Parenteral peptide formulations: chemical and physical properties of native luteinizing hormone-releasing hormone (LHRH) and hydrophobic analogues in aqueous solution

The degradation of native LHRH in aqueous buffers of pH approximately 1-10 obeyed the rate equation, kobs = kH + alpha H+ + ko + kHO-(alpha HO-)x, where x at 60-100 degrees C was approximately 0.64 and temperature independent. Extrapolation to 25 degrees C using the Arrhenius equation and secondary rate constants showed that native LHRH is reasonably stable at pH 5.4, giving a shelf life (t90) of approximately 5 years. Regarding physical properties, hydrophobic LHRH analogues nafarelin and detirelix were found to be surface active as demonstrated by a decrease in apparent surface tension with increased peptide concentration. The CMC for detirelix at pH 7.4 was determined to be 5.3 x 10(-4) M (0.88 mg/ml), and that for nafarelin, greater than 2 mg/ml. At higher concentrations (approximately 4-8 mg/ml), nafarelin and detirelix formed nematic liquid crystals of undulose extinction (birefringence, less than 0.001). The thermodynamic stability of these peptide liquid crystals was probed by determining their melting points (Tcm) in the presence of propylene glycol, a solvent which proved to be efficacious at suppressing gelation and at destabilizing liquid crystals as measured by a reduction in Tcm.

Medical treatment of endometriosis: a comparison of the suppressive effects of danazol and nafarelin on reproductive hormones

OBJECTIVE

Patients with endometriosis were studied to investigate hormonal suppression by the gonadotropin-releasing hormone against nafarelin acetate compared with danazol. We hypothesized that the pattern, time course, and degree of gonadotropin and ovarian suppression would be different.

DESIGN

The study included 16 patients who were randomized into one of three 6-month treatment protocols.

SETTING

Patients were recruited from a university hospital setting.

PATIENTS

Eligible candidates were 18 to 45 years of age, with regular menses and documented pelvic endometriosis.

INTERVENTION

Six-month treatment protocols included nafarelin 800 or 400 micrograms/d, or danazol 800 mg/d.

MAIN OUTCOME MEASURES

Serum estradiol (E2), progesterone (P), luteinizing hormone (LH), and follicle-stimulating hormone were determined before treatment and then monthly. Thirteen patients consented to a 12-hour hospital admission during the 5th and 6th month of treatment to determine LH pulse frequency and amplitude.

RESULTS

Estradiol and P were suppressed in all groups, but E2 significantly more by nafarelin than danazol (P less than or equal to 0.01). Nafarelin, 800 micrograms, significantly depressed LH pulse amplitude compared with danazol (P less than or equal to 0.05). Two patients in the nafarelin group had the administration of their medication observed, and both demonstrated single, high-amplitude pulses immediately after administration.

CONCLUSION

Nafarelin is a more potent LH and E2 suppressor than danazol, and the agonist effect of nafarelin may continue to provoke transient gonadotropin responses despite long-term therapeutic suppression.

Pharmacologic management of endometriosis

The incidence, pathogenesis, staging, and treatment of endometriosis are reviewed, with an emphasis on pharmacologic management of this condition. Endometriosis--the presence of ectopic endometrial tissue--can be found in 15-25% of infertile women and may be found in 1-5% of all women between menarche and menopause. Although the pathogenesis of endometriosis is uncertain, the most tenable etiologic theory is a combination of celomic metaplasia and retrograde menstruation. Staging is based on the American Fertility Society classification scheme, with stage I being the mildest and stage IV the most severe form of the disease. The management of endometriosis depends on the extent of the disease, the severity of the symptoms, the age of the patient, and the patient's desire for future fertility. Treatment modalities include expectant management, surgery, induction of a pseudopregnancy state with hormonal therapy (e.g., oral contraceptives), or induction of a pseudomenopausal state. The induction of a pseudomenopausal state with the use of oral danazol gained widespread favor in the 1970s as the treatment of choice in patients with endometriosis, but therapy is often associated with unpleasant adverse effects. Gonadotropin-releasing hormone (GnRH) agonists may provide a safe and clinically effective alternative to danazol therapy in patients with endometriosis. Results of a multicenter study comparing nafarelin with danazol for treatment of endometriosis indicated no significant differences between treatment groups with respect to improvements in disease state and symptomatology. The most common adverse effect associated with nafarelin therapy is hot flashes. The GnRH agonist nafarelin is as effective as danazol or oral contraceptives for the treatment of endometriosis and causes fewer adverse reactions. GnRH agonists may replace danazol as the treatment of choice in patients with endometriosis.

