Cancer & HIV Controlled With ONCONASE, A Novel RNase Therapeutic

Carmine M. Zingarino gn686 at cleveland.Freenet.Edu
Sat Apr 15 22:22:47 EST 1995


The article is appended to this message.

Cancer & HIV Controlled With ONCONASE, A Novel RNase Therapeutic
by Carmine M. Zingarino

1  INTRODUCTION - What is ONCONASE? (1-8,11-19)

   The word "ONCONASE" is a contraction of the words ONCOLOGY and 
RIBONUCLEASE (RNASE).  It is used to identify a protein substance that 
possesses anti-cancer properties and RNase specific enzymatic 
activities.
   In fact, Onconase is a ribonuclease protein (RNase) derived from the 
eggs (oocytes) and early embryos of the leopard frog "Rana pipiens." It 
is a novel p
rotein based on its comparison with over 10,000 other 
proteins registered with the National Biomedical Research Foundation 
Protein Identification Resource.  Though the scope of its anti-cancer 
activity embraces a wide variety of tumor cell types, it is especially 
active against carcinomas (i.e. solid tumor cancers), which may account 
for about 90% of all cancers.  Alfacell Corporation - a 
biopharmaceutical company located in Bloomfield, New Jersey - is 
credited with the discovery of this RNase prote
in.  
   In addition to the anti-tumor properties just noted Onconase also 
possesses anti-viral activity.  In particular, scientists at the 
National Institutes of Health (NIH) have shown that Onconase is active 
against the HIV-1 virus, the causative agent of AIDS.  NIH studies 
demonstrate that Onconase inhibits replication of the HIV-1 virus up to 
99.9% "in vitro" within 4 days.
   The scientific data clearly demonstrates that Onconase has 
considerable potential in the treatment of cancer and HIV inf
ections.  
These considerations convinced the Food and Drug Administration (FDA) in 
January 1995 to approve Onconase for a  Phase III clinical trial 
involving pancreatic cancer.  In fact, Onconase is the first RNase drug 
to reach this stage of clinical testing.  Consequently, it represents an 
entirely new approach to the treatment of cancer and viral infections.  
This article summarizes the scientific research and developmental 
history of ONCONASE (P-30 protein), a novel RNase therapeutic.

_________
______________________________________________________________

2  CONTENTS

1  Introduction - What is ONCONASE?
2  Contents
3  Basic Science Research
3.1  Basic Chemistry & Physical Characteristics
3.1.1  Primary Structure
3.1.2  Secondary & Tertiary Structure (X-ray Crystallographic Studies)
3.1.3  Enzymatic Properties of the RNase Subunit
3.2  Biological Activity Profile
3.2.1  Anti-cancer Activity
3.2.1.1  "In vitro" anti-tumor activity
3.2.1.1.1  Early "in vitro" studies 
           (Cytotoxic/Cytosta
tic Activity Observed)
3.2.1.1.2  Hypothesized Cytotoxic Mechanism of Action
3.2.1.2   Synergism with other chemotherapeutic agents
3.2.1.3   "In vivo" anti-tumor activity in mice
3.2.2  Anti-HIV Activity
4  Clinical Studies
4.1  Phase I Clinical Trial -  Toxicity Profile /
                               Objective Clinical Activity Noted
4.2  Phase II/III Clinical Trial
4.2.1  Clinical Response in Pancreatic Cancer Patients
4.3  A Clinical Trial for HIV?
5  Uniqueness of the Onconase Protein Molecule
6  Cu
rrent Research
6.1  National Institutes of Health (NIH)
6.2  National Cancer Institute (NCI)
6.3  Other Biologically Active Proteins
7  Summary
8  References
_______________________________________________________________________

3  BASIC SCIENCE RESEARCH

3.1  Basic Chemistry & Physical Characteristics

3.1.1  Primary Structure (4,17)

   The Onconase protein molecule is a single chain of 104 amino acid 
residues.  It has a calculated molecular mass of 11,834 Daltons, and is 
rich in the basic amino acid
 lysine.  A total of twelve lysine residues 
or approximately 11.54% of the molecule is composed of lysine.  It is a 
novel protein based on the comparison of its amino acid sequence with 
over 10,000 protein sequences registered with the National Biomedical 
Research Foundation Protein Identification Resource.
   The sequence homology demonstrates that it belongs to the pancreatic 
RNase superfamily.  In fact, it is the smallest member of this 
superfamily known to date.  Onconase demonstrates 30% identit
y with 
RNase A and 27% identity with bovine seminal RNase (BS-RNase).  Both 
Onconase and BS-RNase exert growth-inhibitory activity on neoplastic 
cell lines (9).  These considerations support the notion that proteins 
belonging to the RNase superfamily exhibit tumor growth-inhibitory 
activity.

