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OCR for page 30
-
The Current Status of
Contraceptive Research
Since the introduction of the pill and the IUD in the early 1960s, no
fundamentally new contraceptive methods have been approved for use in the
United States. This chapter discusses the new contraceptive methods currently
being studied both in the United States and abroad. We try to provide an
overview of promising scientific leads, and thus of methods that the public might
reasonably expect to be available within the next 10 to 15 years. Unfortunately,
such a general criterion is hard to apply without dispute. One person's promising
new development is, for another, a preposterous idea or only a trivial modification.
We have chosen to be inclusive rather than exclusive, since our aim is to provide a
sense of what might be possible if the barriers to faster development were
reduced. We have also included a brief overview of important modifications of
existing methods to enable readers to evaluate more knowledgeably the range of
potential innovations that changes in public policies could yield.
RESEARCH LEADS
Dramatic changes in the range of available contraceptive technology are unlikely
to occur in the 1990s (Djerassi, 1987; Harper, 1983~. Most of the contraceptive
methods that will be available in the United States between now and the turn of
the century will constitute modest improvements to existing methods. So, although
no single new contraceptive will be a panacea for the fertility control needs of all
people, scientists are studying a number of promising leads that could result in the
development of contraceptives that have few side effects and health risks and are
more effective, more easily administered and used, and less costly.
30
OCR for page 31
CURRENT STATUS OF CONTRACEPTIVE RESEARCH 31
The acceptability of new methods or of modifications of existing methods
among potential users and their effect on nonuse are difficult to predict. Advocates
of new technology often exaggerate the potential impact of Innovations, while
critics of new methods often underestimate the likely influence of such changes.
Modest improvements in existing methods will probably not significantly increase
acceptability and use. But major changes, such as that made possible by a
contraceptive implant, could substantially increase the acceptability of contraceptive
practice.
It is extremely difficult to estimate when a particular new contraceptive will be
available. The entire development process is surrounded by the uncertainties of
scientific research, funding, marketing feasibility, and regulatory approval. Based
on a 1980 survey of contraceptive development experts, the congressional Office
of Technology Assessment (OTA) named nine fertility control methods as "highly
likely before 1990" (OTA, 1981~. Only three of these technologies triphasic
pills, the Copper T3 80A intrauterine device, and the Today contraceptive sponge-
were available in the United States as of June 1989. Two steroidal methods, long-
acting injections (e.g., Depo-Provera) and implants (e.g., NORPLANT@), are
available in other countries. (A New Drug Application for NORPLANT~ to be
used in the United States has been feed with the FDA.) Four methods improved
ovulation~etection methods, vaginal rings, luteinizing hormone-releasing hormone
(LHRH), and prostaglandin analogues are being studied but will not be available
in the near future. None of the 11 technologies designated by OTA as "possible
by 1990 but prospects doubtful" is likely to be available for several years, and
some could take an additional decade or longer to be developed or could, indeed,
not be developed at all.
Given the problems encountered in previous efforts to identify the range of
potential new contraceptives, we do not argue strongly for our list of possible
contraceptive innovations. Instead, we want to emphasize that significant
developments are possible and are being studied and that, in some cases, couples
in other countries are already benefiting from new methods not yet available in
the United States. Each new method represents possible improvement over
existing methods, either because of new drugs or materials or because of a more
effective, safer, or more convenient mode of administration. Because some of the
methods being studied use drugs or other substances already approved by the
FDA, the approval process for them may be less cumbersome, time-consuming,
and costly than for a totally new method.
Female Methods
New methods of delivering contraceptive steroids are being evaluated in
clinical trials, and some are expected to be available for general use during the
1990s. These new delivery systems include injections, implants, ~ansdermal
patches (through the skin), vaginal suppositories and rings, and sublingual tablets
OCR for page 32
32 DEVELOPING NEW CO=~CE~~ES
(under the tongue). Because most of the new delivery systems release the drug
into the bloodstream at a constant and slower rate and in smaller doses than
existing oral contraceptives, they may have fewer adverse health effects than the
pill. Such delivery systems are also more convenient for some users than oral
tablets.
In addition to the injectables already available in other countries, new
formulations of injectables using rrucrospheres and nucrocapsules are undergoing
human trials and may become available by the early to mid-1990s, assuming there
are no major problems or delays in clinical testing (Liskin and Blackburn, 1987~.
