebral edema because of cross-
reactivity with trasferrin receptors on normal brain capillaries
and subsequent damage [139]. HUS (hemolytic uremic syn-
drome) seems to be a dose-limiting toxicity restricted toCD22
and CD19 targeting immunotoxins [133,134,163,164],
because other immunotoxins do not cause HUS.

blood lymphocytes
[143]. Anti-CD5 IgG (H65)-RTA was further evaluated in
a Phase III clinical trial. Combination therapy of anti-CD5
IgG (H65)-RTA with glucocorticoids showed no long-term
clinical benefits in GVHD patients [144].
Overall response rates

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18.5 CHALLENGES AND PERSPECTIVE
OF CLASSIC IMMUNOTOXINS

18.5.1 Adverse Events

10% were observed in trials of
NBI-3001 [121], Xomazyme-791 [145], TGF a -PE40 [146],
scFv(FRP5)-ETA [147], XMMME-001-RTA [88], SPV-
T3a-dgA/WT1-dgA [148], anti-B4-bR [82,149], IgG-
HD37-dgA [150], B43-PAP [151], Combotox [152], IgG-
FRB4-dgA [79,153,154], RFT5-SMPT-dgA [86], Ki-4.dgA
[155], and N901-bRicin [156].
Common toxicities observed with different immunotoxin
trials are (1) transient vascular leak syndrome (VLS)
consisting of edema, hypoalbuminemia, weight gain, and
dyspnea; (2) transient hepatotoxicity with elevated trans-
aminases; and (3) infusion-related hypersensitivity with
fever, chills, nausea, vomiting, myalgias, arthralgias, and
asthenia. These common toxicities may be due to binding of
the toxin moieties to normal tissues. Reaction of immuno-
toxins with macrophages, lymphocytes, or endothelium may
lead to cytokine release with consequent infusion-related
hypersensitivity.

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As discussed above, three major adverse events (vascular
leak syndrome (VLS), infusion-related hypersensitivity, and
liver toxicity) in clinical trials were commonly observed in
all classic immunotoxin trials. Acute infusion-related hyper-
sensitivity is characterized by fever, chills, nausea, vomiting,
myalgias, arthralgias, hypotension, dyspnea, chest pain, and
back pain whose symptoms occur within 24 h of drug
infusion. Acute infusion-related hypersensitivity occurred
in up to 80% of patients receiving monoclonal antibody or
other protein-based therapies [166]. Acute hypersensitivity
events are common in most of protein-based therapies. Liver
toxicity may be related to nonspecific uptake of imunotoxins
by Kupffer cells. The major dose-limiting toxicity of classic
immunotoxin therapies is VLS. VLS is characterized by
hypotension, peripheral edema, and hypoalbuminemia. VLS
in severe form causes pulmonary and cardiovascular failure.
Symptoms are variable among patients and the causes