3.1.2  Secondary & Tertiary Structure
       (X-ray Crystallographic Studies) - (7,19)

   The secondary structure reveals 40.4% antiparallel Beta strand, 20.2% 
helix, 39.4% turns and aperiodic segments (loops).
  The antiparallel 
Beta strands are manifested as two three-stranded Beta sheets.  This 
gives the molecule a bilobate appearance.  These strands are designated 
Beta-1, Beta-3, Beta-4 in the first Beta sheet and Beta-2, Beta-5, 
Beta-6 in the second Beta sheet. The residues assigned a helical 
conformation form three helices Alpha-1, Alpha-2 and Alpha-3.  The 
Alpha-1 helix is entirely alpha-helical in nature.  The other two alpha-
helices are distorted and contain mixtures of alpha-helix and 3(10) 
heli
x.  Nevertheless, the structural roles of the Alpha-2 and Alpha-3 
helices are similar.  Both pack against one of the three stranded 
antiparallel Beta sheets.  In each the helix axis is almost 
perpendicular to the strand direction.  The balance of the molecule 
includes four reverse turn segments and several aperiodic segments.
   Additionally, Onconase is a disulfide rich protein molecule.  It 
contains eight cysteine residues which form four disulfide bonds.  Three 
of these four bonds have counterpart
s in RNase A.  The fourth disulfide 
bond is unique to the amphibian members of the RNase superfamily.
   The active site is a long cleft formed at the junction of helix 
Alpha-1, strand Beta-1 and strand Beta-6.  It runs almost parallel to 
strand Beta-6.  Seven amino acid residues contribute to the active site.  
They include: an N-terminal pyroglutamyl residue (Pyr1), Lys9, His10, 
Lys31, Thr35, His97 and Phe98.

3.1.3  Enzymatic Properties of the RNase Subunit (4,19)

   Onconase's RNase subunit is esp
ecially active against highly 
polymerized ribosomal RNA.  This activity is essential to its 
antiproliferative effect.  Though Onconase and RNase A have a similar 
pyrimidine sensitive endoribonucleolytic activity, Onconase is 
specifically active against uridylyl-3',5'-guanosine (UpG) and 
cytidylyl-3',5'-guanosine (CpG).  RNase A by contrast hydrolyzes all 
diribonucleotide combinations that begin with a pyrimidine (UpX, CpX 
where X = A,C,G,U).  In either case ribonucleolytic activity proceeds in 
two 
steps (i.e. an intramolecular transesterfication followed by 
hydrolytic cleavage of the cyclic phosphate intermediate).  The result 
is a polyribonucleotide that ends with a 3'-phosphoester of cytidine or 
uridine.  This reaction is catalyzed in both Onconase and RNase A by 
three homologous amino acid residues (i.e. two histidine residues and 
one lysine residue).  With Onconase these are His10, Lys31 and His97. 

3.2  Biological Activity Profile

3.2.1  Anti-Cancer Activity

3.2.1.1  "In vitro" anti-tum
or activity

3.2.1.1.1  Early "in vitro" studies (Cytotoxic/Cytostatic
           Activity Observed) (1,2,3,17)

   Onconase exerts a powerful effect on the cell proliferative cycle in 
tumor cell cultures.  Flow cytometry measurements demonstrate that an 
accumulation of G1 phase cells, and  a decrease in both S phase (DNA 
synthesis) and G2+M (mitosis) fractions occurs in treated cell cultures.  
The increase in the proportion of G1 phase and decrease in S phase cells 
suggests that Onconase either arres
ts a portion of the cells in G1 or 
prolongs duration of G1 phase of all cells (cytostatic effect).  
Alternatively, Onconase may be selectively toxic to S phase cells 
(cytotoxic effect).  Cells with low RNA content also were observed in G1 
phase.  This is a feature typical of quiescent cells, and suggests that 
Onconase may trigger transition of cells from the cell cycle to 
quiescence.  Such an event in tumor cells is short lived and can result 
in loss of cell viability (1).
   "In vitro" studies on h
uman colorectal carcinoma (COLO 320DM) have 
been performed by Dr. Vincent Allfrey at Rockefeller University in New 
York.  Based on these studies Dr. Allfrey concludes that Onconase (P-30) 
contributes to the down regulation of the c-myc oncogene and, at higher 
doses, contributes to increased expression of the c-fos gene.  Dr. 
Allfrey claims this combination of events may be consistent with a 
differentiation inducing effect(s) (2,3).  As already noted Onconase 
inhibits cell cycle progression from G1 t
o S phase.  Since the degree of 
c-myc expression is inversely correlated with the duration of G1 phase, 
this observation concurs with the decreased c-myc expression observed by 
Dr. Allfrey (3).
   Nevertheless, tumor cells are ostensibly more susceptible to Onconase 
than are normal cells.  Some scientists contend that the malignant 
phenotype of tumor cells may mimic characteristics of early embryonal 
cells.  Since Onconase is derived from oocytes and early embryos of 
"Rana pipiens," it could exploit
 this feature and act preferentially 
against tumor cells.  Alternatively, it could be substituting for a 
specific anti-growth factor deficiency in tumor cells (3).
   These considerations suggest that Onconase may play a role in the 
determination of cell fate.  In particular, it may induce tumor cell 
apoptosis (i.e. programmed cell death) (15).
   Onconase is unique in its pattern of anti-tumor activity against a 
variety of cultured human tumor cell lines "in vitro."  Additional 
research studies demo
nstrate that it halts cell cycle progression in 
either the G1 or G2 phase of the cell cycle.  This was determined by MTT 
assay (Microculture tetrazolium assay), clonogenicity, and flow 
cytometry studies in four human tumor cell lines  (i.e. HL-60 human 
leukemia cells, COLO 320DM human colon adenocarcinoma, A-253 human 
submaxillary carcinoma, and A-549 human lung adenocarcinoma).  With 
HL-60, COLO 320DM and A253 cells Onconase inhibited cell cycle 
progression in the G1 phase.  A-549 cells, however, w
ere inhibited in 
the G2 phase (1,2,16).

