**6. Clinical evaluation in healthy women and women with endometriosis**

RU-486 was originally developed for emergency contraception, however early observations with lower doses than those used clinically, indicated that when given acutely during the luteal phase, RU-486 would facilitate the onset of menstruation by the upregulation of endometrial prostaglandins and given chronically, RU-486 would delay menses (Hapangama et al., 2002; Shoupe et al., 1987). The effects of RU-486 on the ovarian cycle and endometrium appear to be dose dependent, that is low doses interfere with estrogen function and disrupt endometrial growth (Croxatto et al., 1993; Narvekar et al., 2004), but higher doses additionally suppress follicular development by impairing gonadotrophin secretion (Gemzell-Danielsson et al., 1996; Liu et al., 1987; Spitz et al., 1993; 1994). These observations strike a resounding chord with those data acceded in the macaque described earlier. The potential value of PRAs as alternative contraceptives to current combined or progestin-only pills have been long recognised and evaluated in a number of different dosing and delivery strategies (Baird et al., 2003; Brown et al., 2002; Chabbert-Buffet et al., 2007; Heikinheimo et al., 2007; Lakha et al., 2007; Nayak et al., 2007). Whilst no pregnancies were reported after 200 months in women who received 2-5 mg RU-486 daily (Brown et al., 2002), lower doses appeared to be less effective (Croxatto et al., 1998). Similar observations on the suppression of ovulation and the normal menstrual cycle have also been made with

Progesterone Resistance and Targeting

observations of GnRH receptor agonists (Grow et al., 1996).

data are anticipated on its clinical efficacy/safety profile.

endometrial growth (Figure 3).

steroidal PRA class.

the Progesterone Receptors: A Therapeutic Approach to Endometriosis 171

improvements in dyspareunia symptoms and fertility outcomes. Whilst no visualisation of the change in the disease burden was made in this study, this assessment was followed up by others (Cornillie et al., 1986) and incorporated as part of the validation work performed by Kettel and co-workers with RU-486. In these studies, doses of RU-486 were carefully selected to avoid the known anti-glucocorticoid effects. Treatment of women with endometriosis with a daily dose of 5-100 mg for 3-6 months resulted in durable inhibition of the normal menstrual cycle (although not optimal for the 5 mg dose) and a suppression in ovarian hormone levels consistent with a block on folliculogenesis. Endometriosis-associated pain scores and American Fertility Scores determined by laparoscopic examination also decreased from baseline (Kettel et al., 1994; 1996; 1998; Murphy et al., 1995). These preliminary studies were not able to rule out the possibility that the visible changes in disease burden were secondary to the absence of ovarian hormone cyclicity; indeed this is still not known. From a safety perspective, there was no suppression of cortisol levels, indicative of anti-glucocorticoid effects. Serum estradiol concentrations were also maintained at a mid-follicular level which preserved femur and lumbar spinal bone mineral density (Kettel et al., 1996). These bone safety data are consistent with those reported in the cynomolgus macaque and contrast clinical

Asoprisnil has also been compared with placebo for treatment of pain in laparoscopically diagnosed endometriosis in a randomized, controlled trial. Whilst the results of this study were reported as an abstract only, a significant decrease in daily pain scores with all doses of asoprisnil (5, 10 or 25 mg) compared with placebo was noted (Chwalisz et al., 2005b). Intriguing as these data are, there has been a compelling lack of replication studies from double blinded, randomised and controlled trials in women with endometriosis, using empirical and objective outcome measures approved by regulatory bodies. This lack of evidence may be in part due to the level of investment needed for such an old drug as RU-486, or concerns over the safety of continuously administered RU-486 or PRAs like it. CDB-4124 is currently in development for the treatment of endometriosis and uterine fibroids and

In contrast to the relatively large wealth or reported data with steroidal PRAs, there is only a single study evaluating the effects of a non-steroidal PRA, PF-02413873, in healthy female subjects (Howe et al., 2011). When orally dosed to healthy female volunteers, daily from the first day of the menstrual cycle, PF-02413873 blocked the mid-cycle LH surge and

