DISTINGUISHED
SERVICE AWARD ADDRESS
Levamisole as an Adjuvant in Cancer Treatment Paul
A.
J.
MD,
Janssen,
I
n the early 1960s, there was a search for a superior anthelmintic drug. It had to be patentable, potent, safe, and active against a wide variety of worms, including their larval stages, both orally and by injection.
Our strategy was to synthesize as many relatively simple heterocyclic compounds as possible and to evaluate their anthelmintic activity in a critical test that used naturally infected chickens. For some time, it looked as if we were climbing trees to seek fish; the first 2721 compounds that were tested were ineffective. The next compound however, R 6438, (Figure) turned the tide in our favor; a single oral dose of 160 mg/kg removed all ascarids, heterakids, and capillana worms from the gastrointestinal tract of three chickens. We had a chemical lead and a morale boost precisely when they were needed. It soon became apparent, however, that R 6438 was not the end, but the beginning of a long story. It is exciting, in a sort of nostalgic way, to remember the subsequent period of intense interdisciplinary activity that produced the evidence that R 6438 was a pro-drug, metabolically converted into an active anthelmintic in chickens, but not in any other species. The active metabolite, R 8141, a novel imidazothiazol derivative, appeared to be a perfect candidate for development; it was high in potency, acceptably safe, soluble in water, and had a broad anthelmintic spectrum in all species. But, a closer look showed two serious drawbacks: limited stability in water and high production costs. Removal of the double bond of the thiazol ring and replacement of the thiophene ring by benzene administration resolved these two shortcomings. R 8299 was thus selected for further development and given the generic name tetramisole HC1. Most of the anthelmintic activity resides in the levorotatory isomer levamisole, whose absolute configuration is S. Tetramisole was first marketed as a veterinary anthelmintic in Belgium in 1965 and a year later
as a human tetramisole used worm infections poultry.
396
#{149} J ClIn Pharmacol
1991;31:396-400
Beerse, Belgium. MD, PhD, .Janssen
Research
anthelmintic in Brazil. As time passed, and levamisole became the most widely remedies for a broad range of nematodal in humans, cattle, pigs, sheep, and
SURPRISES The first indications that tetramisole and levamisole, when used in field conditions, did more than merely kill nematodes came from a variety of independent, and at first sight, unrelated observations. (1)Beagles
at Janssen
Pre-weaning mortality of the beagles in our colony traditionally averaged about 1/4, despite vaccination, vigorous hygiene, and deworming with piperazine. Pups generally died with symptoms of distemper, atrophy of the thymus, and toxacara larvae in various tissues. After tetramisole was found to have larvicidal activity, it was used instead of piperazine for deworming the bitch before whelping. One year later, only 1/10 of the pups died before weaning, and the year thereafter only 1/20 of the pups died. Transplacental toxocara infection disappeared. Atrophy of the thymus and distemper were no longer observed. Whether the larvicidal drug was active as an adjuvant, boosting the efficacy of the distemper vaccine, was questioned. (2)
African
School
Children
Mass treatment (one 50-mg tetramisole tablet every 3 months during a 2-year period) of African school children who lived in a highly contaminated environment led to a progressive decline in the incidence of roundworm, hookworm, and threadworm in the population that was treated. This decline suggests a beneficial effect of tetramisole on host-defense mechanisms.1 (3)
From the Janssen Research Foundation, Address for reprints: Paul A. J. Janssen, Foundation, B-2340 Beerse, Belgium.
PhD
Cattle
in
Chad
In Chad,
Provost
to increase
the
observed resistence
that in cattle
tetramisole against
seemed contagious
LEVAMISOLE
AND
abortus
OH CH,
R 6438
R 8141
0
\/ (‘)-(S) H’
NTS
Levamisole
Dexamisole
)
Tetramisole
Figure.
