molecular formula C26H37N5O2 B1668192 Cabergoline CAS No. 81409-90-7

Cabergoline

Cat. No.: B1668192
CAS No.: 81409-90-7
M. Wt: 451.6 g/mol
InChI Key: KORNTPPJEAJQIU-KJXAQDMKSA-N
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Description

Cabergoline is a long-acting, ergot-derived dopamine D2 receptor agonist with high selectivity and potency. Its pharmacokinetic profile, characterized by a prolonged half-life (~68 hours), enables infrequent dosing (e.g., twice weekly), improving patient compliance compared to shorter-acting agonists like bromocriptine . Approved for hyperprolactinemia, it is also used off-label in acromegaly, Parkinson’s disease (PD), and peripartum cardiomyopathy (PPCM). This compound suppresses prolactin (PRL) secretion, reduces growth hormone (GH) and insulin-like growth factor 1 (IGF-I) levels, and mitigates dopaminergic deficiency in PD. Its safety profile is favorable at therapeutic doses, though high doses historically raised concerns about cardiac valve fibrosis, a risk mitigated in newer analogs .

Properties

IUPAC Name

(6aR,9R,10aR)-N-[3-(dimethylamino)propyl]-N-(ethylcarbamoyl)-7-prop-2-enyl-6,6a,8,9,10,10a-hexahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide
Source PubChem
URL https://pubchem.ncbi.nlm.nih.gov
Description Data deposited in or computed by PubChem

InChI

InChI=1S/C26H37N5O2/c1-5-11-30-17-19(25(32)31(26(33)27-6-2)13-8-12-29(3)4)14-21-20-9-7-10-22-24(20)18(16-28-22)15-23(21)30/h5,7,9-10,16,19,21,23,28H,1,6,8,11-15,17H2,2-4H3,(H,27,33)/t19-,21-,23-/m1/s1
Source PubChem
URL https://pubchem.ncbi.nlm.nih.gov
Description Data deposited in or computed by PubChem

InChI Key

KORNTPPJEAJQIU-KJXAQDMKSA-N
Source PubChem
URL https://pubchem.ncbi.nlm.nih.gov
Description Data deposited in or computed by PubChem

Canonical SMILES

CCNC(=O)N(CCCN(C)C)C(=O)C1CC2C(CC3=CNC4=CC=CC2=C34)N(C1)CC=C
Source PubChem
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Description Data deposited in or computed by PubChem

Isomeric SMILES

CCNC(=O)N(CCCN(C)C)C(=O)[C@@H]1C[C@H]2[C@@H](CC3=CNC4=CC=CC2=C34)N(C1)CC=C
Source PubChem
URL https://pubchem.ncbi.nlm.nih.gov
Description Data deposited in or computed by PubChem

Molecular Formula

C26H37N5O2
Source PubChem
URL https://pubchem.ncbi.nlm.nih.gov
Description Data deposited in or computed by PubChem

Related CAS

85329-89-1 (diphosphate)
Record name Cabergoline [USAN:USP:INN:BAN]
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DSSTOX Substance ID

DTXSID6022719
Record name Cabergoline
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Molecular Weight

451.6 g/mol
Source PubChem
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Description Data deposited in or computed by PubChem

Physical Description

Solid
Record name Cabergoline
Source Human Metabolome Database (HMDB)
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Description The Human Metabolome Database (HMDB) is a freely available electronic database containing detailed information about small molecule metabolites found in the human body.
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Solubility

Insoluble, 6.40e-02 g/L
Record name Cabergoline
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Record name Cabergoline
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CAS No.

81409-90-7
Record name Cabergoline
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Record name Cabergoline [USAN:USP:INN:BAN]
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Record name (6aR,9R,10aR)-N-[3-(dimethylamino)propyl]-N-(ethylcarbamoyl)-7-prop-2-enyl-6,6a,8,9,10,10a-hexahydro-4H-indolo[4,3-fg]quinoline-9-carboxamide
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Record name CABERGOLINE
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Record name Cabergoline
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Melting Point

102-104 °C, 102 - 104 °C
Record name Cabergoline
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Record name Cabergoline
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Explanation HMDB is offered to the public as a freely available resource. Use and re-distribution of the data, in whole or in part, for commercial purposes requires explicit permission of the authors and explicit acknowledgment of the source material (HMDB) and the original publication (see the HMDB citing page). We ask that users who download significant portions of the database cite the HMDB paper in any resulting publications.

