The thalidomide tragedy of the 1950s-60s resulted in nearly 10,000 birth defects worldwide after the drug was prescribed to pregnant women for morning sickness. While the German drug company Grünenthal initially denied responsibility, they later apologized and set up victim compensation funds. Extensive research since has proposed several mechanisms for thalidomide's teratogenic effects, including oxidative DNA damage and inhibition of growth factors important for limb development. The actions of Dr. Frances Kelsey at the FDA helped prevent a similar tragedy in the United States by delaying thalidomide's approval until risks were known.

1. Heather Goodwin and Bridget Schwartz
12/7/2012
Final Exam
The Thalidomide Tragedy
Nearly a half decade later, patients who suffered due to the horrific effects of the drug
thalidomide, finally received the first public apology from the German drug company,
Grünenthal Group, that lead to the birth defects of nearly 10,000 children in at least 46 countries
worldwide before its discontinuation (1). Grünenthal Group is a family owned private
pharmaceutical company that marketed thalidomide during the 1950s and 60s during the post
WWII era. The drug was first synthesized in 1954 as a sedative and was thought to be a cure for
insomniacs (2). It was quickly discovered that it could be used for the treatment of nausea and
began to be marketed to pregnant women for alleviating morning sickness. A few short years
later, doctors began to notice abnormalities in several children and began linking it to mothers
taking thalidomide. By 1961 the drug was taken off the market in most countries, but not after
countless suffered. Thalidomide is still prescribed in the United States under strict regulations for
both multiple mylenoma and leprosy.
When thalidomide was initially approved there were no regulations in place that required
drugs to be fully tested for safety. Thalidomide is a white crystalline, odorless compound with
low solubility in water (2). It was found to be nonfatal in overdose, in addition to testing done in
rats where its potency was established as nontoxic so toxicity in higher mammals was not
expected (2). These two things were enough to prove efficient safety at the time. In addition,
during this time, physicians believed that no drugs crossed the placenta, deeming all medications
an expectant mother took to be safe to the fetus. Teratogenic effect, the ability to develop

2. abnormalities in the fetus, was also not well studied as no drugs were tested in pregnant animals
(3). The lack of testing allowed thalidomide in a sense to slip through the cracks in the post-
WWII era of propaganda.
A wide array of pharmaceutical companies then began to manufacture the drug under
several trade names with the primary distribution seen in Europe, Australia, and Japan (4).
Advertisements for thalidomide claimed that the drug was helpful in treating anxiety, insomnia,
gastritis and tension. The number one claim however was that it was “safe and harmless” for
pregnant women as an antiemetic (3). Marketing began in Germany where it was sold without a
prescription (5). Miller and Strömland (2) report that by 1960 production of thalidomide reached
14.58 tons.
By 1961 there were several doctors that began to notice the rare birth defects associated
with thalidomide exposure. Dr. William McBride first noticed the cases at Crown St. Women’s
Hospital in Sydney, Australia where he practiced as an obstetrician. He immediately notified the
hospital to stop using the drug and wrote a letter to Distillers, the distributer of the thalidomide
(“Distaval”) in Australia (3). Around the same time, a pediatrician and geneticist in Germany,
Dr. Widukind Lenz, was beginning to note similar cases. In a lecture given by Dr. Lenz in 1992,
he states that he first suspected the thalidomide as the cause for the birth defects on November
11, 1961 and after 5 days of continuing investigation he phoned a warning to Grünenthal Group
on the 16th. Lenz reports that it took ten days of discussions with representatives and health
authorities before the drug was withdrawn (5). However as seen on the Contergan website (the
brand name given to thalidomide in Germany), they discuss that the first reports of negative side
effects were brought to their attention in October of 1959. They then applied for prescription-
only status and 6 months later Dr. Lenz began his crusade against the drug company. Despite

