Absorption, Distribution and Excretion
Leuprorelin is typically administered as a single-dose, long-acting formulation using microspheres or biodegradable solid sustained-release technology. Regardless of the specific formulation and initial dose strength, peak plasma concentration (Cmax) is usually reached 4–5 hours after injection, with significant individual variability, ranging from 4.6 to 212 ng/mL. Final steady-state plasma concentrations are typically reached within four weeks, with a narrow range of 0.1–2 ng/mL. The effect of food on absorption has not yet been studied. In three patients, less than 5% of the initial dose was recovered in urine after administration of 3.75 mg of leuprorelin sustained-release suspension, and this was in either the unchanged form or as a pentapeptide metabolite. The apparent steady-state volume of distribution after intravenous bolus injection of leuprorelin in healthy men was 27 L. Volumes of distribution via subcutaneous or intramuscular injection have not been reported. The mean systemic clearance after intravenous administration of 1 mg leuprorelin in healthy men was 7.6–8.3 L/h.
The bioavailability of the sustained-release formulation after intramuscular injection is estimated to be approximately 90%.
The pharmacological effects of subcutaneous and intramuscular injection of leuprolide acetate sustained-release microspheres were investigated in rats and dogs. Following injection, the microspheres provided similar linear drug release and maintained serum drug concentrations for 3 months. In rats, administration of 100 μg/kg/day and in dogs, 25.6 μg/kg/day, resulted in sustained inhibition of serum luteinizing hormone and follicle-stimulating hormone levels, as well as serum testosterone levels in both rats and dogs, for more than 16 weeks. Results from periodic challenge tests showed that a single injection of the microspheres significantly inhibited the function of the pituitary-gonadal system in rats for 15 weeks. Reproductive organ growth was also inhibited in a dose-dependent manner for more than 3 months. Therefore, it is concluded that sustained-release leuprolide microspheres administered for 3 months provide a durable pharmacological effect.
This article reports the effect of formulation adjuvants on the absorption of leuprolide via duodenal injection and oral administration in male castrated rats. Compared with the intravenous control group, the absorption rates after oral and duodenal administration were approximately 0.01% and 0.08%, respectively. Aqueous formulations and water-in-oil emulsions of leuprorelin's lipophilic salt, decanesulfonic acid derivative, resulted in duodenal bioavailability of approximately 0.2% and 1%, respectively. Evaluation of the effects of formulations on oral absorption showed that the lipophilicity, surfactant, and excipient properties significantly influenced the duodenal absorption of leuprorelin. In typical emulsion systems, the absolute bioavailability of the drug was approximately 3–10%, which is about 100-fold higher than conventional methods. This article discusses the implications of these findings for the effects of formulation adjuvants on the oral absorption of leuprorelin and other peptide drugs after duodenal administration. This study compared the bioavailability of leuprorelin acetate in rats and healthy men (19–39 years old) after inhalation and intranasal administration, and compared it with intravenous and subcutaneous injection. α-Cyclodextrin, edicarboxylic acid, and solution volume all significantly improved the bioavailability of intranasal administration in rats. In vivo variability in animals ranged from 30% to 60%, with absorption rates ranging from 8% to 46% compared to the intravenously administered control group. In humans, the bioavailability of subcutaneous injection was 94%, higher than that of intravenous injection. The average bioavailability of intranasal administration was 2.4%, with significant inter-individual variability. The peak plasma concentrations for the 1 mg and 3 mg dose groups were 0.24–1.6 ng/ml and 0.1–11 ng/ml, respectively. The average peak plasma concentrations for the 1 mg aerosol and 2 mg suspension aerosol were 0.24–1.6 ng/ml and 0.1–11 ng/ml, respectively. The bioavailability of the suspension aerosol was four times that of the solution aerosol. /Leuprorelin Acetate/

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Metabolism/Metabolites
Radiolabeled studies showed that leuprorelin is primarily metabolized into inactive pentapeptides, tripeptides, and dipeptides, which may be further metabolized. Various peptidases encountered in systemic circulation are expected to be responsible for the metabolism of leuprorelin.

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Biological Half-Life
The terminal elimination half-life of leuprorelin is approximately three hours.