Preparation Methods

Synthetic Routes and Chemical Synthesis

Starting Materials and Initial Protection Steps

Cabergoline synthesis typically begins with ergoline-8β-carboxylic acid esters, such as methyl or ethyl esters, which are derived from ergot alkaloids. The initial step involves protecting the indole nitrogen and secondary amine functionalities to prevent undesired side reactions. A preferred method employs tert-butyl carbamate (Boc) to protect the indole nitrogen, forming a stable intermediate (compound VII). Sodium hexamethyldisilazide (NaHMDS) is used as a strong base to deprotonate the amide nitrogen, enabling subsequent trapping with phenyl chloroformate to yield a phenyl carbamate intermediate (compound VIII). This dual protection strategy ensures regioselectivity during subsequent reactions.

Amidation and Urea Formation

The protected ergoline derivative undergoes amidation with 3-(dimethylamino)propylamine to extend the side chain. This reaction is facilitated by aprotic solvents such as tetrahydrofuran (THF) at temperatures ranging from −50°C to reflux. The resulting amide (compound IV) is then reacted with ethyl isocyanate to form the urea moiety, a critical structural feature of this compound. Silylating agents like trimethylsilyl trifluoromethane sulfonate (TMSOTf) are employed to activate intermediates, enhancing reaction efficiency.

Deprotection and Final Modification

Final deprotection of the Boc group is achieved under acidic conditions, typically using hydrochloric acid in methanol. The liberated secondary amine is subsequently alkylated with an allyl alcohol derivative to introduce the allyl group at position 6 of the ergoline backbone. This step completes the synthesis of this compound’s core structure. The overall process achieves a yield of approximately 78%, significantly higher than earlier methods that reported yields below 50%.

Crystallization and Polymorphic Forms

Solvent-Dependent Polymorphism

This compound exhibits multiple crystalline forms, each with distinct physicochemical properties. Form I, the most thermodynamically stable polymorph, is industrially preferred due to its consistent bioavailability. Patent literature describes two primary methods for obtaining Form I:

  • Toluene/Diethyl Ether Solvate Route : Crystallization from a toluene-diethyl ether mixture at −20°C yields Form V, a toluene solvate, which is subsequently desolvated under vacuum to produce Form I. This method, however, suffers from a low yield (45%) and requires prolonged drying.
  • Ethylbenzene-Based Crystallization : Dissolving this compound in ethylbenzene at 25–30°C followed by cooling to −23°C produces a solvate that is easily converted to Form I via nitrogen drying. This approach improves yields to 86% and reduces particle size variability (Table 1).

Table 1: Comparison of Crystallization Methods for this compound Form I

Method Solvent System Temperature (°C) Yield (%) Particle Size (X₅₀, µm)
Toluene/Diethyl Ether Toluene + Ether −20 45 15–20
Ethylbenzene Ethylbenzene −23 86 5–10

Alternative Polymorphs and Their Applications

Form II, characterized by a melting point of 108°C, is obtained by stirring this compound in diethyl ether for several days. Form VII, a metastable polymorph, is generated by suspending Form I in n-heptane or 1,4-dioxane for 48 hours. While these forms are less common in pharmaceutical products, they serve as intermediates in purity optimization.

Industrial-Scale Production and Yield Optimization

Solvent Selection and Process Efficiency

The shift from toluene to ethylbenzene as the primary crystallization solvent addresses key industrial challenges. Ethylbenzene’s higher volatility facilitates faster drying, reducing processing time from 29 hours to under 15 hours. Additionally, its low toxicity profile aligns with modern green chemistry principles.

Particle Size Control

Milling, a traditional method for particle size reduction, often induces polymorphic transitions. The ethylbenzene-derived Form I exhibits a median particle size (X₅₀) of 5–10 µm without milling, compared to 15–20 µm for toluene-based methods. This finer particle size enhances dissolution rates, critical for oral bioavailability.

Formulation Considerations

Oral Liquid Preparation

This compound’s poor aqueous solubility necessitates specialized formulations. A standard oral liquid (500 µg/mL) is prepared by dissolving this compound in propylene glycol (10 mL) and adding tutti frutti flavoring agents. The solution is homogenized to ensure uniformity, with stability studies confirming a shelf life of 30 days under refrigeration.

Analytical Characterization

Chromatographic Purity

High-performance liquid chromatography (HPLC) analyses reveal that ethylbenzene-derived Form I achieves 99.9% purity, surpassing the 98.5% purity of toluene-based methods. Impurities predominantly include residual solvents (<0.1%) and des-allyl metabolites (<0.05%).

Thermal Stability

Differential scanning calorimetry (DSC) of Form I shows a single endothermic peak at 101.5°C, indicative of high crystalline purity. In contrast, Form II exhibits dual melting events due to polymorphic contamination.