______________________________________________

Note: Flow cytometry studies were performed by Zbigniew Darzynkiewicz, 
M.D., Ph.D. and his associates.  Dr. Darzynkiewicz is director of the 
Cancer Research Institute at the New York Medical College and professor 
of medicine at New York Medical College.  The flow cytometry studies 
were performed during his tenure with Sloan-Kettering Institute for 
Cancer Research in Rye, New York.

3.2.1.1.2  Hypothesized Cytotox
ic Mechanism of Action (13)

Based on studies performed by Dr. Richard Youle at the NIH Onconase's 
cytotoxic mechanism of action has been partially delineated.  Here is a 
summary of the events involved in this cytotoxic mechanism.

Onconase Cytotoxic Mechanism of Action

1) The Onconase molecule appears to have a distinct affinity for 
   receptors on tumor cells.  As a result, Onconase molecules bind 
   preferentially to these tumor cell surface receptors.  This also 
   demonstrates that the molecule 
possesses a receptor binding moiety in 
   addition to a RNase enzymatic subunit.

2) The binding event ostensibly induces a conformational change in the 
   cell membrane cytoskeleton that leads to endocytosis with the bound 
   Onconase molecule.  Consequently, cytosolic internalization of the 
   molecule may occur by endocytosis.  

3) Cytosolic routing of the internalized molecule is a subject of 
   current investigation.  However, once entry to the cytosol is 
   accomplished, ribonucleolytic degrad
ation of RNAs occurs.  In 
   particular, the enzymatic subunit hydrolyzes the 18S and 28S 
   subunits of the ribosomal RNA (rRNA).

   Recall that cells having low RNA content in G1 phase were revealed by 
   flow cytometry measurements.  This observation, therefore, is 
   consistent with the degradation of rRNA.

   Note that the ribosomes are the infrastructure upon which cell 
protein synthesis occurs.  Once the ribosomes have been degraded through 
Onconase hydrolysis of rRNA, protein synthesis is i
nhibited.  This may 
result in cell death.
   Also note, Onconase is an amphibian RNase.  Consequently, mammalian 
RNase inhibitors have no effect on its activity.  Its RNase activity, 
therefore, is unrestrained in mammalian tumor cells.  This makes 
Onconase an effective cytotoxin in extremely small concentrations 
(e.g. 1 x 10 -6 M).

3.2.1.2  Synergism with other chemotherapeutic agents (2,6,8,11,17)

   Onconase as a single agent is an exceptional anti-cancer compound. It 
can either inhibit tumor cel
l growth or kill tumor cells (i.e. is 
cytotoxic).  Nevertheless, its anti-cancer activity can be potentiated 
when used in combination with other chemotherapeutic drugs.  Onconase 
acts in a synergistic fashion with these other drugs.  Its cytotoxic 
effect was especially pronounced when used with anti-estrogen compounds 
(e.g. Tamoxifen).  Besides Tamoxifen, Onconase has been studied with 
Trifluoperazine (Stelazine), Lovastatin, and Cisplatin.  The performance 
of these therapeutic combinations were eva
luated on a variety of human 
cancer cell lines.  Researchers have concluded that Onconase and 
Tamoxifen work effectively on  ASPC-1 pancreatic adenocarcinoma and 
OVCAR-3 ovarian carcinoma.  Onconase and Trifluoperazine work 
effectively on A-549 lung adenocarcinoma.  Onconase and Lovastatin are 
effective against ASPC-1 pancreatic adenocarcinoma, OVCAR-3 ovarian 
carcinoma, A-549 lung adenocarcinoma and HT-520 lung carcinoma.  
Onconase and Cisplatin are effective against OVCAR-3 ovarian carcinoma.