From
bovine
zero
to an active
in South
Sheep
In South chlamydial worming tion).
reduced
(personal
and
Pigs
In Australia,
Goodman
tion
weight
of
body
of de-
in Australia noted in
a sudden
tetramisole-treated
normaliza“poor-
doing” calves and pigs. This fect was apparently unrelated (personal communication).
puzzling beneficial efto worm problems
(6)
in Hawaii
In the
Antwerp
Zoo
genic (5)
and
reported
EXPLAINING
by
Fisher
THE
DISTINGUISHED
SERVICE
11
cytoreductive
days
later.
therapy,
B.
as
little or no effect subjects.124 Skin is boosted by
than
SURPRISES
AWARD
ADDRESS
normal
was
on antibody delayed hythe drug in
a variety by anergy
levels
all
CLINICAL
of those
action of tetrain worm-free
conditions,
depressed but
does
of diseases that or immunologic
TWO
possibly
similarly.17’18 of experimental
not
function stimulation
of to
occur.19-23
and many other similar observations, and hypotheses strongly suggested should be active in the treatment
In 1971, a large-scale started to empirically
in Hawaii.
to show the mechanism
react variety
normalized the and T-lymphocytes,
All of these considerations, that levamisole
caused deficiency.
FACES clinical test the
human
caused
are
or
diseases
systemic bacteria;
membranes,
OF LEVAMISOLE research effect
that
accompanied
infections
eyes,
that
program of levamisole
are by
respiratory
are
of
or accompanied
was in
definitely anergy
or or
paired cellular immune mechanisms.24 In summary, levamisole was effective not against various nematodal infections in humans animals, but also in the following four areas: 1. recurrent and chronic infections of the mucus
(1) The first experiment misole on a host-defense
stimulation In a wide
levamisole phagocytes
THE
In the Antwerp Zoo, Thienpont observed apparent cures after treatment with levamisole in ruminants and monkeys that were affected with herpes-like viral infections. Similar observations in monkeys were
killed
anergic patients with various malignant or other diseases such as leprosy.1416 Apparently, healthy elderly patients with reduced skin reactivity to anti-
Africa
Africa, Leroux noted a striking decrease infections in sheep after routine with tetramisole (personal communica-
Calves
by
(4) Levamisole has production in healthy persensitivity, however,
communica-
more
(5)
and
shown by Mike Chirigos in Bethesda.67 This effect of levamisole on stabilization of tumor remission has been observed in several models, including various leukemias, carcinomas, and sarcomas.8”
compound.
pleuropneumonia
organisms,
abortus organisms were grown from the spleens of these vaccinated mice, which indicated that they were incompletely protected against the challenge. However, when tetramisole was given 2 days after the B19 vaccine, the animals were fully protected.23 (2) Fischer showed that levamisole dramatically enhances immunologic protection against various bacterial and viral pathogens in suckling rats and suggested that the drug may be useful in the management of various infections in patients with impaired or immature immunity.45 (3) Levamisole has little or no effect on primary growth and dissemination of experimental tumors, but it can prevent relapse when the tumor mass is first
tion). (4)
TREATMENT
animals was published in 1971 by Renoux.2 Mice were vaccinated with antibrucella vaccine Big, challenged 42 days later with virulent Brucella
0 II N-C-CH, -CH
CANCER
caused
tract,
by
im-
only and skin,
as well
viruses
as
or
397
JANSSEN
TABLE I Controlled
Clinical Studies with Levamisole
First Author (Reference)
As An Adjuvant
Number Cancer
Basic Therapy
(25) KlefstrOm (26) Hortobagyi (27)
Breast Breast
Radiotherapy Cytostatics
Breast
Cytostatics
Stephens
Breast
Cytostatics
Lung
Surgery
Lung Lung Lung Head and neck Larynx Gastrointestinal Cob-rectal
Surgery + BCG Radiotherapy Cytostatics Surgery Surgery + radiotherapy Surgery Surgery
Rojas
(28)
Amery (29) Wright (30) Pines (31) Chahinian (32) Wanebo (33) Mussche (34) Miwa (35) Verhaegen (36) *
Patients
receiving
In Cancer Treatment
t+
levamisole;
= statistically
significant
difference in favor of levamisole;
2. postviral anergy, i.e., the slow recovery period after influenza, measles, characterized by prolonged physical and psychic asthenia; 3. rheumatic diseases, such as rheumatoid arthritis; and 4. in cancer patients, after apparently successful surgery, radiation therapy, or chemotherapy, but in whom relapse rate is high. As shown in Tables I and II, the results of 23 different controlled clinical studies with levamisole as
= not
of Patlents* (Start)
Effectf
20 49 114
+
29
+
96 46 33 24 26 12 143 30
+ ?