Chemical Reactions Analysis

Cabergoline undergoes various chemical reactions, including hydrolysis and oxidation. It is highly sensitive to hydrolysis, particularly at the urea moiety and amide group. The alkene bond in this compound is susceptible to oxidation. Common reagents used in these reactions include water for hydrolysis and oxidizing agents for oxidation. The major products formed from these reactions are degradation products identified using infrared and mass spectrometry analyses.

Scientific Research Applications

Treatment of Hyperprolactinemia

Overview : Cabergoline is the first-line treatment for hyperprolactinemia, effectively normalizing prolactin levels in a significant percentage of patients.

Key Findings :

  • In a study involving 455 patients, this compound normalized serum prolactin levels in 86% of cases. Specifically, normalization was achieved in 92% of patients with idiopathic hyperprolactinemia or microprolactinoma and 77% in those with macroadenomas.
  • Tumor shrinkage was observed in 67% of patients, while visual field abnormalities improved in 70% .

Treatment of Pituitary Adenomas

Overview : this compound not only suppresses hormone production but also induces tumor shrinkage in prolactinomas.

Research Insights :

  • Recent studies indicate that this compound may suppress tumor cell proliferation and induce apoptosis through novel mechanisms. This suggests potential applications in treating other tumors beyond pituitary adenomas, including breast cancer and pancreatic neuroendocrine tumors.

Acromegaly Management

Overview : this compound is also utilized in managing acromegaly, particularly in patients who have not undergone radiation therapy.

Clinical Efficacy :

  • In non-irradiated patients, this compound normalized insulin-like growth factor 1 (IGF-1) levels in approximately 32% of cases. However, biochemical control (normal IGF-1 and growth hormone levels) was achieved in only 13% .

Potential Use in Other Tumors

Recent research has explored this compound's broader applications in oncology:

  • Breast Cancer : Studies suggest that this compound may have anti-tumor effects on breast cancer cells, potentially offering a new therapeutic avenue for treatment.
  • Neuroendocrine Tumors : Its efficacy has been investigated for pancreatic neuroendocrine tumors, indicating possible benefits in tumor management.

Case Studies and Clinical Trials

Several case studies illustrate the efficacy and safety profile of this compound:

Study TypePatient PopulationOutcome
Retrospective Cohort Study455 patients with hyperprolactinemia86% normalization of prolactin levels
Clinical TrialNon-irradiated acromegaly patients32% normalization of IGF-1 levels
Case SeriesPatients with breast cancerIndications of tumor growth suppression

Mechanism of Action

Cabergoline exerts its effects by stimulating dopamine D2 receptors, which are G-protein coupled receptors associated with Gi proteins. In lactotrophs, stimulation of dopamine D2 receptors inhibits adenylyl cyclase, decreasing intracellular cyclic adenosine monophosphate (cAMP) concentrations and blocking inositol triphosphate (IP3)-dependent release of calcium from intracellular stores. This results in the inhibition of prolactin secretion .

Comparison with Similar Compounds

Cabergoline is compared to bromocriptine, somatostatin analogs (SSA), and pegvisomant (PEG) across indications. Key findings are summarized below:

Hyperprolactinemia

Comparison with Bromocriptine

Parameter This compound Bromocriptine Evidence Source
Dosing Frequency 0.5–2 mg twice weekly 2.5–5 mg daily
PRL Normalization 95.7% efficacy 80.9% efficacy
Time to PRL Control 3–6 months Slower (6–12 months)
Adverse Events 10.6% (nausea, headache) 15–30% (nausea, hypotension, vomiting)
Patient Tolerance Superior due to fewer GI side effects Higher discontinuation rates

Key Findings :

  • This compound achieves faster PRL normalization and higher efficacy with fewer side effects .
  • A randomized trial (n=94) showed this compound improved LH, FSH, and estradiol levels more effectively than bromocriptine, enhancing menstrual regularity .

Acromegaly

Comparison with Bromocriptine and SSA

Parameter This compound Monotherapy Bromocriptine Monotherapy This compound + SSA Evidence Source
IGF-I Normalization 34% (baseline IGF-I <750 ng/mL) <20% 52% (SSA-resistant cases)
GH Suppression 48.5% reduction (1–2 mg/week) Limited efficacy at high doses Synergistic with SSA
Dosing Convenience Oral, twice weekly Oral, multiple daily doses Requires SSA injections
Cost Lower than SSA/PEG Low Higher (SSA component)

Key Findings :

  • This compound monotherapy is effective in one-third of patients, particularly with mild IGF-I elevation .
  • When added to SSA, this compound normalizes IGF-I in 50% of SSA-resistant cases, regardless of prolactin levels .
  • Superior to bromocriptine in tolerability and efficacy, though less potent than SSA or PEG .