Whilst PF-02413873 development for endometriosis was curtailed due to a high incidence of idiosyncratic maculopapular rash, PF-02413873 proves the principle that a non-steroidal PRA can similarly block the effects of follicular hormones on endometrial growth as steroidal PRAs. Further data are needed to determine whether the histological changes encountered by the class of steroidal PRAs endometrial are similarly manifested by the non-

Given the anti-proliferative effects observed in vitro and in vivo for PRAs (Freeburg et al., 2009b; Goyeneche et al., 2007; Ohara et al., 2007; Poole et al., 2006; Tieszen et al., 2011), the broader utility of this class in treating other benign and malignant growth conditions has not gone unnoticed (Chwalisz et al., 2007; Robertson et al., 1999; Rocereto et al., 2000; Wilkens et al., 2008). In the closely related condition of uterine fibroids, small studies have

other PR-As such as a onapristone, J-876 as well as CDB-2914 (Chabbert-Buffet et al., 2007; Chwalisz et al., 2005a; Katkam et al., 1995; Stratton et al., 2000). The utility of PRAs as a new class of oral contraceptives has still not been fully exploited and this feature alone is anticipated to have potential benefit in endometriosis patients by reducing cyclical menstrual pain.

Intrauterine delivery (IUD) of progestogens (levonorgestrel/Mirena) is an effective way of administering durable contraceptive exposures of drug and to bypass systemic side effects. IUD studies with PRAs in the macaque have also been followed up with a single human study. The study compared levonorgestrel with an IUD releasing ZK-230211. The dose of ZK-230211 was selected based on an equivalent IUD dose of ZK-230211 that suppressed ovulation and menstruation in the macaque (Heikinheimo et al., 2007). In contrast to the data acceded in the macaque, however, the ZK-230211 IUD did not appreciably alter bleeding patterns suggesting that either the local drug exposure was insufficient or that there are translational differences between the macaque and human.

Increasingly, however, the endometrial effects of PRAs have been subject to concern due observed histological changes in the endometrium with chronic exposure. In the past, endometrial hyperplasia has been reported as a safety concern with chronic use of RU-486 (Newfield et al., 2001). Recent, detailed histological analyses of endometrial biopsies from patients exposed to steroidal PRA for more than 3 months have indicated that these agents produce a slightly thickened endometrium with cystically dilated endometrial glands (Ioffe et al., 2009; Mutter et al., 2008; Williams et al., 2007). The appearance of glandular epithelium appears to change with dose and exposure duration, from inactive/non-mitotic to non-physiologic combinations of features usually seen separately in normal proliferative and secretory endometrium. These alterations do not appear to be limited to the glands only, as thick-walled vessels most commonly seen in endometrial polyps, become more widely distributed throughout the endometrium. Whether these effects on the endometrium are mediated by the unopposed effects of persistent follicular phase levels of estradiol, the pharmacological class or some non-specific effect of PRAs on the endometrium is not clear, but this appears to be a common feature of all steroidal PRAs assessed so far. Individuals on prolonged exposure to asoprisnil/J-867 were at a higher risk of developing endometrial changes sufficient to raise concern with regulatory authorities indicates that more research is needed to understand the phenomenon of PRA associated endometrial changes and whether this might be in part mitigated by an alternative dosing regimen from continuous dosing (Baird et al., 2003).