Similar in concept to time-released cold capsules, these injectables consist of one
or more hormones encased in biodegradable capsules and suspended in a sterile
solution. The capsules release hormones gradually to block ovulation. Depending
on the formulation, one injection can provide contraception for one, three, or six
months. The most promising microspheres contain one of the progestins,
norethindrone WEIR or norgestimate. A disadvantage of this approach is that,
once administered, it cannot be removed or reversed.
Injectable microspheres with NET have been tested in nearly 200 women, and
more extensive clinical trials are under way (Beck and Pope, 1984; Rivera et al.,
1984; Liskin and Blackburn, 1987~. The pregnancy rate is expected to be similar
to that of oral contraceptives, but the incidence of side effects may be lower.
Irregular menstrual bleeding and the absence of menses are the main side effects
found in the clinical trials to date.
Two formulations of progestin-estrogen combination once-a-month injectable
contraceptives have been developed by the World Health Organization's Special
Programme in Human Reproduction. A large Phase III multicenter study has
been completed and has confirmed their high efficacy as well as the regular
vaginal bleeding patterns associated with their use. Plans are being made for
introductory field studies in Latin America and Southeast Asia.
Biodegradable pellets are similar to the new spastic contraceptive implants
(see below), in that they are a long-acting, slow-release contraceptive. But unlike
the implant, the pellets can be removed only within the first few months of
insertion. The rice-size pellets, which are inserted under the skin in the hip or
-upper and, slowly release progestins, thereby inhibiting conception. The pellets
themselves are absorbed while the hormones are being released. The two types of
pellets currently undergoing clinical trials are effective for one to one and a half
years. The main side effect identified to date is irregular menstrual bleeding,
particularly in the first few months of use (Program for Applied Research on
Fertility Regulation, 1985~. It is estimated that they could be available for general
use in the mid-199Os. The inability to remove the pellets, once administered, is a
disadvantage.
The vaginal ring consists of a silicone rubber ring about the size of a diaphragm
that continuously releases steroids to suppress ovulation and thicken the cervical
mucus, thereby preventing sperm from entering the uterus. Vaginal rings have the
OCR for page 33
CURRENT STATUS OF CONTRACEPTIVE RESEARCH 33
advantage of being user-controlled and readily reversible. Depending on their
formulation, vaginal rings are worn continuously for three months and then
replaced, or for three weeks at a time and then removed for one week to allow
monthly bleeding. The rings may be removed for a few hours without reducing
their effectiveness and do not need to be in place during intercourse (Harper,
1983~. Vaginal rings do not need to be specially fitted, but f~rst-time users should
be screened and instructed in proper use.
Research is most advanced on a continuous-wear vaginal ring containing
levonorgestrel, the same progestin used in some oral contraceptives. However,
the pregnancy rate observed in clinical trials of the ring was higher than that of
oral contraceptives. In one Dial involving about 1,000 women, there were 3.5
pregnancies per 100 woman-years of use (WHO, 1985b). Similar to other
progestin-only methods, the main side effect associated with the levonorgestrel
vaginal ring is irregular menstrual patterns. Clinical trials have been completed,
and an application for marketing approval in the United Kingdom has been
submitted. Introductory studies are expected to follow validation of the ring's
manufacturing process. Other vaginal rings containing progesterone and both
progestins and estrogens are being tested. Some experts estimate that these other
rings may be available in the early 1990s. The progesterone ring could be very
useful for breastfeeding women, because it would not affect breast milk.
Transdermal patches constitute another delivery system that could provide
slow, consistent release of contraceptive steroids to the bloodstream through the
skin. Now being used to provide estrogen-replacement therapy to menopausal
women, the transdermal patches can be worn on the body and replaced by the user
as needed (ALZA Corporation, 1988b). In one system, three patches (each
effective for seven days) would be worn consecutively for three weeks, followed
by a week during which no patch or a placebo patch would be worn to allow
menstrual bleeding to occur. Early clinical teals of this system were completed in
1988 and studies on improved patches were scheduled to begin in the United
States in 1989.
