N E W S  R E L E A S E

             INTERIM GASTRIC CANCER IMPRESSIVE RESULTS PRESENTED AT
                        ASCO FROM APHTON PHASE II TRIAL

                           May 20, 2002, Orlando, FL.

Orlando, FL - Aphton Corporation (NASDAQ NMS: APHT)-At the annual meeting of the
American  Society of Oncology  (ASCO) in Orlando,  FL, on Sunday,  May 19, 2002,
investigators from the UCLA Jonnson  Comprehensive Cancer Center in Los Angeles,
CA and the MD  Anderson  Cancer  Center in  Houston,  Texas,  presented  further
impressive  interim  results  from a Phase II  clinical  trial  with  previously
untreated  patients  diagnosed with metastatic stomach cancer. The patients were
treated with Aphton's anti-gastrin immunogen (G17DT) and chemotherapy consisting
of cisplatin and 5FU.

Of the 36 reported  and  audited  evaluable  patients  (20% more  patients  than
previously reported), 19 had a partial tumor response (tumor shrinkage by 50% or
more) for an overall  response  rate of 53%,  the highest yet  reported for this
combination  therapy.  Of the balance,  11 patients had stable  disease (SD), so
that the combined  tumor  response rate and stable  disease was 84%. One patient
had a complete  response  (no  detectable  residual  tumor) and 18 had a partial
response. These results compare favorably with the only large, randomized, phase
III trial with cisplatin plus 5 FU/Leucovorin for patients with advanced gastric
cancer,  which  reported a tumor  response  rate of 20%.  Aphton's  anti-gastrin
targeted   immunotherapy  adds  a  biological  dimension  to  the  treatment  of
gastrointestinal cancers.

On Friday,  May 17, 2002, a special symposium was held by Aventis (AVE), a major
pharmaceutical  company and Aphton's strategic partner for treating cancers with
Aphton's G17DT.  Jaffer Ajani,  MD, of the MD Anderson Cancer Center in Houston,
Texas  and a leading  authority  worldwide  on  gastrointestinal  (GI)  cancers,
described  the  molecular  and  biological,  central role of gastrin and gastrin
receptors  in  the  development,   growth,   proliferation   and  metastasis  of
adenocarcinomas  of the GI  tract.  Noting  that  there is no  approved  therapy
currently  available and that  chemotherapy is considered only  palliative,  Dr.
Ajani  discussed the  inhibition of the growth and spread of these  cancers,  in
vitro, in vivo, and presented the above described audited interim results of the
clinical  trial with patients with  metastatic  stomach  cancer who were treated
with Aphton's G17DT and chemotherapy consisting of cisplatin and 5FU.

On Monday, May 20, 2002,  investigators  from the University of Nottingham,  UK,
and the Derbshire  Royal  Infirmary,  UK,  presented the results from a phase II
study with patients with histologically  proven stage IV gastric cancer who were
treated with Aphton's G17DT,  but with no chemotherapy  administered.  Of the 10
evaluable patients,  the
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median  survival  was 7.1 months,  which the  investigators  said  compared to a
median  survival  of 4.8 months in  previous  studies  for such stage IV gastric
cancer patients (a 48% median survival benefit).

Concurrently,  investigators from the University of Nottingham presented results
from in vitro and in vivo  pancreatic  cancer cell line  studies,  with Aphton's
G17DT in combination with  gemcitabine.  In the in vivo study, with tumor weight
as the principal  measure,  the combined benefit was a reduction of tumor weight
of 55%,  a  statistically  significant  (p=0.025),  45%  benefit  over that with
gemcitabine alone. The investigators  concluded:  "Anti-G17DT antibodies provide
an additional  anti-tumour effect over that which can be achieved by gemcitabine
alone in the treatment of pancreatic cancer."