3.2
.1.3  "In vivo" anti-tumor activity and 
          primary toxicology studies (3)

   The success of the "in vitro" studies motivated several researchers 
to examine Onconase's activity "in vivo."   Accordingly, "in vivo" 
studies of Onconase's toxicity and efficacy were performed on mice, rats 
and dogs.  The results of these studies were extremely encouraging.
   For example, BALB/c mice with M109 mouse Madison lung carcinoma had 
an ILS (Increased Life Span) of over 180% when treated with Onconase.  
Th
is is in contrast with control groups that were untreated.  Animals 
treated on a weekly bolus schedule showed less toxicity and greater 
antitumor response than those treated on a daily schedule.  In fact, the 
majority of the long term survivors were treated on the weekly schedule. 
All twelve survivors of this study were apparently cured of cancer.  
A dose dependent toxicity was noted that consisted of weight loss, 
diminished vigor, reduced food intake and ruffled coat.  However, the 
observed toxicit
ies disappeared when treatment was withdrawn.

3.2.2  Anti-HIV Activity (16,18)

   Studies performed by Dr. Richard Youle at the NIH demonstrate that 
Onconase inhibits HIV-1 viral replication in H9 Leukemia cells 
"in vitro" by 90 to 99.9% within 4 days.  Moreover, the Onconase 
concentrations used in the study were not toxic to uninfected H9 cells.
   The research data intimates that Onconase's entry to the white blood 
cell cytosol is viral assisted.  The research team believes that 
Onconase molecules
 become associated with either the viral particle or 
the area of the cell membrane through which the virus enters.  
Consequently, Onconase molecules may enter the cell with the HIV-1 
virions.
   Four members of the RNase superfamily were studied for anti-HIV 
activity by the research team. These four RNases are eosinophil derived 
neurotoxin (EDN), bovine pancreatic RNase A, Onconase and bovine seminal 
RNase (BS-RNase).  Only Onconase and BS-RNase demonstrated anti-viral 
activity.  However, the anti-v
iral activity displayed by Onconase was 
significantly greater than the activity observed with BS-RNase.
   When white blood cells become infected with the HIV-1 virus, an 
exponential increase in the production of certain viral proteins occurs 
(e.g. p24 antigen and reverse transcriptase).  Therefore, we can measure 
the degree of viral replication by examining the levels of these 
proteins.  As a result, the research team observed one such protein 
throughout the study after treatment with each of the fo
ur RNases.  The 
viral p24 antigen was selected for this purpose.
   Onconase inhibited p24 expression by 99 to 99.9% at a concentration 
one order of magnitude less than the concentration required for 
cytotoxicity in cancer cells.  Moreover, p24 expression was reduced 
significantly the first day after viral infection.  Even with 
concentrations that were two orders of magnitude less than the cytotoxic 
amount Onconase inhibited viral replication.  About 90% inhibition was 
achieved within four days at t
hese concentrations.  So, the study 
concludes that subtoxic concentrations of Onconase are very effective at 
inhibiting viral replication.
   The research study also demonstrates that Onconase does not operate 
on the virus outside the cell.  It must enter the cell with the virus to 
inhibit viral replication.
   Besides the increase in viral proteins, the formation of syncytial 
cell aggregates is observed in HIV-1 infected cells.  However, when 
these infected cells are treated with Onconase, the forma
tion of 
syncytial cell aggregates is abrogated.  In fact, the cells are 
indistinguishable from uninfected cells.  This histological view 
correlates perfectly with the biochemical data on reduced viral p24 
antigen levels.

Anti-Viral Mechanism of Action

   The research team hypothesizes that the mechanism of Onconase's anti-
viral activity may be similar to its anti-cancer activity.  Once inside 
the white blood cell, Onconase may hydrolyze the cell's ribosomal RNA.  
Since viral protein production dep
ends on the integrity of the host 
cell's ribosomes, any degradation of the ribosomes will have an impact 
on viral replication.
   Note, HIV-1 is a RNA virus.  Its genetic material is composed of RNA 
not DNA as in most other life forms.  Accordingly, the HIV-1 viral RNA 
could be vulnerable to hydrolytic attack by Onconase.  This also would 
inhibit viral replication.  However, further study is needed to confirm 
this.
   A primary concern of medical professionals is controlling the virus's 
ability to r
einfect neighboring white blood cells (i.e. lateral 
transmission).  Consequently, any activity that degrades either the 
ribosomes or the viral RNA could help slow the rate of this infection.

Augmentation of Anti-HIV Activity

   The research team also suggests that Onconase conjugates could be 
engineered to target HIV infected cells.  These conjugates may increase 
Onconase's endogenous anti-viral activity.  The research team considers 
CD4 and monoclonal antibodies that bind HIV infected cells as pote
ntial 
candidates for conjugation with Onconase.  With this technique the 
Onconase conjugate would compete with the virus for available CD4 
receptor binding sites.  Moreover, the rate of Onconase's entry to the 
cell cytosol would increase.  This also would help slow the rate of 
reinfection in neighboring white blood cells.