The technology of osmotic pills could also be used for controlled release of
contraceptive steroids. Osmotic pills allow for a gradual release of a drug encased
in a semipermeable membrane. Because the drug is released continuously at
controlled rates, lower and less frequent dosages are possible, thereby reducing
the potential adverse effects associated with oral formulations that are absorbed
quickly (ALZA Corporation, 1988a).
Many researchers believe that, in the long term, a vaccine could be the ideal
contraceptive because it could be highly effective, long-acting, and eventually
reversible. Three types of vaccines are currently being studied. One would
immunize a woman against human chorionic gonadotrophin (hCG), a placental
hormone that is needed in early pregnancy; the second would immunize against
the hormone in the zone pellucida of the egg; and the third would work against the
sperm (Harper, 1983a). Following an initial series of injections to establish
OCR for page 34
34 DEVELOPING NEW CO=~CE~~ES
.
immunity, a woman would need a periodic (probably annual) booster shot to
prevent the return of fertility. Research on vaccines is at an early stage, and there
are many technical problems to overcome. Nonetheless, it is possible that at least
one version of the hCG antipregnancy vaccine could become available for use in
some countries around the turn of the century (Segal, 1989~. In 1988 the FDA
approved the initiation of clinical research on a contraceptive vaccine in the
United States.
One alternative to the contraceptive methods based on analogues of estrogen
and progesterone is the use of luteinizing hormone-releasing hormone (LHRH)
analogues, which control reproduction by affecting the pituitary gland (Schally et
al., 1971; Guillemin et al., 1971~. In early clinical trials, LHRH analogues have
been effective in suppressing ovulation, and ovulation returned quickly once the
drug was discontinued (Eloper, 1983~. It was originally thought that LHRH
analogues could be administered by injection or nasal sprays; other possible
modes of administration include suppository, cheek insert, or oral capsule (OTA,
1981~. Researchers believed that LHRH analogues might have fewer side effects
than combined oral contraceptives. However, clinical work has revealed many
difficulties. LHRH analogues also block production of estrogen and progesterone
in the ovaries; if these hormones are replaced by drug therapy, the resulting side
effects might negate any advantages LHRH analogues have over existing steroidal
methods (Wiedhaup, 1988~.
Male Methods
Although sperm antigens have been tested for use in women, their use in a
reversible vaccine for men is not considered feasible because destroying sperm
production capability would lead to permanent sterility (Harper and Sanford,
1980~. Animal studies using sperm antigens found an increase in tumors in male
mice and more atherosclerosis in male monkeys (Alexander and Anderson, 1985~.
Because so much more research is needed to develop and test suitable antigens for
a male vaccine, a male vaccine-reversible or permanent will not be available
for general use in this century.
Inhibin, a peptide derived from the testis, is thought to regulate production of
follicle-stimulating hormone (FSH). More research is needed to understand the
biology and to develop the specific form of inhibin needed for sperm suppression
and to develop a specific regimen for its use. Nevertheless, animal studies
suggest that an ESH-inhibiting drug might be effective without changing libido or
potency.
Scientists are also studying ways to interfere with the fertilizing capacity of
sperm as they mature while passing through the epididymis. In the 1960s,
gossypol, a derivative of cotton seed, was found to cause male infertility in China.
Although the rigor and documentation of many Chinese studies of gossypol are
uncertain, the antifertility action of gossypol has been studied extensively and its
OCR for page 35
CURRENT srATUS OF CONTRACEPTIVE RESEARCH 35
effectiveness has been clearly demonstrated. Two major side effects threaten its
potential usefulness: it can deprive the body of potassium (needed for normal
muscle function), and its antifertility effect appears to be irreversible in some
cases. Reduced sperm count can take two to three months to achieve, and the
return of fertility may take at least three to four months (Harper, 1983~. To date,
no clinical studies of gossypol have been initiated in the United States. However,
the principles underlying research on gossypol should enable scientists to explore
other important areas in search of a nonhormonal, nonendocnne contraceptive
method.
Modifications of Existing Methods
Significant modifications of oral contraceptive formulations have recently
been introduced in Europe. Three new compounds-desogestrel, gestodene, and
norgestimate-allow significant reductions in dosage compared with oral
contraceptives currently on the market in the United States (Wiedhaup, 1988~. A
new oral contraceptive containing gestodene, for example, contains only about
one hundredth the amount of contraceptive steroid contained in the first oral
contraceptive marketed in the United States in the early 1960s (Segal, 1989~. If
the European manufacturers file for FDA approval, these new oral contraceptives
may become available in the United States in the l990s.
