Cilostazol and Its Effects on Resumption of Meiosis in the Human Ovary
Condition: Contraception
Study type: Interventional
Phase: Phase 2

Summary: 
      Combined oral contraceptive pills (COCs) are the most commonly used hormonal form of birth
      control in the United States with at least 87% of women of reproductive age reporting oral
      contraceptive use at some point in their lives (9). Despite their frequent use, the six and
      twelve month discontinuation rates for oral contraceptive pills are 31 and 47 % respectively
      (17), with common reasons for discontinuation attributed to the side effects of abnormal
      bleeding, headache, and weight gain.

      Additionally, COCs are contraindicated in certain groups of women as outlined by The Centers
      for Disease Control Medical Eligibility Criteria (11). Given the high prevalence of oral
      contraceptive users who commonly discontinue use secondary to side effects or who are not
      eligible for use as a result of underlying health conditions, the development of novel oral
      non-hormonal methods that are equally effective at pregnancy prevention are warranted.

      This current study aims to evaluate the effect of an FDA approved drug, Cilostazol, on human
      oocyte maturation. Such a study has not been conducted to date. If Cilostazol demonstrates an
      ability in humans to affect resumption of meiosis, then this non-hormonal agent could be uses
      as a possible contraceptive agent in the future. This knowledge would have profound
      reproductive health implications.

      The investigators propose that women undergoing treatment with the FDA approved dose of 100mg
      PO every 12 hours of Cilostazol will demonstrate an impairment of egg maturation in
      comparison to paired historic controls following ovarian follicle stimulation.
    

Detailed description: 
      Combined oral contraceptive pills (COCs) are the most commonly used hormonal form of birth
      control in the United States with at least 87% of women of reproductive age reporting oral
      contraceptive use at some point in their lives (9). Despite their frequent use, the six and
      twelve month discontinuation rates for oral contraceptive pills are 31 and 47 % respectively
      (17), with common reasons for discontinuation attributed to the side effects of abnormal
      bleeding, headache, and weight gain.

      Additionally, COCs are contraindicated in certain groups of women as outlined by The Centers
      for Disease Control Medical Eligibility Criteria (11). Given the high prevalence of oral
      contraceptive users who commonly discontinue use secondary to side effects or who are not
      eligible for use as a result of underlying health conditions, the development of novel oral
      non-hormonal methods that are equally effective at pregnancy prevention are warranted.

      The potential for the development of non-hormonal contraception has been present in the
      scientific literature since the 1980s at which point the critical components of gametogenesis
      of the mammalian oocyte were being classified. Bornslaeger and colleagues discovered that
      high concentrations of intracellular cAMP, an important second messenger for many biological
      processes, inhibited resumption of meiosis I in mouse oocytes (3). Later studies demonstrated
      that phosphodiesterase 3 inhibitors, capable of preventing the breakdown of cAMP, were able
      to prevent resumption of meiosis in mouse oocytes cultured in vitro (6).

      Since the 1980s, additional studies have examined phosphodiesterase inhibitors and their role
      in prevention of oocyte maturation. Tsafriri and colleagues showed that phosphodiesterase
      inhibitors were able to exert their effects selectively via type specific isoforms. This
      study revealed that granulosa cells exert effects via type 4 phosphodiesterase inhibitors and
      oocytes respond to signals via type 3 phosphodiesterase inhibitors such that oocyte
      maturation was prevented in the presence of PDE3 inhibitors yet ovulation was unaffected
      (15). Most recently, Jensen and colleagues examined both in vitro and in vivo effects of a
      phosphodiesterase 3 inhibitor ORG 9935 on oocyte maturation in rhesus monkeys. In these
      animal studies, it was found that in vitro, ORG 9935 at a concentration of 1.0umol/l was able
      to completely inhibit oocyte maturation (7).