+ +
+
+ + +
evaluable.
an adjuvant in the treatment of 13 different types of cancer have been published. In 12 studies, levamisole was significantly superior to placebo (P < .05). In four studies, a statistically insignificant trend in favor of levamisole was reported. In two small trials, no difference with placebo was seen, and the results of the remaining five studies are not evaluable for various technical reasons. General scepticism prevailed, however, for more than a decade until, in 1989, a report that suggested a
TABLE II Controlled
Clinical Studies with Levamisole
Author (Reference)
As An Adjuvant
Number
First
Valdivieso
Cancer
(37)
Gonzalez (38) Hall (39) Takakura (40) Smith (41)
Debois (42) Vuopio
(43)
Brincker
Patients
receiving
Basic Therapy
levamisole;
S
J Clln Pharmacol
Effectf
Cytostatics Surgery
19 103
Melanoma
Cytostatics
60
Brain Bladder Various AML + ALL
Surgery + radiotherapy Surgery + radiotherapy Radiotherapy
31
?
33
(+)
186
(+)
Cytostatics Cytostatics Cytostatics
31 12 111
+
30
(+)
t+
statistically
Cytostatics
Cytostatics significant
difference
in
1991;31:396-.400
-
+
(+)
-
+
35 favor between
398
of Patlents* (Start)
Colo.rectab Melanoma
AML ALL ANLL NH lymphoma
(44)
Pavlovsky (45) Chang (46) Cabanillas (47) *
in Cancer Treatment
of levamisole; levamisole
(+)
= trend
and control;
?
in favor
= not
? of levamisole;
evaluable.
-
= no
difference
LEVAMISOLE
AND
possible benefit from the use of levamisole, alone or in combination with 5-fluorouracil (5-FU), as adjuvant therapy for colorectal cancer in Dukes’ stage B2 (invasion of serosa or pericolonic fat) or stage C (metastasis to regional lymph nodes) appeared from the North Central Cancer Treatment Group.48 These results were promising enough to justify a larger and more definitive study, which involved 1296 patients with resected colon cancer that either was locally invasive (stage B2) or had regional nodal involvement (stage C), by the Eastern Cooperative Oncology Group, the North Central Cancer Treatment Group, the Southwestern Oncology Group, and the Mayo Clinic.49 After a median follow-up time of 3 years for the patients with stage C disease, treatment with levamisole (3 X 50 mg daily for 3 consecutive days every second week) plus 5-FU reduced the risk of cancer recurrence by 41% (P
SERVICE AWARD ADDRESS
Levamisole as an Adjuvant in Cancer Treatment Paul
A.
J.
MD,
Janssen,
I
n the early 1960s, there was a search for a superior anthelmintic drug. It had to be patentable, potent, safe, and active against a wide variety of worms, including their larval stages, both orally and by injection.
Our strategy was to synthesize as many relatively simple heterocyclic compounds as possible and to evaluate their anthelmintic activity in a critical test that used naturally infected chickens. For some time, it looked as if we were climbing trees to seek fish; the first 2721 compounds that were tested were ineffective. The next compound however, R 6438, (Figure) turned the tide in our favor; a single oral dose of 160 mg/kg removed all ascarids, heterakids, and capillana worms from the gastrointestinal tract of three chickens. We had a chemical lead and a morale boost precisely when they were needed. It soon became apparent, however, that R 6438 was not the end, but the beginning of a long story. It is exciting, in a sort of nostalgic way, to remember the subsequent period of intense interdisciplinary activity that produced the evidence that R 6438 was a pro-drug, metabolically converted into an active anthelmintic in chickens, but not in any other species. The active metabolite, R 8141, a novel imidazothiazol derivative, appeared to be a perfect candidate for development; it was high in potency, acceptably safe, soluble in water, and had a broad anthelmintic spectrum in all species. But, a closer look showed two serious drawbacks: limited stability in water and high production costs. Removal of the double bond of the thiazol ring and replacement of the thiophene ring by benzene administration resolved these two shortcomings. R 8299 was thus selected for further development and given the generic name tetramisole HC1. Most of the anthelmintic activity resides in the levorotatory isomer levamisole, whose absolute configuration is S. Tetramisole was first marketed as a veterinary anthelmintic in Belgium in 1965 and a year later
as a human tetramisole used worm infections poultry.