The main focus of research on natural family planning methods has been
devicesforpredicting ovulation or detecting when ovulation has occurred in order
to pinpoint more accurately the time for periodic abstinence. In some Western
countries, the first models of a "personal rhythm clock," which uses a high-
precision thermometer and calculator to interpret daily fluctuations in body
temperature, and an "ovutimer," which analyzes changes in cervical mucus, are
on the market.
Practical biochemical methods for prediction of ovulation, and therefore for
improvements in natural family planning, can also be anticipated in the l990s.
Research on new monoclonal antibodies, which can be used to detect hormones
produced by the ovary, is far advanced. Reliable detectors for ovulation based on
urinalysis are already on the market. Research is also under way on ovarian
markers of follicular growth and urinary estrogen assays to monitor follicular
development (Institute for International Studies in Natural Family Planning,
1988~. Research has also been carried out on the use of salivary electrolytes and
glucose as an indicator of the fertile period (WHO, 1988~.
New hormone-releasing IUD s and modifications to copperIUDs have recently
been developed and tested (Sivin and Tatum, 1981; Luukkainen et al., 1987~. A
long-lasting copper IUD, which has a pregnancy rate of less than 1 percent, was
introduced in the United States in June 1988. These methods provide highly
effective long-term protection at relatively low cost with little risk for most
women.
OCR for page 36
36 DEVELOPING NEW CO=~CE~~ES
The search for new sperr~ucides, especially those with virucidal properties, has
taken on new importance as a consequence of the dramatic increase in sexually
transmitted diseases. Several researchers are trying to develop new spermicides.
Preliminary studies have found that propranolol, a beta blocking agent widely
used in the treatment of cardiovascular disease, is an effective spermicide. One
study involving 198 volunteers found a pregnancy rate of 3.9 pregnancies per 100
woman-years of use (Sherris, 1984~. However, more work needs to be done on
formulation and on research to increase effectiveness.
Disposable diaphragms containing spermicide have been developed but are
not being vigorously pursued. One disposable diaphragm manufactured by G.D.
Searle and Co. was approved by the FDA in the late 1970s but was withdrawn in
1980 when test marketing sales were low (Sherris, 1984~. The FDA refused G.D.
Searle's request for approval to market the product for sale without a prescription.
GynoPharma is currently evaluating a new vaginal barrier very similar to the
disposable diaphragm.
A female condom, developed in Europe in the early 1980s, is being tested in
both Europe and the United States. Made of polyethylene plastic, the female
condom consists of two flexible rings and a loose-fitting sheath that lines the
vagina so that sperm cannot enter the cervix (International Planned Parenthood
Federation, 1988~. The larger ring at the open end secures the device outside the
vagina, while a smaller ring at the closed end is inserted into the vagina and
placed at the cervix. It is larger than a male condom, its use is controlled by the
female, and the method may provide greater protection against sexually transmitted
diseases.
Recently the FDA Medical Device Center allowed the marketing of two
condoms: the "minicondom," a shorter version of a condom using adhesives (in
1988), and the "panty condom," a condom constructed so that it can be worn by
the woman (in 1987~. Because these products were considered to be substantially
equivalent to products already on the market, no clinical studies of efficacy and
safety had been required for FDA approval. In 1989 the status of both products
changed: before the minicondom can be marketed, pregnancy rates must be
included in the package labeling; and clearance for the panty condom was rescinded
pending FDA reevaluation because of a change in the product's design.
Considerable work is also under way to develop a new type of male condom
that substitutes synthetic materials such as silicone and polyurethane for latex.
These materials could provide greater strength, uniformity, and durability and
increased sensitivity compared with latex products.
Another research lead involves sterilization procedures.
Current female
sterilization procedures can be reversed only through use of complex microsurgery,
which is expensive and not always successful. Researchers have been exploring
various techniques for reversible female sterilization, but there are no major leads
on the horizon. Clips, bands, fimbrial hoods, and plugs to obstruct the fallopian
tubes have been tested, but none has proven to significantly increase reversibility.