4  CLINICAL STUDIES

   The FDA officially recognized Onconase as a drug substance possessing 
anti-tumor activity in October 1987.  Having cleared this major 
regulatory hurdle, On
conase began Phase I clinical trials in April 1989.  
This section reviews some clinical trial results.

4.1  Phase I Clinical Trial - Toxicity Profile /
                              Objective Clinical Activity Noted (5,12)

   Twenty - eight patients were administered a weekly intravenous (IV) 
bolus of Onconase (ONC) in the Phase I study.   The goal of the Phase I 
study was to assess the maximum tolerated dose (MTD), and the safety and 
toxicity of Onconase in these patients.  This study demonstrated t
hat 
Onconase was well tolerated by the majority of Phase I patients.  It 
exhibited a consistent and reversible clinical toxicity pattern, and did 
not induce most of the toxicities usually associated with other 
chemotherapeutic agents such as alopecia (hair loss) and myelosuppression 
(bone marrow suppression).  A study of the clinical symptoms demonstrated 
that peripheral edema (i.e. swelling of the appendages due to water 
retention) and asthenia (i.e. weakness and fatigue) were the two main 
side ef
fects of Onconase treatment.
   The high degree of homology to known low-immunogenicity proteins 
suggests that Onconase may be weakly immunogenic if at all to humans.  
Nevertheless, there was no clinical evidence of a true immunological 
sensitization to the drug.  In fact, Onconase served to boost the human
body's natural defense mechanisms by contributing to an increase in the 
total white blood cell count.  Consequently, the research team 
concluded that the drug is safe to humans.  The maximum tolera
ted weekly 
IV bolus dose (MTD) of Onconase was 960 ug/m2 (16X), with the dose 
limiting toxicities being renal, (i.e. dependent on kidney function).  
The anticipated human dose is 60 ug/m2 (1X).  Dose levels are stated as
micrograms per square millimeter of human body surface area (ug/m2).
   Objective clinical responses were observed in Phase I patients with 
advanced and resistant to therapy tumors.  Six of the twenty-eight 
patients treated with Onconase responded to treatment.  This represents 
a res
ponse rate of 21.43% in the Phase I trial.  The responses ranged 
from stabilization of disease to partial remission.  Stabilization of 
disease (SD) was observed in three patients.  One of these patients had 
a malignant thymoma, another had a colorectal carcinoma, and the third 
had a non-small cell carcinoma (NSC) of the lung. A minor response (MR) 
was observed in a patient with colorectal carcinoma.  In fact, this tumor 
had metastasized to the lungs.  Two partial remissions (PR) of the 
disease were 
also observed.  One was seen in a patient with an 
adenocarcinoma of the lung and one in a patient with esophageal carcinoma. 
The tumor in the patient with esophageal carcinoma also had metastasized 
to the lungs.  Recall that the goal of the Phase I study was to assess 
the maximum tolerated dosage, safety, and toxicity of Onconase.  
Nevertheless, the clinical responses just noted demonstrate that some 
efficacy was observed.

Criteria For Clinical Response (12)

This section lists the criteria used by 
the clinical research team to
evaluate clinical response.

CR: Complete Remission   Disappearance of all clinical evidence of active
                         tumor, and patient free of any symptoms related 
                         to cancer for at least one month.

PR: Partial Remission    50% or greater decrease in the sum of the 
                         products of the bidimensionally measured diameters 
                         of all measurable tumor lesions; no simultaneous 
                        
 increase in the size of any lesion or appearance  
                         of any new lesions.

MR: Minor Response       Response less than PR but more than SD, 
                         i.e. between 25 to 50%.

SD: Stable Disease       Steady state or response less than 25%.

PD: Progressive Disease  Unequivocal increase of at least 25% in the size
                         of any measurable lesion, or the development of
                         new metastatic lesions.

Relapse:                 The appea
rance of new lesions; the re-appearance
                         of old lesions in patients who were in CR.
                         For patients in PR, an increase of 25% or more
                         in the sum of the products of the diameters of
                         all measured tumors over that which was obtained
                         at the time of maximum regression.

4.2  Phase II/III Clinical Trial

   Phase II clinical trials establish safety and efficacy.  Onconase began 
Phase II clini
cal trials in January 1991.  A total of 245 patients with a 
variety of tumor types have been studied in this trial.  Among these are: 
51 pancreatic carcinoma patients, 43 non-small cell (NSC) lung cancer 
patients, 11 mesothelioma patients, 17 breast cancer patients, 18 melanoma 
patients, 50 colorectal cancer patients and 55 patients with other cancers.  
In pancreatic cancer patients Onconase is being studied in combination 
with Tamoxifen.
   Analysis of the drug's safety on all 245 patients has been 
completed, 
and the safety profile is excellent.  Analysis of efficacy has been 
completed for the pancreatic carcinoma patients and the NSC lung patients.  
These results have been submitted for publication.  Efficacy evaluation of 
the remaining patients and cancer types is in progress.