The first evidence that PRAs such as RU-486 would have a potential benefit in women with endometriosis was published by Kettel and co-workers (1991; 1994; 1996; 1998). The incentive for these early investigational studies was the clinical observation that RU-486 could block follicular maturation and ovulation when given early in the menstrual cycle, disrupt endometrial integrity when administered in the luteal phase and induce an anovulatory amenorrhoea when administered continuously. However, even earlier studies than those conducted with RU-486, indicated the potential utility of treating women with endometriosis with an anti-progestin (Coutinho, 1982). In this small openlabel study, 20 patients with endometriosis were subjected to 6 months of continuous treatment with gestrinone (5 mg/twice weekly), a reportedly mixed antagonist with antiprogestogenic activity. All subjects became amenorrhoeic and had reportedly dramatic

other PR-As such as a onapristone, J-876 as well as CDB-2914 (Chabbert-Buffet et al., 2007; Chwalisz et al., 2005a; Katkam et al., 1995; Stratton et al., 2000). The utility of PRAs as a new class of oral contraceptives has still not been fully exploited and this feature alone is anticipated to have potential benefit in endometriosis patients by reducing cyclical

Intrauterine delivery (IUD) of progestogens (levonorgestrel/Mirena) is an effective way of administering durable contraceptive exposures of drug and to bypass systemic side effects. IUD studies with PRAs in the macaque have also been followed up with a single human study. The study compared levonorgestrel with an IUD releasing ZK-230211. The dose of ZK-230211 was selected based on an equivalent IUD dose of ZK-230211 that suppressed ovulation and menstruation in the macaque (Heikinheimo et al., 2007). In contrast to the data acceded in the macaque, however, the ZK-230211 IUD did not appreciably alter bleeding patterns suggesting that either the local drug exposure was insufficient or that

Increasingly, however, the endometrial effects of PRAs have been subject to concern due observed histological changes in the endometrium with chronic exposure. In the past, endometrial hyperplasia has been reported as a safety concern with chronic use of RU-486 (Newfield et al., 2001). Recent, detailed histological analyses of endometrial biopsies from patients exposed to steroidal PRA for more than 3 months have indicated that these agents produce a slightly thickened endometrium with cystically dilated endometrial glands (Ioffe et al., 2009; Mutter et al., 2008; Williams et al., 2007). The appearance of glandular epithelium appears to change with dose and exposure duration, from inactive/non-mitotic to non-physiologic combinations of features usually seen separately in normal proliferative and secretory endometrium. These alterations do not appear to be limited to the glands only, as thick-walled vessels most commonly seen in endometrial polyps, become more widely distributed throughout the endometrium. Whether these effects on the endometrium are mediated by the unopposed effects of persistent follicular phase levels of estradiol, the pharmacological class or some non-specific effect of PRAs on the endometrium is not clear, but this appears to be a common feature of all steroidal PRAs assessed so far. Individuals on prolonged exposure to asoprisnil/J-867 were at a higher risk of developing endometrial changes sufficient to raise concern with regulatory authorities indicates that more research is needed to understand the phenomenon of PRA associated endometrial changes and whether this might be in part mitigated by an alternative dosing regimen from continuous

The first evidence that PRAs such as RU-486 would have a potential benefit in women with endometriosis was published by Kettel and co-workers (1991; 1994; 1996; 1998). The incentive for these early investigational studies was the clinical observation that RU-486 could block follicular maturation and ovulation when given early in the menstrual cycle, disrupt endometrial integrity when administered in the luteal phase and induce an anovulatory amenorrhoea when administered continuously. However, even earlier studies than those conducted with RU-486, indicated the potential utility of treating women with endometriosis with an anti-progestin (Coutinho, 1982). In this small openlabel study, 20 patients with endometriosis were subjected to 6 months of continuous treatment with gestrinone (5 mg/twice weekly), a reportedly mixed antagonist with antiprogestogenic activity. All subjects became amenorrhoeic and had reportedly dramatic

there are translational differences between the macaque and human.

menstrual pain.

dosing (Baird et al., 2003).