Gonadotropin-releasing hormone agonist-induced ovarian hyperstimulation: low-dose side effects in women and monkeys

OBJECTIVE

To determine whether low (subtherapeutic) doses of gonadotropin-releasing hormone agonists (GnRH-a) can cause ovarian hyperstimulation.

DESIGN

The study is in two parts: a preliminary clinical trial of women and a follow-up study in laboratory primates.

SETTING

Normal human volunteers were studied in an academic research environment; primates were in a conventional laboratory setting.

PATIENTS, PARTICIPANTS

Human volunteers were selected on the basis of apparent normal health. The monkeys were believed to be of normal reproductive status.

INTERVENTIONS

Gonadotropin-releasing hormone agonists were administered at subtherapeutic doses.

MAIN OUTCOME MEASURES

After observing ovarian hyperstimulation in two of five women receiving low doses of GnRH-a, a study was specifically designed to test the hypothesis that at low (subtherapeutic) doses of GnRH-a the "flare-effect" can be sustained without achieving down regulation.

RESULTS

The data in women and monkeys suggest that a highly individualized response to low GnRH-a doses can be manifested as ovarian hyperstimulation.

CONCLUSION

Four points of interpretation are offered: (1) that subtherapeutic doses of GnRH-a can cause ovarian hyperstimulation and related sequelae; (2) this may be a unique observation in that, typically, lower doses of medications have a lower incidence of negative side effects; (3) the findings suggest that GnRH-a prescribed in self-administration regimens may be more prone to such problems in noncompliant patients; and (4) the hyperstimulation response of the ovaries to low GnRH-a doses may indicate a new approach to controlled ovulation induction, although wide individualism was found.

Hormonal therapy before surgical treatment for uterine leiomyomas

Use of GnRH-A offers a promising medical approach to treating uterine leiomyomas. This therapy can be useful in selected patients, preserving fertility by delaying the need for imminent surgical treatment. In selected perimenopausal women, agonist therapy may, in fact, be an alternative to surgical intervention. Shrinking the size of myomas and reducing uterine volume with these agents have been reported to control symptoms of myoma, making myomectomy or vaginal hysterectomy a safer procedure. Used preoperatively, GnRH-A therapy can also reduce the risk of surgical complications and excessive blood loss.

A comparative treatment trial of endometriosis using the gonadotrophin-releasing hormone agonist, nafarelin, and the synthetic steroid, danazol

A randomized and double-blind trial was carried out comparing intranasal nafarelin acetate (400 micrograms daily) and oral danazol (600 mg daily), given over 6 months, in the treatment of 49 patients with laparoscopically proven endometriosis. Both drugs produced a highly significant and similar reduction (of 60 to 70%) in objective American Fertility Society scoring, even in severe disease. No effect was seen on adhesions. Both drugs suppressed oestradiol levels to a similar extent, although nafarelin caused a substantial rise in the first 2 weeks after the initiation of therapy. Nafarelin suppressed LH substantially and FSH, testosterone and prolactin to a small degree, whereas FSH and LH increased slightly during danazol. Pregnancies occurred in 12 of 22 infertile women in the 12 months following nafarelin, and in 6 of 14 in the danazol group. Side-effects were reported at a similar rate with both drugs, but the pattern was different. Hot flushes were the predominant side effect with nafarelin, although oestradiol levels were not suppressed to the extent expected. Small amounts of spotting or light bleeding were experienced with both drugs, but these tended to decrease with time with nafarelin and increase with danazol.