4.2.1  Clinical Response In Pancreatic Cancer Patients

   Pancreatic cancer claims the lives of more than 25,000 Americans a 
year.  It has a median survival rate of 90 days, and no standard 
effective treatment current
ly exists for this disease.  Moreover, new 
chemotherapeutic compounds have been tested in these patients 
unsuccessfully.  For example, Tamoxifen as a single agent has been 
completely ineffective in the treatment of this disease (10).
   On the other hand, Onconase as a single agent is moderately effective 
in the treatment of pancreatic adenocarcinoma.  Moreover, as the 
"in vitro" studies have established, the synergism between Onconase and 
anti-estrogen compounds (e.g. Tamoxifen) can produce a potent
iated anti-
tumor response.  Accordingly, a combination therapy of Onconase and 
Tamoxifen was administered to fifty-one advanced and resistant to therapy 
pancreatic carcinoma patients.  The recently completed Phase I/II study 
demonstrates that this combination therapy is active against advanced 
pancreatic adenocarcinoma.
   Forty-six of the patients, or 90% were diagnosed as having Stage 4 
disease.  This means that the cancer had spread beyond the pancreas to 
distant sites in these patients.  Thirty-
two patients were evaluable 
(i.e. they were administered at least 3 doses of Onconase).  As of 
October 31, 1994 the median survival of these thirty-two patients was 
3.7 months.  In eight of these patients (i.e. 25%) objective clinical 
activity was observed.  With one individual achieving complete remission 
(CR).  As of October 31, 1994 this individual was alive and cancer-free 
more than 3.6 years after entering the study.  Seven other patients 
achieved stabilization of disease (SD) with a median sur
vival of 1.6 
years.  Median survival for these eight patients was 2.2 years.  This 
survival is considerably longer than the median survival range of 7.5 
months to 12 months for the best responders (CR and PR only) in the 
leading pancreatic cancer trials conducted over the past two decades 
(i.e. approximately 2 to 3.5 times longer).  As of October 31, 1994 five 
patients were alive, with survivals ranging from 1.6 years to 3.6 years 
after study entry.  All survivors had Stage 4 disease upon study entr
y.  
Understandably, the FDA approved Onconase for a Phase III clinical trial 
involving pancreatic cancer in January 1995.
___________________________________________________

Directors of the Clinical Trials Program

Clinical studies are under the direction of John J. Costanzi, M.D.; 
David N. Mesches, M.D. and Abraham Mittelman, M.D.

John J. Costanzi, M.D. has served as a principal investigator in the 
Onconase clinical trials program since its inception.  He is currently 
in the practice of oncology a
nd hematology in Austin, Texas.  Dr. 
Costanzi formerly served as medical director of the Thompson Cancer 
Survival Center in Knoxville, Tennessee.  He also was director of the 
cancer center for the University of Texas Medical Branch in Galveston.

David N. Mesches, M.D., is professor and chairman of the department of 
family medicine at New York Medical College.  The original Onconase 
Phase I clinical trials were initiated and completed under his direction.

Abraham Mittelman, M.D., is assistant profess
or of medicine and director 
of experimental oncology at New York Medical College in Valhalla, New 
York.  Dr. Mittelman is an oncologist and hematologist who has been the 
principal investigator of numerous cancer trials.

4.3  A Clinical Trial for HIV?

   In consideration of the "in vitro" studies performed by the NIH on 
HIV-1 infected H9 Leukemia cells an Onconase clinical trial for HIV is 
likely.  In fact, it is an issue that is being actively discussed.

The Case For Early Human HIV Clinical Trials


Given the current data a compelling argument can be made for initiating 
a Phase I/II human HIV clinical trial with Onconase.

Consider the following:

   Since the "in vitro" study demonstrates that Onconase has significant 
anti-viral activity against HIV-1, we would expect "in vivo" animal 
testing to follow this study.  However,  a favorable human safety profile 
for Onconase has been established by the Phase I cancer clinical trial.  
This would obviate the need for further "in vivo" animal testing 
and 
another Phase I human clinical trial.  Moreover, subtoxic concentrations 
are required for anti-viral activity compared with the concentrations 
required for anti-cancer activity.
   Besides, a favorable regulatory environment exists.  The approval 
process has been shortened for drugs that demonstrate potential in 
treating life threatening illnesses.  AIDS is among the group of 
illnesses that have been classified by the FDA as life threatening (20).
   These arguments make Onconase a superb candida
te for a human HIV 
clinical trial.


5  UNIQUENESS OF THE ONCONASE PROTEIN MOLECULE

   Onconase is a novel protein molecule with a unique bioactivity profile.  
Some attributes of the molecule that make it structurally novel and 
functionally unique are listed here.