improvements in dyspareunia symptoms and fertility outcomes. Whilst no visualisation of the change in the disease burden was made in this study, this assessment was followed up by others (Cornillie et al., 1986) and incorporated as part of the validation work performed by Kettel and co-workers with RU-486. In these studies, doses of RU-486 were carefully selected to avoid the known anti-glucocorticoid effects. Treatment of women with endometriosis with a daily dose of 5-100 mg for 3-6 months resulted in durable inhibition of the normal menstrual cycle (although not optimal for the 5 mg dose) and a suppression in ovarian hormone levels consistent with a block on folliculogenesis. Endometriosis-associated pain scores and American Fertility Scores determined by laparoscopic examination also decreased from baseline (Kettel et al., 1994; 1996; 1998; Murphy et al., 1995). These preliminary studies were not able to rule out the possibility that the visible changes in disease burden were secondary to the absence of ovarian hormone cyclicity; indeed this is still not known. From a safety perspective, there was no suppression of cortisol levels, indicative of anti-glucocorticoid effects. Serum estradiol concentrations were also maintained at a mid-follicular level which preserved femur and lumbar spinal bone mineral density (Kettel et al., 1996). These bone safety data are consistent with those reported in the cynomolgus macaque and contrast clinical observations of GnRH receptor agonists (Grow et al., 1996).

Asoprisnil has also been compared with placebo for treatment of pain in laparoscopically diagnosed endometriosis in a randomized, controlled trial. Whilst the results of this study were reported as an abstract only, a significant decrease in daily pain scores with all doses of asoprisnil (5, 10 or 25 mg) compared with placebo was noted (Chwalisz et al., 2005b). Intriguing as these data are, there has been a compelling lack of replication studies from double blinded, randomised and controlled trials in women with endometriosis, using empirical and objective outcome measures approved by regulatory bodies. This lack of evidence may be in part due to the level of investment needed for such an old drug as RU-486, or concerns over the safety of continuously administered RU-486 or PRAs like it. CDB-4124 is currently in development for the treatment of endometriosis and uterine fibroids and data are anticipated on its clinical efficacy/safety profile.

In contrast to the relatively large wealth or reported data with steroidal PRAs, there is only a single study evaluating the effects of a non-steroidal PRA, PF-02413873, in healthy female subjects (Howe et al., 2011). When orally dosed to healthy female volunteers, daily from the first day of the menstrual cycle, PF-02413873 blocked the mid-cycle LH surge and endometrial growth (Figure 3).

Whilst PF-02413873 development for endometriosis was curtailed due to a high incidence of idiosyncratic maculopapular rash, PF-02413873 proves the principle that a non-steroidal PRA can similarly block the effects of follicular hormones on endometrial growth as steroidal PRAs. Further data are needed to determine whether the histological changes encountered by the class of steroidal PRAs endometrial are similarly manifested by the nonsteroidal PRA class.

Given the anti-proliferative effects observed in vitro and in vivo for PRAs (Freeburg et al., 2009b; Goyeneche et al., 2007; Ohara et al., 2007; Poole et al., 2006; Tieszen et al., 2011), the broader utility of this class in treating other benign and malignant growth conditions has not gone unnoticed (Chwalisz et al., 2007; Robertson et al., 1999; Rocereto et al., 2000; Wilkens et al., 2008). In the closely related condition of uterine fibroids, small studies have

Progesterone Resistance and Targeting

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60(1):63-68.

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demonstrated a reduction in myoma volume and uterine bleeding with asoprisnil and RU-486 (Chabbert-Buffet et al., 2005; DeManno et al., 2003; Fiscella et al., 2006). Larger studies have been completed for asoprisnil. In one randomized, controlled trial, 129 women with at least 1 fibroid greater than 3 cm in diameter or a uterine volume twice the normal (>200 cm3) were treated for up to 3 months with asoprisnil (5, 10, or 25 mg) or placebo (Chwalisz et al., 2007). Significant reduction in uterine fibroid volume was noted by week 4 and persisted through the end of the study in a dose-dependent fashion.

Fig. 3. Effect of escalating multiple dose of PF-02413873 on endometrial thickness (mm) (a) and the mid cycle LH surge (mIU/mL) (b) in healthy women compared with placebo (Howe et al., 2011)
