INTRODUCTION: BACKGROUND INFORMATION AND SCIENTIFIC RATIONALE The increased incidence of
antibiotic resistant 'superbugs' has amplified the use of broad spectrum antibiotics
worldwide. An unintended consequence of antimicrobial treatment is disruption of
gastrointestinal microbiota, resulting in susceptibility to opportunistic pathogens, such as
Clostridium difficile (C. difficile).
C. difficile is a gram-positive, spore-forming, anaerobic bacterium that causes hospital and
community-acquired enteric infections resulting in C. difficile-associated diarrhea, pseudo
membranous colitis, colitis and death.
Clostridium difficile infection (CDI) remains the predominant cause of health care
-associated infectious diarrhea, centered mainly in hospitals but also in the community at a
rate of ~100/100,000 population and affecting the elderly disproportionately. Antimicrobial
damage to the intestinal microbiome combined with the acquisition of spores of C. difficile
is the main cause of pathogenesis. CDI is endemic in hospitals, and although infection
control measures have reduced nosocomial rates of CDI in Canada over the past 5 years,
community cases now appear to be more apparent .Treatment of CDI utilizes alternate
antimicrobials directed at the pathogen, mainly metronidazole, vancomycin, or fidaxomicin
given for a recommended 10-14 days. While the majority respond to antibiotic treatment,
subsequent recurrences of CDI are observed in 25-40% of patients. Recurrences of CDI are
retreated with the same antibiotics and due to the non-selective spectrum of activity of
metronidazole and vancomycin, recurrences are increasing in probabilities for subsequent
recurrences. Fidaxomicin is relatively more selective and its use is associated with reduced
recurrences, but the high cost of fidaxomicin has restricted the usage.
C. difficile infection is a serious diarrheal illness associated with substantial morbidity
and mortality and is responsible for hospital and community-acquired diarrhea, pseudo
membranous colitis colitis and death..
ImmuniMed Inc. has developed an oral Immunotherapy using egg-derived anti- C. difficile
polyclonal antibodies (IM-01), that directly targets the virulence factors of C. difficile.
IM-01 is produced from chicken eggs following the immunization of laying hens with C.
difficile virulent antigens, C. difficile toxin A, toxin B, C. difficile whole cells and C.
difficile spores. IM-01 is in the form of spray-dried whole egg powder (yolk plus egg white
containing ovalbumin) and is very stable for functional activity. Upon reconstitution, IM-01
is administered orally, which allows it to reach to the intestinal lumen, where C. difficile
toxins exert their toxic effects. In addition, IM-01 antibodies bind to C. difficile toxins
and spores and neutralize their biological activities in vitro.
The use of polyclonal antibodies derived from chicken eggs (IgY) to confer passive immunity
has gained attention as a novel strategy for oral immunotherapy as an alternative to
antibiotics for treatment of intestinal pathogens which cause diarrhea in animals and humans
including, enterotoxigenic E. coli, Salmonella spp, and both bovine and human rotaviruses.
Compared with mammalian antibodies (IgG), chicken egg-derived antibodies (IgY) have high
antigen-specificity and avidity, react more rapidly to the same antigens and differ from
mammalian antibodies (IgG) in both structural and immunological properties.. Compared to IgG,
IgY is more stable in gut at pH 3.5 -11 and better tolerates enzymatic degradation by trypsin
and chymotrypsin; the stability of IgY against pepsin is pH-dependent.
Immunimed has determined that IgY polyclonal antibodies-specific to E. coli in egg powder
containing albumin, are functionally stable when stored at 2-8°C for over 10 years.
This makes IM-01 antibodies attractive for oral immunotherapy since eggs are normal dietary
components, with no known toxic side effects. The IM-01 antibodies are shown to bind with C.
difficile toxins and spores as well as to neutralize their biological activities in vitro.
Compared with active vaccination, passive immunotherapy using IM-01 egg-derived polyclonal
anti-C. difficile antibodies has advantages including: (i) rapid and local onset of action,
(ii) highly specific activity, (iii) applicability to a broader range of patients from
children to adults including immunocompromised patients, (iv) strategically can be applied
for a specific event when it occurs, in contrast to a vaccination model where large
populations need to be treated in advance and sustain active antibodies for long-durations,
and (v) is a normal part of human diet.