3. thalidomide being taken off the market, some countries continued to distribute it for several
months; Canada being the last country to finally pull it off the market in 1962. Despite the drug
being pulled, Grünenthal Group continued to deny any teratogenic effect for many years.
Independent research from both Dr. McBride and Dr. Lenz helped to hone down on the
defects seen in the children affected. The most frequently reported cases were limb defects
ranging from muscle aplasia to triphalangeal thumbs (2). However there were also the striking
anomalies consisting of absent or hypoplasic limbs; this was followed by malformations of the
inner and outer ear leading to deafness, ocular abnormalities, malformations of the heart (leading
to congenital heart disease), the bowel, the uterus, and the gallbladder (4,5). Due to the large
number of women who took the drug, it was quite easy for researchers to establish a correlation
between intake and resultant malformations. By looking at the exact date of intake along with the
number of pills taken, they could put together an accurate timeline of when the different
malformations occurred. Thalidomide was found to be different than many other teratogens in
that time of intake was the predominant factor as opposed to clinical dosage since the drug is so
rapidly hydrolyzed (2). Based on the research done, it was established that the most sensitive
times for the development of malformations from thalidomide were between the 34th and 50th
day after the last menstrual period (20-36 days post-fertilization) (2). Miller and Strömland (2)
state that anotia, “no ear,” was found at the beginning of the sensitivity, followed by thumb
aplasia, upper extremities, lower extremities, and lastly triphalangeal thumbs. While not listed in
a specific time frame, dental malformations, autism, mental retardation and Duane syndrome
(lack of the sixth nerve and aberrant innervation of ocular muscles by the third cranial nerve) are
also findings in thalidomide-exposed children (4).

4. The thalidomide tragedy revealed that the placenta was pervious to drug molecules
ingested by the expectant mother (3). Before this, researchers and physicians believed that the
fetus was fully projected from drug ingestion, unless the mother was killed as a result of use.
This new discovery highlighted the fact that fetal drug exposure must first be studied in animal
models before it is prescribed to expecting women or women who may become pregnant. In
addition, this new discovery lead to numerous research studies aimed at understanding the
mechanisms of thalidomide and its teratogenic capabilities.
Regardless of the substantial amount of research performed since the drug’s withdrawal
in the 1960s, the exact mechanism of thalidomide teratogenesis remains unclear (6). However,
the mechanisms of other closely related teratogenic drug molecules are known and have served
as a starting point for Thalidomide research. Many of these related molecules are known to cause
DNA damage through oxidative stress (6). During drug metabolism, these drug molecules
interact with prostaglandin H synthase (PHS) to form free-radical drug intermediates. The free-
radical intermediates produce reactive oxygen species (ROS), which oxidize DNA and damage
fetal developmental tissues (6). In a 1995 study, Liu and Wells provided evidence that
Thalidomide behaves similarly and that the teratogenicity of the drug involves some form of free
radical-mediated oxidative damage to developing embryonic macromolecules (7). They revealed
that horseradish peroxidase plays a role in thalidomide bioactivation and that the drug
intermediates produced have the capability to oxidize DNA, and ultimately embryonic tissues.
(7). Furthermore, Arlen and Wells demonstrated that the administration of acetylsalicylic acid, a
PHS inhibitor, into thalidomide treated rabbits was able to reduce the degree of teratogenicity
observed (8). This provided further evidence that oxidative stress played some role in the
developmental issues seen in so many children.

5. In the May of 1999, Parmen et al. further assessed the involvement of ROS, as a result of
free-radical formation, on thalidomide teratogenicity in pregnant rabbits. Researchers divided the
rabbits into three different treatment groups. Group one received a saline placebo serving as the
control group. Group two first received an intravenous injection of saline followed by a
400mg/kg dose of thalidomide (6). The last group was pretreated with 40mg/kg dose of alpha-
phenyl-N- t-butylnitrone (PBN), which has been successfully used to trap free radical drugs in
mice treated with teratogenic anti-convulsant drugs, such as phenytoin (6). These rabbits were
then administered the same 400 mg/kg thalidomide as rabbits in group two. The rabbits were
killed, embryos were explanted, and tissues from the liver, lung, brain, kidney, and placenta of
the mother were extracted. The level of thalidomide initiated DNA oxidation was studied by
extracting DNA after treatment and measuring the amount of the oxidized guanosine analog, 8-
OH-2’-dG, in both the mother and embryos (6).
Parmen et al. found that pretreatment with PBN reduced DNA oxidative stress in all
maternal tissues and embryos by approximately 73% (6). No birth defects were found in the
control group and very few were observed in the PBN pre-treated group. Fetuses from the
thalidomide group had a 35% chance of phocomelia, or absence of the proximal limbs, 10%
chance of omphalocele, or protrusion of the intestine into the umbilical cord, and a 10% chance
of adactyle, or absences of the fingers and toes (6). Researchers concluded that thalidomide
increased the incidence rate of fetal resorption by 450% and postpartum fetal lethality by 780%
(6). The pre-treatment of rabbits helped reduce the incidence rate of fetal deformities and fetal
resorption by 73%, and fetal lethality by 56% (6). This study provided an abundance of evidence
that the teratogenicity of thalidomide is a result of the drug’s bioactivation to a free-radical
intermediate that has the ability to cause embryonic DNA oxidation.