Hepatotoxicity
During leuprorelin treatment, mild serum enzyme elevations occur in 3% to 5% of patients, but elevations exceeding three times the upper limit of normal are rare, with a reported incidence of less than 1%. Serum enzyme elevations during leuprorelin treatment are usually transient and asymptomatic, resolving spontaneously with continued use, rarely requiring dose adjustment or discontinuation. Despite leuprorelin's decades of use, there are no confirmed cases of clinical liver injury reported. Routine monitoring for abnormal liver function tests is not recommended. Probability score: E (unlikely to be the cause of clinically significant liver injury). Protein Binding Leuprorelin binds to human plasma proteins in vitro at a rate of 43% to 49%. Interactions Objective: To evaluate the efficacy of etidronate sodium in combination with low-dose 19-nortestosterone-progestin norethindrone or high-dose norethindrone alone in preventing vasomotor instability and bone mineral density loss induced by GnRH agonist monotherapy. Methods: This randomized study enrolled 11 patients who received intramuscular injections of the long-acting GnRH agonist leuprorelin acetate 3.75 mg every 4 weeks for 24 weeks. Six patients (Group I) received oral etidronate sodium 400 mg daily for 14 days over three 56-day cycles, followed by oral calcium carbonate 500 mg daily for 42 days. This regimen was supplemented with oral norethindrone 2.5 mg daily. Five patients (Group II) received oral norethindrone 10 mg daily. Two control groups were included in this study. Group III consisted of ten previously reported patients who received only the same gonadotropin-releasing hormone agonist treatment. Group IV consisted of 12 treatment-untreated patients with regular menstrual cycles. Bone mineral density, vasomotor symptoms, circulating estrogen levels, and blood lipids were assessed sequentially. Results: Despite maintaining a persistently low estrogen state, the significant vasomotor dysfunction (P < .01) and decreased bone mineral density (-4.8 ± 0.9%; P < .05) observed in Group III patients were avoided in Groups I and II. Bone mineral density changes in Groups I and II were similar to those in the untreated control group (Group IV). A sustained decrease in high-density lipoprotein cholesterol (HDL-C) (P = .005) and an increase in the LDL/HDL-C ratio (P < .05) were observed only in Group II patients receiving high-dose norethindrone supplementation. Conclusion: These preliminary data suggest that adding cyclic etidronate sodium in combination with low-dose norethindrone to a GnRH agonist regimen is an effective method to mitigate the hypoestrogenic side effects induced by GnRH agonist monotherapy.

Drugs. 1994 Dec;48(6):930-67. doi: 10.2165/00003495-199448060-00008.

Therapeutic Uses
Anti-tumor drug, hormone; female fertility drug
Leuprorelin is indicated for palliative treatment of advanced prostate cancer, especially as an alternative to orchiectomy or estrogen therapy. /US product label includes/
Leuprorelin is indicated for the treatment of endometriosis, including pain relief and shrinkage of endometriotic lesions. /US product label includes/
Leuprorelin has approximately 30 times the activity of natural gonadotropin-releasing hormone and approximately 100 times that of gonadotropin-releasing hormone (gonadotropin).
For more complete data on the therapeutic uses of leuprorelin (15 in total), please visit the HSDB record page.
Drug Warnings
Patients sensitive to other synthetic gonadotropin-releasing hormone analogs may also be sensitive to leuprorelin.
Men: Suppression of testosterone production can lead to impaired fertility. While it is unclear whether fertility is restored after discontinuation of leuprorelin, the fertility suppression effect is usually reversed after discontinuation of similar analogs.
Use of leuprorelin during pregnancy is not recommended. Since the risk of fetal mortality is likely due to the hormonal effects of leuprorelin, it can be concluded that there is a risk of miscarriage when using leuprorelin during pregnancy.
It is currently unknown whether leuprorelin passes into breast milk. However, due to potential adverse effects on the infant, breastfeeding is generally not recommended while receiving leuprorelin treatment.
For more complete data on drug warnings for leuprorelin (14 in total), please visit the HSDB record page.