Effect of reversible androgen deprivation on hemoglobin and serum immunoreactive erythropoietin in men

To examine the role of testosterone in the maintenance of hemoglobin levels, we studied the effect of reversible androgen deprivation on hemoglobin, serum immunoreactive erythropoietin, and serum testosterone in seven men treated with a luteinizing hormone-releasing factor (LHRH) agonist for 6 months and then followed for an additional 6 months. The mean serum testosterone level was 4.35 +/- 1.05 ng/ml initially and it decreased to castrate levels in all patients by 6 months. After stopping therapy, there was a rapid increase in serum testosterone such that by 12 months the mean concentration was normal. The pretreatment hemoglobin was 15.2 +/- 0.9 g/dl (mean +/- SD); after 6 months of androgen deprivation it had fallen to 14.1 +/- 0.4 g/dl (P less than 0.05). Six months after stopping therapy, the hemoglobin rose to pre-treatment levels. Before treatment, serum immunoreactive erythropoietin was 9.5 +/- 4.6 mu/ml (mean +/- SD) and did not change significantly during or after the 6 month period of androgen deprivation. No significant inhibition of burst-forming unit-erythroid (BFU-E) or colony-forming unit-granulocyte macrophage (CFU-GM) was observed at the serum level of nafarelin acetate obtainable in vivo. These data suggest that, within the normal range of hemoglobin in men, androgens are a determinant of the red cell mass.

Bone mineral density of the lumbar spine in endometriosis subjects compared to an age-similar control population

The purpose of this study was to compare the lumbar bone mineral density (BMD) between women with endometriosis and age-similar controls. Eighty-five women from nine North American centers (mean age, 30.7 yr) with laparoscopically proven endometriosis (study patients) were enrolled in a study of the efficacy of nafarelin, a GnRH agonist. Fifty-two women (mean age, 32 yr) from the Palo Alto area, with regular menstrual cycles and no major medical problems, served as age-similar controls. Both groups were predominantly (greater than 92%) white. The mean BMD of the lumbar spine was 1.1 g/cm2 in both the study subjects and the controls. Study patients were 104.8% and controls were 104.8% of normal values for age. BMD was not significantly different in the two groups. BMD was not correlated with severity or time from diagnosis of endometriosis. BMD was positively correlated with weight (r = 0.28; P less than 0.05) in both groups, with height (r = 0.30; P less than 0.01) in study patients, and marginally with height (r = 0.26; P less than 0.07) in controls. This study showed no difference in BMD between endometriosis patients and age-similar controls; both groups had normal BMD.

Treatment of endometriosis with the GnRH agonist nafarelin acetate

Additional details of a multicenter study of nafarelin acetate with particular attention to a unique endometriosis scoring system utilized are reviewed. Additional information regarding the relapse of symptoms of 10 patients treated with nafarelin and danazol during a 6- to 12-month follow-up interval is described. Transient decreases in leukocytes previously reported by other investigators were observed in 3 of 8 patients, but appear to represent a laboratory artifact.

Evidence of similar increases in bone turnover during nafarelin and danazol use in women with endometriosis

Medical 'oophorectomy' by GnRH agonist or danazol is an effective treatment for endometriosis. Since increased bone loss is a potential risk of hypoestrogenism, we compared the effect of nafarelin and danazol treatment on bone metabolism. Twelve patients with laparoscopically confirmed endometriosis received nafarelin (400 micrograms day intranasally) and six patients danazol (600 mg day orally) for 6 months. Both treatments had already led to hypoestrogenism (E2 less than 21.6 pg/ml) after 3 months. They both were accompanied by an approximately 50% rise in 24-h urinary hydroxyproline output, suggesting accelerated bone resorption at 6 months; yet urinary calcium output did not change significantly. Serum osteocalcin rose by 80-120% and bone alkaline phosphatase activity by 34-40%, suggesting stimulated bone formation at the same time. No detectable changes ensued in cortical bone mineral content in the distal radius or in serum levels of calcium, calcitonin, parathyroid hormone, or aminoterminal propeptide of type III collagen. Three months after treatment, hydroxyproline output, serum osteocalcin and bone alkaline phosphatase were still elevated in women taking nafarelin, whereas only serum osteocalcin was elevated in women taking danazol. Our data thus suggest that bone turnover was increased during nafarelin and danazol therapy and that this effect was reversible.