6. In 2000, Stephens et al. revealed another plausible mechanism for thalidomide
teratogenicity other than DNA damage caused from the production of ROS; his mechanism came
from free-radical intermediates during drug metabolism. These researchers proposed that the
deformities observed in embryos are a result of disruptions of the insulin-like growth factor I
(IGF-I) and fibroblast growth factor 2 (FGF-2). Both are involved in the activation of the αvβ3
cell surface integrin dimer, which stimulates angiogenesis in developing limb buds during fetal
development (9). The promoter regions of IGF-1 and FGF-2, and αvβ3 genes lack TATA boxes,
but contain numerous GC boxes instead (9).Thalidomide is capable of specifically binding to the
GC box and inhibiting or decreasing the transcription potential of these genes (9). Stephens et al.
proposed that once the transcription process is disrupted, angiogenesis capability is
compromised, and physical deformities of thalidomide-exposed offspring are likely.
More recently, in 2010, Ito et al. proposed that thalidomide affects embryonic limb
development by binding to cereblon, an important protein for limb formation (10). These
researchers first performed affinity purification to identify and purify thalidomide-binding
proteins. They found that thalidomide specifically binds to cereblon (CRBN), which results in a
uniquitin ligase-complex with damage DNA binding protein 1 (DDB1) and Cul4A (10). The
formation of the ligase-complex between these proteins is important for limb outgrowth and
development. By using both chicks and zebra fish, Ito et al. utilized numerous genetic techniques
to reduce and inhibit the formation of the cereblon ligase complex with DDB1 and Cul4A (10).
In doing so, researchers observed fin and otic vesicle deformities comparable to other embryos
treated with thalidomide. Since zebra fish and human cereblon are approximately 70% identical
(4), researchers propose that the primary mechanism for researchers propose that the primary

7. mechanism for thalidomide teratogenicity is the binding of the drug to an important
developmental protein.
Since 1966, there have been over 30 proposed mechanisms for thalidomide teratogenicity
and even more attempts to understand the devastation caused by the drug’s administration to
pregnant women. Research has supported acylation of macromolecules, ascorbic acid synthesis,
down regulation of adhesion receptors, alteration of cytokine synthesis, folic acid antagonism,
inhibition of DNA synthesis, DNA oxidation, interference of glutamate metabolism, and
mesonephros-stimulated chondrogenesis as potential and likely causes of the embryonic
deformities (4). Not enough evidence has been provided to rule out some these mechanisms, nor
prove that one is the exact cause. However the hypotheses of oxidative stress, DNA intercalation
into GC boxes, angiogenesis inhibition, and celebron binding have the most evidence, so they
seem more likely (4). As revealed by Kim and Scialli, it is possible that a combination of
proposed mechanisms are the true cause of teratogenicity (4).
Before all the mechanisms were known, Grünenthal Group denied all claims that they
were responsible for any of the issues that arose during the thalidomide outbreak. Even more,
they continued to deny the claims for years later as well after light began to be shed on the
issues. However many accusations against the company began as early as 1961. The main case
against the company opened on May 27, 1968 and ended on the 18th of December, 1970 with 9
Grünenthal executives and research employees defending the company (11). Victims set out to
be compensated for their suffering, which many to this day still are not adequately compensated.
Most victims received a one-off capital sum depending on the severity of their disability in
addition to a life-long monthly pension (11). However not all the victims in the countries the
drug was distributed to were covered under this. Canadians for instance had to fight to get a

8. minute lump sum under the "Extraordinary Assistance Plan" established by the Ministry of
National Health and Welfare (now Health Canada) in 1991. In Germany, the Federal
Ministry of Health established the Disabled Children’s Relief Foundation Act (“Hilfswerk fuer
behinderte Kinder”) in November 1971 (5). This act was intended to provide assistance to all
children with disabilities, but the purpose was foremost to provide benefits to the thalidomide
victims. Grünenthal Group paid 114 million deutschmarks (DM) into the foundation. This came
from both the company and the owners, the Wirtz family. The German government also paid
DM 100 million into the foundation with half of all the funds being delegated to the thalidomide
victims (11). In 2008 another DM 50 million was deposited into the foundation by Grünenthal to
help improved the financial situation of the victims. Many thalidomide victims now in their 40s
and 50s are still fighting their cases to get the money they feel is rightly theirs. As one victim
commented after the public apology by Grünenthal Group, “…when you are disabled, it costs a
lot of money. We are in our 50s, we need care. We need adaptations in our houses and cars, for
starters. So if they’re serious, let’s get around the table and talk financial help” (1).
There was a completely different story going on in the United States thanks in part to one
person, Dr. Frances Kelsey. Dr. Kelsey was a member of U.S. Food and Drug Administration
(FDA) and put a hold on the approval of the drug. She did this before thalidomide was even
proven to be linked to the birth defects, but because of her own concerns about peripheral
neuropathy, which had been seen as a side effect in patients and can be sometimes irreversible, in
addition to the potential effects that biologically active drug such as this could have after
treatment in a pregnant woman (4). Kelsey went about requesting data from Grünenthal insisting
that they were not being completely honestly; describing the material being sent as
“pseudoscientific jargon” (12). This went on for quite some where hard facts were demanded by