1) It is a structurally novel protein based on its comparison with over 
   10,000 other proteins registered with the National Biomedical Research 
   Foundation Protein Identification Resource.
2) The protein preferentially binds to membran
e receptors on tumor 
   cells.  This is followed by cytosolic internalization presumably by the 
   process of endocytosis.
3) The ribonucleolytic activity of the molecule is not inhibited by 
   mammalian RNase inhibitors.  As a result, the mammalian ribosomal RNA 
   is degraded.  This leads to the inhibition of protein synthesis and 
   cell growth.
4) Attributes 2 and 3 make Onconase selectively cytotoxic to tumor cells.
5) Entry to the cytosol of viral infected cells may be facilitated due to
   the 
molecule's small size.  This characteristic may allow it to become
   trapped within a viral endosome, and internalized with a viral particle.
   Consequently, its ribonucleolytic activity can inhibit viral replication
   (e.g. HIV-1).
6) Onconase serves to boost the human body's natural defense mechanisms.
   For example, it contributes to an increase in white blood cell counts.
7) Protein molecules that are foreign to the human body are usually 
   immunogenic in humans.  Although the onconase protein is
 foreign to 
   the human body, it has a high degree of homology (i.e. similar 
   molecular structure) to known low-immunogenicity proteins (e.g. 
   RNase A, a human pancreatic RNase and angiogenin).  Its molecular 
   structure has been well conserved over evolution.  Therefore, it may 
   be only weakly immunogenic if at all in humans.
8) The major dose dependent toxicities are peripheral edema and asthenia.
   Nevertheless, the observed toxicities are reversible upon withdrawal of 
   treatment.

6  C
URRENT RESEARCH

6.1  National Institutes of Health (NIH)

   The NIH is engaged in the development of Onconase conjugates and 
recombinant Onconase.  Areas of research at the NIH include studies of 
anti-HIV activity, the study of the molecular mechanism(s) of action of 
Onconase at the cellular and subcellular levels, tests of the anti-tumor 
activities of Onconase conjugates (14), Onconase gene therapy, and 
investigation of anti-tumor activity of Onconase against primary brain 
tumors.

6.2  National C
ancer Institute (NCI)

   Onconase also is being tested at the National Cancer Institute's 
Biological Response Modifier and Developmental Therapeutics Programs.  
Areas of research include studies of Onconase as a single agent against 
various tumor cell lines (including the NCI Cancer Screen), and Onconase 
incorporated into liposomes both as a single agent and in combination with 
other drugs.  In particular, the NCI is examining Onconase's ability to 
overcome multiple drug resistance (MDR) in cancer t
herapy (e.g. colorectal 
cancer).  The NCI also is studying Onconase's anti-HIV activity.

6.3  Other Biologically Active Proteins

   In addition to Onconase, a series of biologically active proteins from 
the same amphibian natural source material have been discovered.  These 
proteins appear to be involved in the regulation of early embryonic and 
malignant cell growth.  So far two additional proteins have been purified 
and characterized.  These proteins have been tentatively named P-31 and 
P-32.

7  
SUMMARY

   Onconase is a novel protein molecule in both biological structure and 
function.  For example, it exhibits antiproliferative activity against a 
wide variety of tumor cell types.  Moreover, it has demonstrated activity 
against the HIV-1 virus, the causative agent of AIDS.
   The molecule's potential as both an anti-cancer and anti-viral 
therapeutic has been well documented in the scientific literature.  
Furthermore, safety and efficacy as an anti-cancer agent in humans have 
been established
.  As the first RNase therapeutic to reach Phase III 
clinical trials, Onconase represents a completely new approach to the 
treatment of cancer and viral infections.

8  REFERENCES

(1)  "Cytostatic and Cytotoxic Effects of Pannon (P-30), a Novel 
     Anticancer Agent." Z. Darzynkiewicz, S. Carter, S. Mikulski, 
     W. Ardelt, K. Shogen. Cell Tissue Kinet. 21:169-182, 1988.

(2)  "Tamoxifen and Trifluoroperazine (Stelazine) Potentiate Cytostatic/
     Cytotoxic Effects of P-30 Protein, a Novel Protein P
ossessing Anti-
     Tumor Activity." S. Mikulski, A. Viera, W. Ardelt, H. Menduke, K. 
     Shogen.  Cell Tissue Kinet. 23: 237-246, 1990.

(3)  "Striking Increase of Survival of Mice Bearing M109 Madison 
     Carcinoma Treated With a Novel Protein From Amphibian Embryos." 
     S. Mikulski, W. Ardelt, K. Shogen, E. Bernstein, H. Menduke. 
     J Natl Cancer Inst. 82(2): 151, Jan. 17, 1990.

(4)  "Amino Acid Sequence of an Anti-tumor Protein from Rana pipiens 
     Oocytes and Early Embryos." W. Ardelt, 
S. Mikulski, K. Shogen.  
     J Biol Chem. 266(1): 245-251, Jan 5, 1991.