It is  estimated  that there are  approximately  570,000  patients  with gastric
cancer in the US, Europe and Japan alone.  The  prognosis  for the  overwhelming
majority of these  patients is very poor.  Patients  diagnosed  with  metastatic
disease have five-year  survival rates of only about three percent.  Surgery and
chemotherapy are the primary  treatment options  currently,  but have shown only
very limited  benefit.  Aphton believes that its  anti-gastrin  approach has the
potential to extend life without adding toxicity to the therapeutic regimen.

Aphton is conducting one Phase III and three Phase II clinical trials.  Aphton's
anti-gastrin  targeted therapy induces  antibodies in patients that bind to both
gastrin 17 and gly-gastrin and remove them from circulation before they can bind
to the cancer  cell and  initiate  cell  growth.  (Aphton  believes  this is the
optimum  method  for  achieving  "growth  factor  inhibition.")  Gastrin  17 and
gly-gastrin  are  believed  to be  central  growth  factors,  or the  initiating
signals, for cell growth, cell proliferation and metastasis (spread) in gastric,
ie. stomach, pancreatic,  esophageal, colorectal and other gastrointestinal (GI)
system cancers. This signaling program is accomplished by gastrin binding to the
large numbers of gastrin  receptors which appear, de novo, in the great majority
of  cases,  on tumor  cell  surfaces  throughout  the  gastrointestinal  system.
Interrupting  this process by immunizing the patient with Aphton's  anti-gastrin
immunogen is a precisely "targeted" immunotherapy. This specificity of targeting
only cancer cells occurs  because  gastrin is not normally  secreted and gastrin
receptors  are not normally  found on "healthy"  cells in the GI system,  unless
they are malignant, or on the path to malignancy (except for cells involved with
normal acid secretion).  Recent findings have shown that inhibiting  gastrin not
only inhibits  cell growth,  proliferation  and  metastasis  directly,  but also
"unblocks" a central pathway leading to cell-suicide (apoptosis). This tilts the
balance,   from  cell  growth,  to  cell  suicide.   This  effect  is  amplified
synergistically  when Aphton's drug is given  together with a  chemotherapeutic.
Gastrin also stimulates the secretion and expression of other  important  growth
factors and receptors within and on the surfaces of the cancer cells involved in
tumor growth.  Hence,  inhibiting  gastrin inhibits all of the foregoing factors
contributing to tumor growth and spread, while simultaneously  opening a central
pathway to cell suicide.  Aphton's  anti-gastrin  targeted  immunotherapy adds a
biological dimension to the treatment of gastrointestinal cancers.

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Aphton Corporation is a biopharmaceutical  company developing products using its
innovative  targeted  immunotherapy  technology for  neutralizing  hormones that
participate  in  gastrointestinal  system  and  reproductive  system  cancer and
non-cancer  diseases;  and the  prevention  of  pregnancy.  Aphton has strategic
alliances with Aventis Pasteur (NYSE: AVE) for treating  gastrointestinal system
and other  cancers  with G17DT;  GlaxoSmithKline  (NYSE:  GSK) for  reproductive
system cancer and non-cancer diseases; and others.

Except for the historical  information  herein, the matters discussed herein are
forward-looking  statements that involve a number of risks and uncertainties and
are not a guarantee of future performance. Future results may vary significantly
based on a  number  of  factors  including,  but not  limited  to,  intellectual
property  risks,  risks in regulatory and market  acceptance of new products and
continuing  demand for same,  the impact of  competitive  products  and pricing,
changing  economic  conditions  and other risk  factors that are inherent in the
drug development process and the company's business including those set forth in
Aphton's  most recent 10-K and other  filings with the  Securities  and Exchange
Commission. It is not possible to predict or identify all such risk factors that
could cause actual  results to differ from expected or historical  results.  The
company's actual results could differ from these forward-looking  statements and
the company  undertakes  no obligation  to update  publicly any  forward-looking
statement.

Contact: Aphton Corporation; Investor Relations, J.L. Whitmore, 305-374-7338

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