Nafarelin acetate: a gonadotropin-releasing hormone agonist for the treatment of endometriosis

Nafarelin acetate is a gonadotropin-releasing hormone (GnRH) agonist proven as effective as danazol in treating endometriosis. Its proposed mechanism of action is the desensitization of pituitary GnRH receptors leading to a decrease in gonadotropin release, and ovarian hormone serum concentrations similar to those achieved in postmenopausal women. Nafarelin decreases or ablates the physical symptoms associated with endometriosis, and pregnancy rates following therapy with this drug are comparable to rates observed after danazol therapy. Nafarelin is administered by nasal inhalation and has been generally well tolerated. It is associated with a high incidence of adverse effects but they are rarely severe enough to cause withdrawal from treatment, and those occurring most frequently--hot flashes, vaginal dryness, and decreased libido--are a consequence of the hypoestrogenemia induced by the drug. Increased bone turnover occurs in women on nafarelin but biochemical parameters return to pretreatment concentrations by six months after termination of treatment. This agent's place in the therapy of endometriosis will be determined as clinical experience accumulates.

Medical treatment of mild endometriosis in infertile women: analysis of a failure

The easy access to the pelvis of infertile women by laparoscopy favours early diagnosis of endometriosis in an increasing number of subjects with minimal and mild disease. These initial forms have been associated with and considered as the cause of infertility despite the absence of relevant scientific evidence. Various hormone therapies, some with severe side-effects and high costs, have been used by numerous authors. However, no study comparing medically treated with untreated women has ever shown any drug to be more effective than expectant management. The possible explanations of treatment failures are reviewed.

Preserving adult height potential in girls with idiopathic true precocious puberty

We designed a prospective study of height potential in girls with idiopathic precocious puberty, comparing the presenting features of girls with and without evidence of reduced adult height potential. The 14 girls with impaired adult height prognoses (group 1) were reexamined after treatment with a gonadotropin releasing hormone agonist, nafarelin. The seven girls with the prognosis of unimpaired height (group 2) were followed without therapy. We found that the group could be distinguished at initial examination by the greater bone age/height age ratio of group 1 (mean +/- SEM: 1.4 +/- 0.06 vs 1.0 +/- 0.05; p less than 0.005) and by the greater difference between predicted height and target height in group 1. The mean predicted height in group 1 was significantly less than the mean target height (150.7 +/- 2.1 vs 165.4 +/- 3.0 cm; p less than 0.005), whereas the mean predicted and target heights in group 2 were similar (165.4 +/- 3.0 vs 164.3 +/- 2.1 cm). Initial estradiol levels were also greater in group 1 than in group 2 (21.6 vs 10.6 pg/ml; p less than 0.05), although this difference was not sustained during follow-up. In group 1, nafarelin therapy suppressed the pituitary-gonadal axis, and although there was a transient reduction in height potential in girls with the youngest bone ages during the first 6 months of therapy, 2 years of treatment slightly improved predicted heights from 150.7 +/- 2.1 to 152.7 +/- 2.0 cm (p less than 0.05). Height predictions also increased without therapy during the 2-year observation period in group 2, from 165.4 +/- 3.0 to 168.7 +/- 4.1 cm (p less than 0.05). Our data indicate that gonadotropin releasing hormone agonist therapy preserves height potential in girls with an initially impaired height prognosis, and that height potential is preserved without therapy in those with a good initial height prognosis.

The effects of nafarelin and danazol on vertebral trabecular bone mass in patients with endometriosis

Single and dual-energy quantitative computed tomography (QCT) were used to measure spinal trabecular bone mineral content in 24 women treated with either nafarelin (15 patients) or danazol (nine patients) for endometriosis. Significant loss of bone mineral (-9.6 g/l; -5.9% P less than 0.001) was demonstrated after 6 months' treatment with nafarelin. This loss was reversible with no significant difference in the bone mineral measurement made before treatment and that made at 6 months after treatment was stopped (difference -1.95 g/l, NS). A small but statistically significant (+2.2 g/l, P less than 0.05) increase in bone mineral was measured in the group of patients treated with danazol for 6 months. The dual-energy QCT gave similar results, indicating little change in trabecular fat content. A significant correlation was demonstrated between mean serum oestradiol levels during treatment with nafarelin and the change in bone mineral (r = 0.655, P less than 0.005).