      In vivo models demonstrated a similar reduction in oocyte maturation, with the most dramatic
      reduction in monkeys treated with an extended dose regimen of ORG 9935 (200mg/kg/d) prior to
      ovulation (8). Additionally, pregnancy rates in macaques treated with ORG 9935 was studied
      and compared to controls. Overall, there was not a statistically significant decrease in
      pregnancy rates in those macaques treated with PDE3 inhibitor; however, there did appear to
      be evidence of a dose response as no animal became pregnant who had serum ORG 9935 levels
      above 300nM/L (9). Despite a clear dose response, authors of this study acknowledge that
      PDE3-Is have systemic effects that are also dose-limiting. At higher doses, adverse effects
      such as tachycardia and hypotension were observed.

      Phosphodiesterase 3 inhibitors have additionally been studied in vitro to assess oocyte
      maturation in humans. Human oocytes cultured in the presence of ORG 9935 (1um) for 24 hours
      demonstrated a statistically significant reduction in germinal vesicle breakdown (an early
      marker of oocyte maturation) in comparison to control oocytes (12). However, no human in vivo
      models assessing oocyte maturation following treatment with a phosphodiesterase 3 inhibitor
      exist.

      Cilostazol, an FDA approved drug for the treatment of intermittent claudication, is a class
      IIIa phosphodiesterase inhibitor. Its systemic effects in humans include vasodilation,
      decrease in platelet aggregation, reduction in triglyceride levels, and increase in HDL
      cholesterol levels (4). Human clinical trials did not address fertility and pregnancy rates;
      however, manufacturer product labeling reports that no fertility effects occurred in rats.
      Most recently, however, two animal in vivo studies examining pregnancy rates of mice treated
      with Cilostazol were conducted (1,10). In both of these studies, mice treated with Cilostazol
      were shown to be completely infertile at follow up; however, once the drug was discontinued,
      all mice that were unable to conceive during treatment with cilostazol were subsequently able
      to have pregnancies of normal litter sizes. It is important to mention that in the study by
      Albarzanchi, mice received PO cilostazol at a dose of 7.5 or 15 mg PO for three days (1). In
      the study by Li conducted in China, the maxium dose was higher (300mg/kg) (10). Pregnancy
      outcomes for both studies were the same.

      These studies demonstrate two important aspects of a contraceptive method: efficacy and
      reversibility. Additionally, the investigators who published Cilostazol's fertility effects
      in mice published an abstract demonstrating a similar effect in swine (2). When a human dose
      of 100mg bid of Cilostazol was given prior to ovulation, no documented pregnancies occurred.
      Following cessation of study drug, all swine were able to conceive.

      Given the success of phosphodiesterase inhibitors in both in vivo and in vitro models for
      prevention of oocyte maturation and pregnancy in animal models, it is reasonable that we
      further examine this potential non-hormonal oral contraceptive method. Given the many FDA
      clinical trials that need to be conducted, new contraceptive methods take decades to develop.
      However, since Cilostazol is an approved FDA medication with an acceptable side effect
      profile, we believe that it is appropriate to complete initial studies of this drug in humans
      using an in vivo technique validated in macaques, a model with the same timing of
      peri-ovulatory events as women, to ascertain its possible use as a non-hormonal oral
      contraceptive.

      The primary objective of the research study is to determine if women taking Cilostazol
      demonstrate impairment of oocyte maturation in comparison to paired historic controls
      following ovarian follicle stimulation. For the purposes of our study, oocyte maturation will
      be assessed using the oocyte maturational stages of prophase I, metaphase I, and metaphase
      II. Thus, we will be assessing the percent of oocytes aspirated from follicles during
      controlled ovarian stimulation that progress beyond the germinal vesicle stage (e.g. GVBD) in
      those women receiving cilostazol and compare this to the maturation of oocytes obtained from
      the same women who underwent ovarian follicle stimulation previously while not on study drug.

      We propose that women undergoing treatment with the FDA approved dose of 100mg PO BID of
      Cilostazol will demonstrate an impairment of oocyte maturation in comparison to paired
      historic controls following ovarian follicle stimulation.
    

Intervention name(s): Cilostazol
Intervention type(s): Drug
Other intervention name(s): Pletal
Intervention MeSH terms: Cilostazol
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: contraception; Cilostazol; phosphodiesterase inhibitors; To assess the ability of Cilostazol to act as a contraceptive agent