Aphton Announces Results from Phase I Clinical Trial with Lewis Y Antibody IGN311 for Treatment of Epithelial Cancers

  Clinical Trial Demonstrates Favorable Safety Profile and Indicates
 Efficacy Against Disseminated Tumor Cells in Patients with Cancers of
                           Epithelial Origin

   Aphton Corporation (NASDAQ:APHT) announced today the positive
results from an open-label dose-escalating Phase I trial with IGN311,
a humanized monoclonal antibody targeting the Lewis Y tumor-associated
antigen.
   Lewis Y is a factor known to be over-expressed in up to 90% of
epithelial carcinomas, including breast, colon, gastric and pancreatic
cancers. IGN311 is being developed as a potential new therapy for the
treatment of Lewis Y positive tumors. In this Phase I trial, IGN311
demonstrated favorable safety and tolerability, and advantageous
pharmacokinetics with a serum half-life of more than 20 days. Data
from the trial also indicate efficacy of IGN311 against Lewis
Y-positive tumor cells circulating in peripheral blood: the number of
such cells was significantly decreased in those patients that
presented with detectable levels of such cells prior to first
infusion.
   Twelve patients with epithelial cancers (breast, colorectal,
gastric and pancreatic) were enrolled. All patients received
intravenous infusions of IGN311, which was given in escalating doses,
of which 3 patients received 50mg, 3 patients received 100mg and the
remaining 6 patients received 200mg. IGN311 was administered on the
first and fifteenth days of the study. No adverse events related to
study medication were seen in the 50mg and 100mg cohort, and only one
adverse event (vomiting, nausea) was observed in the 200mg arm. The
antibody was generally well tolerated and hematological toxicities
were not observed. Complement dependent cytotoxicity (CDC), or the
capacity of the antibody to destroy tumor cells, was significantly
induced by IGN311 infusions, and was correlated with IGN311
concentration in blood.
   "We are quite pleased with both the favorable safety profile and
the antitumor activity demonstrated in this study. These results
provide us with confidence as we initiate new studies with the
compound," said Patrick Mooney, MD, President and Chief Executive
Officer of Aphton Corporation.

   About IGN311

   IGN311 is a humanized monoclonal antibody against the Lewis Y
carbohydrate antigen, a blood group related oligosaccharide. Lewis Y
is over-expressed in up to 90% of all epithelial cancers and its
expression on adult normal tissues is very restricted; hence IGN311
has the potential to target a broad range of carcinomas. IGN311 is
designed to exert clinical effects by destruction of tumor cells by
activation of effector functions and by selective growth inhibition
via functional receptors.

   Strategic Pipeline

   Aphton continues to focus its efforts on broadening and making
progress in its research and development pipeline. An important
component of our product portfolio is IGN101, a cancer vaccine
designed to induce an immune response against EpCAM positive tumor
cells, and IGN311. Aphton also has a diverse pipeline of pre-clinical
and clinical products including active and passive immunotherapies.
Aphton believes that immunotherapies may have certain advantages over
other targeted therapies by including specificity that may lead to
better efficacy and decreased toxicities for patients.

   About Aphton

   Aphton Corporation, headquartered in Philadelphia, Pennsylvania is
a clinical stage biopharmaceutical company focused on developing
targeted immunotherapies for cancer. Aphton's products seek to empower
the body's own immune system to fight disease. Through the acquisition
of Igeneon AG in March 2005, Aphton acquired late-stage products,
IGN101, a cancer vaccine designed to induce an immune response against
EpCAM positive tumor cells, and IGN311, a fully humanized antibody
against the Lewis Y antigen. Aphton is currently seeking partners that
will support the further development of Insegia (G17DT immunogen), its
immunogen targeting the hormone gastrin. Aphton has strategic
alliances with sanofi-aventis for the development and
commercialization of Insegia related to cancers of the
gastrointestinal system and other cancers in North America and Europe;
Daiichi Pure Chemicals for the development, manufacturing and
commercialization of gastrin-related diagnostic kits; and Xoma for
treating gastrointestinal and other gastrin-sensitive cancers using
anti-gastrin monoclonal and other antibodies. For more information
about Aphton or its programs please visit Aphton's website at
http://www.aphton.com.

   Safe Harbor

   This press release includes forward-looking statements, including
statements about: (1) the development of IGN311 as a potential new
therapy for the treatment of Lewis Y positive tumors; (2) Aphton's
intent to enter into new studies with IGN311; (3) the potential of
IGN311 to target a broad range of carcinomas and exert clinical
effects by destruction of tumor cells; (4) Aphton's belief regarding
the strength of Igeneon's product portfolio and such portfolio's
ability to complement Aphton's product portfolio; (5) Aphton's intent
to broaden and progress its research and development pipeline; (6)
Aphton's belief that immunotherapies have certain advantages over
targeted therapies; and (7) Aphton's intent to continue to seek, and
its ability to find, a viable partner to financially support the
further development of Insegia. These forward-looking statements may
be affected by the risks and uncertainties inherent in the drug
development process and in Aphton's business. This information is
qualified in its entirety by cautionary statements and risk factor
disclosure contained in Aphton's Securities and Exchange Commission
filings, including Aphton's report on Form 10-K filed with the
Commission on March 16, 2005. Aphton wishes to caution readers that
certain important factors may have affected and could in the future
affect Aphton's beliefs and expectations and could cause the actual
results to differ materially from those expressed in any
forward-looking statement made by or on behalf of Aphton. These risk
factors include, but are not limited to: (1) Aphton's ability to fund
the further development of its research and development programs; (2)
Aphton's ability to successfully identify and consummate opportunities
to broaden and progress its research and development pipeline;, (3)
scientific developments regarding immunotherapies; (4) Aphton's
ability to successfully integrate Igeneon's operations and product
portfolio with Aphton's operations and product portfolio; (5) the
actual design, results and timing of preclinical and clinical studies
for Aphton's products and product candidates; (6) the ability of
Aphton to develop and initiate additional clinical trials of IGN 311
and the future results of IGN 311 in the subsequent clinical trials.