9. Dr. Kelsey and not provided despite Grünenthal complaining. The FDA continued to stand by
her until 1961 when the birth defects would finally be linked to thalidomide, thus resulting in
Grünenthal withdrawing their application for FDA approval (12).
An unknown number of American children were still at risk for thalidomide malformations due
to woman acquiring the drug from illegal means. In addition to the US children now affected the
world was abuzz with the tragedy that had plagued so many. A public outcry ensued resulting in
Congress getting involved. The Kefauver-Harris Amendment was made to the 1938 Food, Drug
and Cosmetic Act and helped to represent a revolution in FDA regulatory authority where they
were previously lacking. The legislation gave the FDA the power to demand drug companies to
provide proof that their products were both safe and effective before they received approval to be
marketed in the United States (13). Prior to this amendment, drugs could be sold 60 days after
companies filed with the FDA if they did not object. Drug makers therefore routinely sent their
new medication to doctors to “try out” their new products, which was the case with thalidomide
(13).
After this law passed, 5 new branches were created in the FDA, one of them being the
Investigational Drug Branch that Kelsey became the head of. Kelsey went on to draft new
regulations for investigational drugs, which includes the establishment of 3 phases of clinical
research, now used around the world (13). As big of a tragedy as the thalidomide outbreak was, it
helped to change the world of drug regulations for the better. Laws were passed worldwide to
ensure better safety for all. A system was put in to place for post-market drug surveillance. This
ensured that once a drug was on the market, monitoring for any new side effects takes place and
are reported through the physician (3). By having this system in place, countless lives have been
saved as a result of drugs being pulled of the market due to safety issues. These stricter

10. regulations have changed the drug market in ways that cannot otherwise be fathomed if not in
place.
Regardless of the unknown mechanism for toxicity and strict regulations, thalidomide is
still used to treat a variety of diseases and disorders. The ability of thalidomide to affect and
decrease angiogenesis has proven useful in the treatment of leprosy and some cancers, such as
multiple myeloma. Individuals with leprosy commonly develop vasculitic nodules, which
develop as a result of underlying problems with blood vessels (4). The administration of
thalidomide to these patients has shown to suppress vasculitic nodule development and the
severe pain associated with their presence (4). Thalidomide’s anti-angiogenesis capabilities have
also proven useful for treated patients with certain cancers. Lenalidomide, a thalidomide analog,
is currently used in the treatment of multiple myeloma. The drug, like thalidomide, is able to
prevent or slow metastasis by inhibiting the leaky vasculature associated with tumor growth (4).
A 2007 study, demonstrated that the analog was still as effective, but only caused embryonic
deformities when a maternally toxic dose was administered (4).
Lastly, thalidomide has been useful in the treatment of wasting syndrome in patients with
advanced HIV. The syndrome is characterized by unintended weight loss and a substantial
increase in interleukin-6 and tumor necrosis factor-α (TNF- α) cytokines (14). Thalidomide’s
ability to inhibit the synthesis of TNF- α has shown to prevent or slow the progression of the
syndrome, thus prolonging life for infected individuals (4).
Even though thalidomide was responsible for much devastation in the 1950s and 1960s,
its therapeutic abilities for these diseases and disorders cannot be ignored. As a result, the drug
is available, but not without strict FDA guidelines and regulations. The Celgene Corporation,