396
#{149} J ClIn Pharmacol
1991;31:396-400
Beerse, Belgium. MD, PhD, .Janssen
Research
anthelmintic in Brazil. As time passed, and levamisole became the most widely remedies for a broad range of nematodal in humans, cattle, pigs, sheep, and
SURPRISES The first indications that tetramisole and levamisole, when used in field conditions, did more than merely kill nematodes came from a variety of independent, and at first sight, unrelated observations. (1)Beagles
at Janssen
Pre-weaning mortality of the beagles in our colony traditionally averaged about 1/4, despite vaccination, vigorous hygiene, and deworming with piperazine. Pups generally died with symptoms of distemper, atrophy of the thymus, and toxacara larvae in various tissues. After tetramisole was found to have larvicidal activity, it was used instead of piperazine for deworming the bitch before whelping. One year later, only 1/10 of the pups died before weaning, and the year thereafter only 1/20 of the pups died. Transplacental toxocara infection disappeared. Atrophy of the thymus and distemper were no longer observed. Whether the larvicidal drug was active as an adjuvant, boosting the efficacy of the distemper vaccine, was questioned. (2)
African
School
Children
Mass treatment (one 50-mg tetramisole tablet every 3 months during a 2-year period) of African school children who lived in a highly contaminated environment led to a progressive decline in the incidence of roundworm, hookworm, and threadworm in the population that was treated. This decline suggests a beneficial effect of tetramisole on host-defense mechanisms.1 (3)
From the Janssen Research Foundation, Address for reprints: Paul A. J. Janssen, Foundation, B-2340 Beerse, Belgium.
PhD
Cattle
in
Chad
In Chad,
Provost
to increase
the
observed resistence
that in cattle
tetramisole against
seemed contagious
LEVAMISOLE
AND
abortus
OH CH,
R 6438
R 8141
0
\/ (‘)-(S) H’
NTS
Levamisole
Dexamisole
)
Tetramisole
Figure.
From
bovine
zero
to an active
in South
Sheep
In South chlamydial worming tion).
reduced
(personal
and
Pigs
In Australia,
Goodman
tion
weight
of
body
of de-
in Australia noted in
a sudden
tetramisole-treated
normaliza“poor-
doing” calves and pigs. This fect was apparently unrelated (personal communication).
puzzling beneficial efto worm problems
(6)
in Hawaii
In the
Antwerp
Zoo
genic (5)
and
reported
EXPLAINING
by
Fisher
THE
DISTINGUISHED
SERVICE
11
cytoreductive
days
later.
therapy,
B.
as
little or no effect subjects.124 Skin is boosted by
than
SURPRISES
AWARD
ADDRESS
normal
was
on antibody delayed hythe drug in
a variety by anergy
levels
all
CLINICAL
of those
action of tetrain worm-free
conditions,
depressed but
does
of diseases that or immunologic
TWO
possibly
similarly.17’18 of experimental
not
function stimulation
of to
occur.19-23
and many other similar observations, and hypotheses strongly suggested should be active in the treatment
In 1971, a large-scale started to empirically
in Hawaii.
to show the mechanism
react variety
normalized the and T-lymphocytes,
All of these considerations, that levamisole
caused deficiency.
FACES clinical test the
human
caused
are
or
diseases
systemic bacteria;
membranes,
OF LEVAMISOLE research effect
that
accompanied
infections
eyes,
that
program of levamisole
are by
respiratory
are
of
or accompanied
was in
definitely anergy
or or
paired cellular immune mechanisms.24 In summary, levamisole was effective not against various nematodal infections in humans animals, but also in the following four areas: 1. recurrent and chronic infections of the mucus
(1) The first experiment misole on a host-defense
stimulation In a wide
levamisole phagocytes
THE
In the Antwerp Zoo, Thienpont observed apparent cures after treatment with levamisole in ruminants and monkeys that were affected with herpes-like viral infections. Similar observations in monkeys were
killed
anergic patients with various malignant or other diseases such as leprosy.1416 Apparently, healthy elderly patients with reduced skin reactivity to anti-
Africa
Africa, Leroux noted a striking decrease infections in sheep after routine with tetramisole (personal communica-
Calves
by
(4) Levamisole has production in healthy persensitivity, however,
communica-
more
(5)
and
shown by Mike Chirigos in Bethesda.67 This effect of levamisole on stabilization of tumor remission has been observed in several models, including various leukemias, carcinomas, and sarcomas.8”
compound.