OCR for page 37
CURRENT STATUS OF CONTRACEPTIVE RESEARCH 37
Research on transcervical sterilization the placement of various chemicals
into the uterus at the opening of the oviduct has been under way for 20 years.
Such procedures would eliminate the risks associated with surgery, but none of
them has proven very practical. Among the chemicals that have reached the stage
of clinical trials are silver nitrate, quinacrine, phenol, ethanol-formaldehyde, and
methylcyanoacrylate (Harper, 1983~. Most of these chemicals cause scarnng,
which blocks the fallopian tubes. Researchers have also injected liquid silicone
rubber into the fallopian tubes to form a barrier when it hardens. The main
problems with sclerosing agents have been the high failure rates and the need for
repeated installations. These techniques could also pose a greater risk of ectopic
or tubal pregnancy. Reversibility is another concern, although the rubber plugs
may prove to be removable Warper, 1983~.
In recent years, much research has been done on reversible methods of male
sterilization and nonsurgical techniques to make the procedure easier and less
expensive. Various valves and plugs that are inserted into the vas deferens to
block sperm transport have been tested, but it has proven difficult to anchor them
in the vas, and there have been problems with vas erosion and inflammatory
reactions (Harper, 1983~. The"Shug" device, which consists of two silicone
plugs joined by a nylon thread, is in clinical teals in the United States. Early
results are promising, but even if research continues to progress smoothly, it will
be several years before the device could be approved and available (Program for
Applied Research on Fertility Regulation, 1987; Contraceptive Research and
Development Program, 1988~.
Nonsurgical male sterilization techniques have involved the injection of
chemicals, including methylcyanoacrylate, ethanol, and formaldehyde into the
vas deferent. A great deal of additional research is needed to assess He efficacy
and safety of these methods (Harper, 1983~. In China, a sterilization technique in
which a sclerosing chemical is injected into the vas deferens has been performed
on over 1 million men (Segal, 1989~. Another procedure uses the "no-scalpel"
vasectomy technique developed in China, in which a small puncture rather than
an incision is made in the scrotum to locate the vast
METHODS AVAILABLE OUTSIDE THE UNITED STATES
Couples in Western Europe and in some less developed countries have a wider
choice of contraceptive methods and greater access to the latest contraceptive
technology than couples in the United States. In some European countries,
contraceptive implants, new oral contraceptives, injectable contraceptives, and a
variety of IUD s and sterilization devices that are not available in the United States
are approved and marketed. These methods have been found to be safe and
effective means of contraception.
Depo-Provera (depot-medroxyprogesterone acetate or DMPA), taken by
injection every three months, has a failure rate of less than 1 pregnancy per 100
OCR for page 38
38 DEVELOPING NEW CO=~CE~~ES
women per year. It was developed in the United States and is manufactured by
the Upjohn Company in Europe. Depo-Provera has been given limited or general
approval in about 90 countries, including Canada, Sweden, and the United
Kingdom. An estimated 4 million women worldwide use Depo-Provera (Liskin
and Blackburn, 1987~. In 1978, after nearly four years of review, FDA declined to
approve Depo-Provera for use as a contraceptive in the United States (see Chapter
7~.
A two-month injectable, Noriste rat (norethisterone enanthate or NET-EN), is
manufactured by Schering AG in West Germany and is approved in more than 40
countries. Its failure rate is higher than Depo-Provera-about 2 pregnancies per
100 women per year. An estimated 800,000 women worldwide use Noristerat
(Liskin and Blackburn, 1987~. Both Mexico and China manufacture their own
one-month injectables. It is estimated that there are over 300,000 users of
injectables in Mexico and and over 1 million in China (Liskin and Blackburn,
1987~. There are currently eight different injectable contraceptive compounds
being marketed around the world (Kleinman, l9x8~.
NOR PLANT is a progestin-releasing contraceptive implant that is placed
under the skin on the inside of a woman's upper arm. The implant, which is
manufactured in Finland by Leiras Pharmaceuticals, can provide contraceptive
protection for up to five years. The nonbiodegradable capsules containing
levonorgestrel are inserted through a small incision and can be removed by a
trained person when a pregnancy is desired, when their effectiveness declines, or
if the user is troubled by side effects. A six-capsule version of NORPLANT~ has
been tested on more than 55,000 women in 31 countries and has been approved in
at least 12 countries, including Finland in 1983 and Sweden in 1984 (Population
Council, 1988~. In August 1988, a New Drug Application was filled for
NORPLANT~ with the I;DA. In April 1989 the Fertility and Maternal Health
Drug Advisory Committee of the FDA unanimously recommended that
NORPLANT~ be approved for marketing in the United States. Wyeth has
expressed interest in marketing NORPLANT@, if it is approved.