11. the drug manufacture of thalidomide, has since developed System for Thalidomide Education
and prescribing Safety (STEPS) program in order to prevent the drug’s distribution and exposure
to pregnant women (4). This program requires that all physicians who prescribe Thalidomide to
educate their patients on both the potential benefits and side effects of the drug. The physician
must also be registered within the program to keep tract of the drug’s distribution. In return the
patients must agree to contraceptive counseling, regular pregnancy testing, and informed consent
before receiving the drug (4). Female patients must use two forms of birth control when being
treated with thalidomide. Furthermore, physicians may only distribute a 4-week supply, without
automatic refills. If any of these steps and regulations are not followed, prescriptions will not be
honored or filled at the pharmacy (4). The development of the STEPs program has prevented
thalidomide teratogenicity in the United States, however developing countries remain at risk (4).
In conclusion, the thalidomide tragedy has changed the field of pharmaceutical science in
numerous ways since its withdrawal in the early 1960s. Still today, individuals are living with
deformities that resulted because accurate research was not preformed before their mothers were
exposed to thalidomide. Nearly 60 years later, the exact cause of teratogenicity remains unknown
regardless of the 30 proposed mechanisms and countless research studies. Even still, the drug has
proven useful for numerous diseases associated with angiogenesis and inflammation, and is still
currently available, with strict FDA regulations.

12. ______________
1. Burns, John F. "German Drug Maker Apologizes to Victims of Thalidomide." The New York
Times 2 Sept. 2012: A4. Print.
2. Miller, Marilyn T., and Kerstin Strömland. "Teratogen Update: Thalidomide: A Review, with
a Focus on Ocular Findings and New Potential Uses." Teratology 60.5 (1999): 306-21. Print.
3. McBride,W. G. ‘‘Thalidomide and Congenital Abnormalities.’’ The Lancet 2 (1961):1358.
Print.
4. Kim, James H., and Anthony R. Scialli. "Thalidomide: The Tragedy of Birth Defects and the
Effective Treatments." Toxicological Sciences 122.1 (2011): 1-6. Print.
5. Lenz, Widukind, Dr. "The History of Thalidomide." Lecture. 1992 UNITH Congress.
Thalidomide Victims Association of Canada. Web. 28 Nov. 2012.
6. Parman, T., Wiley, M., and Wells, P. “ Free Radical-mediated oxidative DNA Damage in the
Mechanism of Thalidomide Teratogenicity. Nature Medicine. 5, 582-585. Web. 29 Nov.
2012
7. Liu, L. & Wells, P. “DNA Oxidation as a Potential Molecular Mechanism Mediating Drug-
Induced Birth Defects: Phenytoin and Structurally Related Teratogens Initiate the Formation
of 8-hydroxy-2’-deoxyguanosine in vitro and in vivo in Murine Maternal Hepatic and
Embryonic tissues. “Free Radic. Biol. Med. 19, 639–48 (1995). Web. 29 Nov. 2012.
8. Arlen, R.R. & Wells, P.G. “Inhibition of Thalidomide Teratogenicity by Acetylsalicylic acid:
Evidence for Prostaglandin H synthase-catalyzed Bioactivation of Thalidomide to a
Teratogenic Reactive Intermediate”. J. Pharm. Exp. Ther. 277, 1649–58 (1996). Web. 29
Nov. 2012.
9. Stephens, T.D, Bunde, C.J., and Fillmore, B.J. “Mechanism of Action in Thalidomide
Teratogenesis.” Biochem Pharmacol. 12 1489-1499 (2000). Web. 29 Nov. 2012.
10. Ito, T. et al. “Identification of a Primary Target of Thalidomide Teratogenicity.” Science 327
1345-1350 (2010). Web. 29 Nov. 2012.
11. The Foundation." Contergan.com. Grünenthal, 2012. Web. 29 Nov. 2012.
<http://www.contergan.grunenthal.info/grt-ctg/GRT-
CTG/Die_Fakten/Die_Stiftungsloesung/152700067.jsp;jsessionid=F776062BBF10A33421A
E8913EC092B0C.drp1>.
12. Kuehn, B. M. "Frances Kelsey Honored for FDA Legacy: Award Notes Her Work on
Thalidomide, Clinical Trials." JAMA: The Journal of the American Medical Association
304.19 (2010): 2109-112. Print.
13. "50 Years: The Kefauver-Harris Amendments." US Food and Drug Administration. US
Department of Health and Human Services, 20 Nov. 2012. Web. 29 Nov. 2012.
<http://www.fda.gov/Drugs/NewsEvents/ucm320924.htm>.
14. National Institute of Allergy and Infectious Diseases. “HIV Wasting Syndrome.” National
Institutes of Health. (1997). Web. 29 Nov. 2012. <http://aidsinfo.nih.gov/news/362/hiv-
wasting-syndrome/>