Nafarelin controlled release injectable: theoretical clinical plasma profiles from multiple dosing and from mixtures of microspheres containing 2 per cent, 4 per cent and 7 per cent nafarelin

Nafarelin controlled release injectable (CRI) releases a decapeptide drug for target one month therapy. Nafarelin, a luteinizing hormone releasing hormone agonistic analogue, is microencapsulated in biodegradable poly(lactide-co-glycolide) microspheres and given by intramuscular injection. Clinical data from a human single dose Phase I clinical study are modelled to develop theoretical multiple dose profiles and theoretical single dose profiles from mixtures of two or three formulations. Single dose injections of nafarelin CRI microspheres (4 mg nafarelin) containing 2, 4, or 7 per cent nafarelin all achieve useful plasma drug levels throughout the target 30 day interval. Therapeutic suppression of testosterone levels was observed in all subjects participating in the phase I clinical study. Highest plasma nafarelin levels are achieved in the 0-10 and 20-35 day post-injection intervals. Theoretical multiple dosing profiles generated from the single dose clinical results show significant oscillations in plasma nafarelin levels depending on the particular dosing interval selected. Thirty or forty day dosing intervals yield significant variability in plasma nafarelin levels at steady state; 15 day dosing intervals show less variability. Therapeutic testosterone suppression was observed in the single dose study, so the nafarelin dose per injection can be reduced in multiple dosing therapies. Theoretical plasma nafarelin profiles from certain mixtures of 2 and 4 per cent nafarelin microspheres or 2 and 7 per cent nafarelin microspheres indicate that a 60 day product could be achieved. In general, all three formulations yield their lowest plasma drug levels during the 10-20 day post-injection interval. Therefore any mixture of these formulations will likewise exhibit low plasma drug levels during this interval.

Changes in vitamin D metabolism during natural and medical menopause

Thirty-nine women were studied longitudinally for 3 yr, during which period 10 women passed a natural menopause. Vitamin D metabolites were determined every 3 months in these 10 women. The same variables were studied in 42 premenopausal women with endometriosis treated for 6 months with nafarelin acetate (a LHRH agonist) given alone in a dose of 200 or 400 micrograms or in a dose of 400 micrograms combined with 1.2 mg norethisterone (NET)/day and followed-up for a further 6 months. No changes were seen in 1,25-dihydroxyvitamin D [1,25-(OH)2D], vitamin D-binding protein, or the free index of 1,25-(OH)2D during the natural menopause. A small increase was found in 25-hydroxyvitamin D [25OHD] and 24,25-(OH)2D3 after correction for seasonal variation. All three nafarelin groups had a significantly decreased free index of 1,25-(OH)2D, which returned to the baseline value on withdrawal of the treatment. Serum 25OHD and 24,25-(OH)2D3 were increased at 6 months and thereafter decreased to baseline values. These changes were still visible after correction for seasonal variation. Vitamin D-binding protein showed a small transient increase in the nafarelin plus NET group, but was unchanged in the other two groups. The 24-h urinary excretion of calcium increased significantly in the groups receiving nafarelin alone, whereas it remained unchanged in the nafarelin plus NET group. We conclude that detectable changes in 1,25-(OH)2D do not occur in natural menopause. Treatment with LHRH agonists produces a significant decrease in serum 1,25-(OH)2D, which does not seem to be dependent on increased bone resorption. This suggests that LHRH agonists may induce a change in other pituitary hormones involved in vitamin D regulation.