A newer version containing two rods (NORPLANT@-2) and providing con-
craceptive protection for up to three years has been approved in Finland; clinical
trials are under way in nine other countries. Evaluation of NORPLANT@-2 has
been delayed, however, because of problems with the supply of the polymer used
to form Be core of the two rods. Other versions of contraceptive implants using
one rod are also undergoing clinical trials (Wiedhaup, 19889.
The main advantages of NORPLANT~ are its high effectiveness (less than 1
pregnancy per 100 women per year), reversibility, and convenience; in addition,
because NOR PLANT provides among the lowest levels of steroids of any
steroidal method, it has a low incidence of serious adverse health consequences.
Its disadvantages are that it must be inserted and removed by health professionals.
In addition, it typically changes menstrual bleeding patterns, and the capsule's
rods may be visible under the skin.
OCR for page 39
CURRENT STATUS OF CONTRACEPTIVE RESEARCH 39
The Multiload IUD, which is used by a large proportion of all IUD users in
Europe, has never been introduced into the United States. According to the
manufacturer, Organon International, they consider the costs of liability insurance
and of defending possible liability claims in the United States to be too high, and
the negative publicity resulting from such claims to be potentially detrimental to
sales in other countries (Wiedhaup, 1988~. A variety of other IUDs are used in
China and a few other countries, but they are not likely to be introduced to the
American market.
For more than a decade, researchers have tested various chemicals that could
be used to bring on a delayed menstrual period. The most advanced
antiprogesterone, RU486, currently thought to be most effective when used with
prostaglandin analogues, was developed in France by Roussel-Uclaf. During the
past five years, RU486 has been tested in 15 countries, including France, Sweden,
and the United States (scalped, 1987~. It was approved for use in France and
China in 1988. Known generally as mifepristone and marketed in France under
the trade name, Mifegyne, RU486 is an antiprogesterone steroid that blocks the
cells in the uterus from receiving progesterone, which is needed to support the
fertilized egg. (RU486 is discussed further in Chapter 4.)
The Filshie clip, made of titanium lined with silicone rubber, is a method of
occluding the fallopian tubes during female sterilization. It has a low failure rate
and is thought to cause less damage to the tubes, an important consideration
should the woman request a reversal. The Filshie clip has been tested among
more than 10,000 women worldwide and is approved for use in the United
Kingdom and Canada Kristin and Rinehart, 1985~. Oarlock silicone plugs, used
for female sterilization and thought to increase the prospects of reversibility, are
already available in the Netherlands.
CONCLUSION
People in the United States currently have limited options for fertility control
and fewer contraceptive choices than people in several other industrialized countries
and in some developing countries as well. Some improvements in existing
methods will be made in the next decade, and some highly effective new methods
may become available in other countries. Some of these new methods will
probably be safer, easier to use, less expensive, and more acceptable than existing
methods. Other new methods will meet the needs of special population subgroups,
such as lactating women or women over 35.
The prospects for having one or more fundamentally new methods available in
the United States by the year 2000 are negligible. Contraceptive methods that are
fundamentally different from existing technology, such as a contraceptive vaccine,
are likely to have a greater positive impact on the consumer and society as a whole
but will take considerable time to develop.
OCR for page 40
40 DEVELOPING NEW CO=~CE~IVES
Some promising new methods, such as the contraceptive vaccine, for which
much of the basic research has been completed, are not being developed at a rate
that scientific knowledge would allow. Other methods have been approved by
one or more European countries, but additional clinical trials in the United States
are needed to qualify for FDA approval. Moreover, there are continuing
opportunities for basic research in reproductive biology, which may yield significant
contraceptive leads.
Accelerated efforts to develop and introduce new contraceptive products to the
market would lead to a wider variety of contraceptive options for women and men
in the United States and abroad and would result in safer, more effective, and
more acceptable contraception for a much broader population than is being served
by existing methods.
Representative terms from entire chapter:
existing methods