(5)  "A Phase I Study of P-30 Protein (PP) Administered Intravenously on 
     a Weekly Schedule." J. J. Costanzi, A. Grossman, P. Carter, 
     A. Ebenezer, W. Hanna, K. Shogen, S. M. Mikulski. The Thompson 
     Cancer Survival Center, Knoxville, IN and Alfacell Corporation. 
     Proc. Amer. Soc. Clin. Oncol., Houston, TX. Abstract #286, 1991.

(6)  "Synergism Between a Novel Amphibian Oocyte Ribonuclease and 
     Lovastatin in 
Inducing Cytostatic and Cytotoxic Effects in Human 
     Lung and Pancreatic Carcinoma Cell Lines." S. Mikulski, A. Viera, 
     Z. Darzynkiewicz, K. Shogen.  Br J Cancer. 66: 304-310, 1992.

(7)  "Comparative Molecular Modeling and Crystallization of P-30 Protein: 
     A Novel Antitumor Protein of Rana pipiens Oocytes and Early Embryos." 
     S. Mosimann, K. Johns, W. Ardelt, S. Mikulski, K. Shogen, M. James.  
     Proteins Struct Funct Genet. 14: 392-400, 1992.

(8)  "In Vitro Synergism Between a Nove
l Amphibian Oocytic Ribonuclease 
     (ONCONASE) and Tamoxifen, Lovastatin and Cisplatin, in Human OVCAR-3 
     Ovarian Carcinoma Cell Line." S. Mikulski, A. Viera, K. Shogen.  
     Int J Oncol. 1: 779-785, 1992.

(9)  "In Vivo and in Vitro Growth-inhibitory Effect of Bovine Seminal 
     Ribonuclease on a System of Rat Thyroid Epithelial Transformed Cells 
     and Tumors." P. Laccetti, G. Portella, M.R. Mastronicola, A. Russo, 
     R. Piccoli, G. D'Alessio and G. Vecchio.  
     Cancer Res. 52: 4582-
4586, 1992.

(10) "Clinical trial of tamoxifen in patients with irresectable 
     pancreatic adenocarcinoma." O. M. Taylor,  E. A. Benson, 
     M. J. McMahon. Br J Surg. 80(3): 384-6, Mar 1993.

(11) "Human tumor cell growth modulatory effects of the AEBS/H IC-binding 
     drugs used as single agents and in combination with a novel 
     amphibian oocyte RNase." S. Mikulski, A. Viera and K. Shogen. 
     Int J Oncol. 2: 807-812, 1993.

(12) "Phase I human clinical trial of ONCONASE (P-30 protein) 
     
administered intravenously on a weekly schedule in cancer patients 
     with solid tumors." S. M. Mikulski, A. M. Grossman, P. W. Carter, 
     K. Shogen and J. J. Costanzi.  Int J Oncol. 3: 57-64, 1993.

(13) "A Cytotoxic Ribonuclease - Study of the Mechanism of ONCONASE 
     Cytotoxicity." Y-N. Wu, S. Mikulski, W. Ardelt, S. Rybak and 
     R. Youle. J Biol Chem. 268(14): 10686-10693, May 15 1993.

(14) "Cytotoxic Onconase and Ribonuclease A Chimeras: Comparison and in 
     Vitro Characterization." S.
 Rybak, D. Newton, S. Mikulski, A. Viera, 
     R. Youle. Drug Targeting Delivery. 1: 3-10, 1993.

(15) "Pathogenesis of cancer in view of mutually opposing apoptotic and 
     anti-apoptotic growth signals (Review)." S. Mikulski. 
     Int J Oncol. 4: 1257-1263, 1994.

(16) "RNase Inhibition of HIV Infection of H9 Cells." R. Youle, Y-N Wu, 
     S. Mikulski, K. Shogen, R. Hamilton, D. Newton, G. D'Alessio and 
     M. Gravell. Abstract: A-2. International Cytometry Symposium, 
     San Francisco, CA. Janu
ary 18-21, 1994.

(17) "Anti-tumor Properties of ONCONASE, A Novel Ribonuclease From The 
     Eggs And Early Embryos Of Leopard Frog (Rana pipiens)." S. Mikulski, 
     Z. Darzynkiewicz, W. Ardelt and K. Shogen. Abstract: J-2. 
     International Cytometry Symposium, San Francisco, CA. 
     January 18-21, 1994.

(18) "RNase inhibition of human immunodeficiency virus infection of H9 
     cells." R. Youle, Y-N. Wu, S. Mikulski, K. Shogen, R. Hamilton, 
     D. Newton, G. D'Alessio and M. Gravell.  
     P
roc Natl Acad Sci. 91: 6012-6016, June 1994.

(19) "Refined 1.7 A X-ray Crystallographic Structure of P-30 Protein, an 
     Amphibian Ribonuclease with Anti-tumor Activity." S.C. Mosimann, 
     W. Ardelt and M.N.G. James. J. Mol. Biol.  236: 1141-1153, 1994.

(20) "Faster Evaluation of Vital Drugs." D.A. Kessler and K.L. Feiden. 
     Scientific American 272(3): 48-54, March 1995.



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