A comparison of nafarelin acetate and danazol in the treatment of endometriosis

Nafarelin 400 micrograms daily and danazol 600 mg daily were compared in a double-blind randomized study. Eighty-two patients with endometriosis were treated for 6 months after an initial laparoscopy and 74 had a second laparoscopy. Twenty-two (30%) patients had complete disease regression, 42 (57%) patients had a partial regression, and in 10 (13%) patients disease was unchanged or worse. Both treatments led to significant regression of active disease but not of adhesions. At 3 months follow-up, 34 (64%) patients reported their symptoms were improved, 15 (28%) reported no change, and 4 (8%) were worse. Nafarelin was associated with more hot flushes and headaches, and danazol with more weight gain. No significant differences, however, were noted in treatment efficacy between the two groups.

The ratios of serum bioactive/immunoreactive luteinizing hormone and follicle-stimulating hormone in various clinical conditions with increased and decreased gonadotropin secretion: reevaluation by a highly sensitive immunometric assay

Serum bioactive and immunoreactive LH and FSH were measured in clinical conditions with increased or decreased gonadotropin secretion. Gonadotropin immunoreactivity was measured using a conventional RIA (I) and an ultrasensitive immunofluorometric method (F). Bioactive (B) LH was assessed by the mouse interstitial cells in vitro bioassay, and B-FSH using the immature rat granulosa cell assay. Acute GnRH stimulation of adult men (n = 6) increased LH levels measured by the different methods 4.3- to 5.3-fold. The B/I ratio of LH increased from 2.34 +/- 0.21 to 3.71 +/- 0.36 (mean +/- SEM) at 120 min (P less than 0.05), but no change was found in the B/F ratio. After ovariectomy of premenopausal women (n = 6), the LH levels increased in 1 week 4- to 6-fold, the B/I ratio from 1.85 +/- 0.22 to 2.59 +/- 0.24, and the B/F ratio from 1.78 +/- 0.22 to 2.90 +/- 0.30 (P less than 0.05 for both). In addition, the LH levels were measured during GnRH agonist treatment of ovarian carcinoma (n = 8), endometriosis (n = 8), and prostatic carcinoma after orchiectomy (n = 8). In the two former groups, serum B-LH decreased in 1 month to undetectable levels (less than 0.5 IU/L), and in the prostate cancer patients to 1.2 (0.8-1.9) IU/L (log mean and range of +/- SEM). The concomitant decline of I-LH was to 1.5-1.9 IU/L in the agonist-treated female patients, and that of F-LH to 0.10-0.15 IU/L; in the prostate cancer patients, respectively, these values were 7-8 and 0.3-0.7 IU/L. The B/I and B/F ratios during the agonist treatments could only be calculated in the prostate cancer patients (in the others, B-LH became undetectable). The B/I ratio decreased from 2.34 +/- 0.5 to 0.14 +/- 0.03 (P less than 0.01), but no suppression was found in the B/F ratio from a pretreatment value of 3.6 +/- 0.8. B-, I-, and F-FSH levels were measured in the GnRH agonist-treated orchiectomized prostate cancer patients. The pretreatment level of B-FSH was 154 (137-175), that of I-FSH was 38.0 (34.4-42.0), and that of F-FSH was 39.8 (35.3-44.9) IU/L. The B/I ratio of FSH was 3.76 +/- 0.49, and the B/F ratio was 3.53 +/- 0.59. The mean B-FSH level decreased during treatment by 87-93.5%, that of I-FSH by 98%, and that of F-FSH by 91.5% (P less than 0.01 for all).(ABSTRACT TRUNCATED AT 400 WORDS)

Antiendometrial antibodies in endometriosis measured by an enzyme-linked immunosorbent assay before and after treatment with danazol and nafarelin

No previous study has investigated prospectively the quantitative effect of treatment on antiendometrial antibody levels in endometriosis. We measured antiendometrial antibody levels by an enzyme-linked immunosorbent assay in 35 women with laparoscopically proved endometriosis who were treated for 6 months with danazol (N = 11) or nafarelin (N = 24) in a randomized double-blind study. Levels before treatment were significantly higher than in a control group (P less than .001). Levels were lowered by treatment, but to a significant extent only in the nafarelin group (P less than .001) (danazol group: P = .091). Our data suggest that in relation to antiendometrial antibodies, nafarelin has a suppressive effect which has previously been ascribed only to danazol.