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Pharmacodynamics
Leuprorelin is a gonadotropin-releasing hormone (GnRH) analogue whose mechanism of action is as a GnRH receptor superagonist. Long-term use leads to a significant decrease in circulating steroid levels after the initial peak of GnRH-mediated steroid hormone (including testosterone and estradiol) production, consistent with the effects of other forms of androgen deprivation therapy (ADT). The corresponding hormone/steroid changes can produce specific adverse reactions in different patient populations. For women undergoing treatment for endometriosis or uterine fibroids, careful evaluation of pregnancy is recommended. An initial increase in estradiol levels may worsen symptoms such as pain and bleeding. Long-term use of leuprorelin is associated with decreased bone mineral density. Patients using leuprorelin in combination with norethindrone may experience sudden vision loss, proptosis, diplopia, migraines, thrombophlebitis, and pulmonary embolism, and may also have a higher risk of cardiovascular disease. Patients with a history of depression may experience a relapse of severe depressive symptoms. In men receiving palliative care for advanced/metastatic prostate cancer, a short-term increase in testosterone levels may lead to tumor recurrence and associated symptoms such as bone pain, hematuria, neuropathy, bladder and/or ureteral obstruction, and spinal cord compression. Furthermore, patients have an increased risk of hyperglycemia, diabetes, and cardiovascular disease, which may manifest as myocardial infarction, stroke, sudden cardiac death, or QT/QTc interval prolongation. Additionally, leuprorelin may cause seizures and embryo-fetal toxicity. In pediatric patients receiving treatment for central precocious puberty (CPP), a surge in initial steroid hormone levels may be associated with an increase in clinical signs of puberty within 2–4 weeks of treatment initiation. Additionally, leuprorelin may cause seizures and psychiatric symptoms, including irritability, agitation, aggression, anger, and crying.

C59H84N16O12

1209.42

1208.645

53714-56-0

74381-53-6 (monoacetate)

657181

Fluffy solid

1.4±0.1 g/cm3

150-155

1.682

0.41

15

14

32

87

2390

9

O=C([C@]([H])(C([H])([H])C([H])([H])C([H])([H])/N=C(\N([H])[H])/N([H])[H])N([H])C([C@]([H])(C([H])([H])C([H])(C([H])([H])[H])C([H])([H])[H])N([H])C([C@@]([H])(C([H])([H])C([H])(C([H])([H])[H])C([H])([H])[H])N([H])C([C@]([H])(C([H])([H])C1C([H])=C([H])C(=C([H])C=1[H])O[H])N([H])C([C@]([H])(C([H])([H])O[H])N([H])C([C@]([H])(C([H])([H])C1=C([H])N([H])C2=C([H])C([H])=C([H])C([H])=C12)N([H])C([C@]([H])(C([H])([H])C1=C([H])N=C([H])N1[H])N([H])C([C@]1([H])C([H])([H])C([H])([H])C(N1[H])=O)=O)=O)=O)=O)=O)=O)=O)N1C([H])([H])C([H])([H])C([H])([H])[C@@]1([H])C(N([H])C([H])([H])C([H])([H])[H])=O.O([H])C(C([H])([H])[H])=O

GFIJNRVAKGFPGQ-LIJARHBVSA-N

InChI=1S/C59H84N16O12/c1-6-63-57(86)48-14-10-22-75(48)58(87)41(13-9-21-64-59(60)61)68-51(80)42(23-32(2)3)69-52(81)43(24-33(4)5)70-53(82)44(25-34-15-17-37(77)18-16-34)71-56(85)47(30-76)74-54(83)45(26-35-28-65-39-12-8-7-11-38(35)39)72-55(84)46(27-36-29-62-31-66-36)73-50(79)40-19-20-49(78)67-40/h7-8,11-12,15-18,28-29,31-33,40-48,65,76-77H,6,9-10,13-14,19-27,30H2,1-5H3,(H,62,66)(H,63,86)(H,67,78)(H,68,80)(H,69,81)(H,70,82)(H,71,85)(H,72,84)(H,73,79)(H,74,83)(H4,60,61,64)/t40-,41-,42-,43+,44-,45-,46-,47-,48-/m0/s1

(2S)-N-[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2S)-1-[[(2R)-1-[[(2S)-1-[[(2S)-5-(diaminomethylideneamino)-1-[(2S)-2-(ethylcarbamoyl)pyrrolidin-1-yl]-1-oxopentan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-4-methyl-1-oxopentan-2-yl]amino]-3-(4-hydroxyphenyl)-1-oxopropan-2-yl]amino]-3-hydroxy-1-oxopropan-2-yl]amino]-3-(1H-indol-3-yl)-1-oxopropan-2-yl]amino]-3-(1H-imidazol-5-yl)-1-oxopropan-2-yl]-5-oxopyrrolidine-2-carboxamide

NSC-377526 NSC 377526 LeuprorelinA-43818 A 43818 A43818 NSC377526 leuprolide acetate Leuprorelinum Eligard

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)