pleuropneumonia
organisms,
abortus organisms were grown from the spleens of these vaccinated mice, which indicated that they were incompletely protected against the challenge. However, when tetramisole was given 2 days after the B19 vaccine, the animals were fully protected.23 (2) Fischer showed that levamisole dramatically enhances immunologic protection against various bacterial and viral pathogens in suckling rats and suggested that the drug may be useful in the management of various infections in patients with impaired or immature immunity.45 (3) Levamisole has little or no effect on primary growth and dissemination of experimental tumors, but it can prevent relapse when the tumor mass is first
tion). (4)
TREATMENT
animals was published in 1971 by Renoux.2 Mice were vaccinated with antibrucella vaccine Big, challenged 42 days later with virulent Brucella
0 II N-C-CH, -CH
CANCER
caused
tract,
by
im-
only and skin,
as well
viruses
as
or
397
JANSSEN
TABLE I Controlled
Clinical Studies with Levamisole
First Author (Reference)
As An Adjuvant
Number Cancer
Basic Therapy
(25) KlefstrOm (26) Hortobagyi (27)
Breast Breast
Radiotherapy Cytostatics
Breast
Cytostatics
Stephens
Breast
Cytostatics
Lung
Surgery
Lung Lung Lung Head and neck Larynx Gastrointestinal Cob-rectal
Surgery + BCG Radiotherapy Cytostatics Surgery Surgery + radiotherapy Surgery Surgery
Rojas
(28)
Amery (29) Wright (30) Pines (31) Chahinian (32) Wanebo (33) Mussche (34) Miwa (35) Verhaegen (36) *
Patients
receiving
In Cancer Treatment
t+
levamisole;
= statistically
significant
difference in favor of levamisole;
2. postviral anergy, i.e., the slow recovery period after influenza, measles, characterized by prolonged physical and psychic asthenia; 3. rheumatic diseases, such as rheumatoid arthritis; and 4. in cancer patients, after apparently successful surgery, radiation therapy, or chemotherapy, but in whom relapse rate is high. As shown in Tables I and II, the results of 23 different controlled clinical studies with levamisole as
= not
of Patlents* (Start)
Effectf
20 49 114
+
29
+
96 46 33 24 26 12 143 30
+ ?
+ +
+
+ + +
evaluable.
an adjuvant in the treatment of 13 different types of cancer have been published. In 12 studies, levamisole was significantly superior to placebo (P < .05). In four studies, a statistically insignificant trend in favor of levamisole was reported. In two small trials, no difference with placebo was seen, and the results of the remaining five studies are not evaluable for various technical reasons. General scepticism prevailed, however, for more than a decade until, in 1989, a report that suggested a
TABLE II Controlled
Clinical Studies with Levamisole
Author (Reference)
As An Adjuvant
Number
First
Valdivieso
Cancer
(37)
Gonzalez (38) Hall (39) Takakura (40) Smith (41)
Debois (42) Vuopio
(43)
Brincker
Patients
receiving
Basic Therapy
levamisole;
S
J Clln Pharmacol
Effectf
Cytostatics Surgery
19 103
Melanoma
Cytostatics
60
Brain Bladder Various AML + ALL
Surgery + radiotherapy Surgery + radiotherapy Radiotherapy
31
?
33
(+)
186
(+)
Cytostatics Cytostatics Cytostatics
31 12 111
+
30
(+)
t+
statistically
Cytostatics
Cytostatics significant
difference
in
1991;31:396-.400
-
+
(+)
-
+
35 favor between
398
of Patlents* (Start)
Colo.rectab Melanoma
AML ALL ANLL NH lymphoma
(44)
Pavlovsky (45) Chang (46) Cabanillas (47) *
in Cancer Treatment
of levamisole; levamisole
(+)
= trend
and control;
?
in favor
= not
? of levamisole;
evaluable.
-
= no
difference
LEVAMISOLE
AND
possible benefit from the use of levamisole, alone or in combination with 5-fluorouracil (5-FU), as adjuvant therapy for colorectal cancer in Dukes’ stage B2 (invasion of serosa or pericolonic fat) or stage C (metastasis to regional lymph nodes) appeared from the North Central Cancer Treatment Group.48 These results were promising enough to justify a larger and more definitive study, which involved 1296 patients with resected colon cancer that either was locally invasive (stage B2) or had regional nodal involvement (stage C), by the Eastern Cooperative Oncology Group, the North Central Cancer Treatment Group, the Southwestern Oncology Group, and the Mayo Clinic.49 After a median follow-up time of 3 years for the patients with stage C disease, treatment with levamisole (3 X 50 mg daily for 3 consecutive days every second week) plus 5-FU reduced the risk of cancer recurrence by 41% (P