In a published literature, hamsters treated orally with C. difficile anti-toxin A and
anti-toxin B neutralizing egg-derived polyclonal antibodies were protected following C.
difficile challenge. Also, hamsters treated with egg-derived antibodies did not develop
relapsing disease months after the treatment with antibodies. .
Furthermore, egg-derived polyclonal antibodies have several advantages over the monoclonal
antibodies (MAbs), since MAbs are generally specific for single epitope, when polyclonal
antibodies - a new class of biopharmaceuticals, that have higher affinities for multiple
target antigens and can recognize multiple epitopes resulting in superior potency; since they
can recognize multiple toxin epitopes as it is relevant to polymorphism of the toxin A and
toxin B genes in C. difficile.
A piglet study was performed to demonstrate the safety and therapeutic effect of egg-derived
polyclonal antibodies -specific to E. coli K-88, in farm animals. It has been established
that E. coli K88 that cause diarrhea in piglets by colonizing in the lower GI tract of
piglets improve their growth performance following treatment with E. coli K-88-specific
antibodies orally.Furthermore, the highest body weight gain was achieved in pigs which were
fed with the highest dosage of E. coli K-88 antibodies (4kg/1000 kg of nursery diet) compared
to the lowest antibody dosage (1kg /1000 kg of nursery diet).
It was concluded that feeding of piglets with egg-derived polyclonal antibodies-specific to
E. coli K-88 results in significantly improved growth performance in an antibody
dose-dependent manner. The manufacturing process for egg-derived polyclonal antibodies
targeted to enterotoxigenic E. coli has been approved and validated by the Canadian Center
for Veterinary Biologics.
In conclusion oral Immunotherapy using polyclonal antibodies is considered to have a high
safety profile with a low likelihood of adverse effects. If proven to be effective as an
anti-infective approach, antibiotic selection pressure could be reduced, a key strategy to
limit antibiotic resistance in C. difficile infections.
IM-01 is spray-dried egg powder product containing polyclonal antibodies -specific to C.
difficile toxins A and toxin B, plus antibodies to C, difficile spores. A 20g/day dosage of
IM-01 was selected based on a pre-clinical animal study data, using piglets to treat with C.
difficile enteritis.disease with 0.6g of IM-01 orally daily for 4 days.
Under compassionate grounds, patients with confirmed CDI clinical diagnosis with unformed
diarrheal stools, abdominal cramps and a positive stool test for the presence of toxins
and/or C. difficile in culture, 106 patients (ages: 11-93 years) were enrolled for the
clinical study. All patients signed informed consent forms to participate in the study. The
amount of IM-01 antibody powder product (10g or 20g) orally administered daily by each
patient with 150 mL of milk and followed for up to 6-week period following IM-01
immunotherapy. Seventy six patients received an oral dose of 20 g of IM-01 and 30 patients
received 10 g of IM-01 powder daily for 10 consecutive days, as drinkable therapy with milk
or chocolate milk. The primary endpoint of the study was to eradicate C. difficile in stool
samples.
Of the 106 patients treated with IM-01 therapy,101 patients showed significant improvement of
clinical symptoms with negative stool test results for CDI.Five patients showed reduced
clinical symptoms during IM-01 treatment period. No recurrence was observed with IM-01
therapy during the follow up period. No safety concerns were reported.
Standard of care (SOC) antibiotics for the treatment of CDI have observed responses to
treatment i.e. resolution of diarrhea and ancillary symptoms/signs in 72-88% of subjects, and
for those subjects who do achieve resolution of CDI, 16-24% experience a recurrence of CDI
within an 8 week follow up. Non-responders are treated with higher dosages of vancomycin. day
interval. A post-treatment minimal follow up period of 30 days has been used in recent RCTs
of antimicrobials. Other trials have used several time points i.e 8 weeks or 12 weeks post
-treatment. Therefore, in absence of a standard of care control arm, the foregoing response
rates for resolution of CDI symptoms (80%), and a recurrence rate of 20% will be used for as
a response template for this study. In the absence of randomization of subjects to an
antibiotic treatment control group,