Parkinson’s Disease

Comparison with Bromocriptine and Levodopa

Parameter This compound Bromocriptine Levodopa Evidence Source
Motor Improvement Similar UPDRS scores Similar UPDRS scores Superior efficacy
Levodopa Sparing Reduces dose by 20–30% Comparable reduction N/A
Adverse Events Confusion (↑), somnolence Hypotension, nausea Dyskinesias (↑↑)
Dosing Once daily Three times daily Multiple doses

Key Findings :

  • This compound and bromocriptine show comparable motor improvement, but this compound’s once-daily dosing improves adherence .
  • Confusion is more frequent with this compound, while bromocriptine has higher gastrointestinal toxicity .

Peripartum Cardiomyopathy (PPCM)

Comparison with Bromocriptine

Parameter This compound Bromocriptine Evidence Source
HF Prevention 100% recovery in small series Effective in preclinical models
Safety No major adverse events reported Risk of thrombosis

Key Findings :

  • Both agents prevent postpartum heart failure in mouse models, but this compound’s safety in humans requires validation in larger trials .

Metabolic Effects

Comparison with Placebo (Obesity/Prediabetes)

Parameter This compound Placebo Evidence Source
Glucose Tolerance Improved postprandial glucose/insulin No change
Weight Loss 1.2% body weight 1.0% body weight

Key Findings :

  • This compound improves glucose metabolism independent of weight loss, suggesting dopaminergic modulation of insulin sensitivity .

Biological Activity

Therapeutic Applications

This compound is utilized in various clinical contexts, including:

  • Hyperprolactinemia :
    • A retrospective study involving 455 patients showed that this compound normalized prolactin levels in 86% of cases, with significant improvements noted in visual field abnormalities and tumor shrinkage.
    • The median starting dose was 1.0 mg/week, which could be reduced to 0.5 mg/week upon achieving control.
  • Acromegaly :
    • In a study of 64 patients, this compound treatment resulted in plasma IGF-I suppression below 300 µg/L in 39% of cases, indicating its potential role in managing acromegaly by reducing growth hormone levels.
    • Tumor shrinkage was observed in 13 out of 21 patients with GH-/PRL-cosecreting adenomas.
  • Cushing's Disease :
    • This compound has shown promise in treating Cushing's disease, with a case study reporting cortisol normalization in approximately 40% of patients after three months of treatment.

Neuroprotective Effects

Recent research suggests that this compound may also possess neuroprotective properties:

  • A study indicated that this compound prevents oxidative stress-induced neuronal cell death by reducing extracellular glutamate accumulation and inhibiting ERK1/2 signaling pathways. This suggests potential applications beyond endocrine disorders, possibly extending into neurodegenerative conditions.

Case Studies and Research Findings

StudyPopulationOutcomeKey Findings
Odaka et al. (2014)Cortical neuronsNeuroprotectionPrevented oxidative stress-induced cell death via D2 receptor activation.
De Smet et al. (2008)455 patients with hyperprolactinemiaProlactin normalizationAchieved normalization in 86% of cases; effective across various adenoma types.
Colao et al. (2008)64 acromegalic patientsIGF-I suppressionSuppressed IGF-I below 300 µg/L in 39% of cases; tumor shrinkage noted.
Petrossians et al. (2001)Patients with Cushing's diseaseCortisol normalizationNormalization achieved in 40% after three months; significant tumor size reduction observed.

Q & A

Basic Research Questions

Q. What experimental models are appropriate for investigating Cabergoline’s dopamine receptor selectivity and mechanism of action?

  • Methodological Answer : Utilize in vitro competitive binding assays with radiolabeled dopamine receptors (D2 and D5 subtypes) to measure this compound’s affinity and intrinsic activity. Dose-response curves can quantify receptor activation thresholds. In vivo models (e.g., rodent prolactinoma) should measure serum prolactin suppression as a functional endpoint. Ensure assays include controls for cross-reactivity with other receptors (e.g., serotonin) to confirm specificity .

Q. How can researchers determine the optimal this compound dose for prolactin suppression in hyperprolactinemia?

  • Methodological Answer : Conduct dose-escalation studies in animal models or clinical cohorts, measuring serum prolactin levels weekly. Use nonlinear mixed-effects modeling (NONMEM) to correlate dose with hormonal response, adjusting for covariates like body weight and baseline prolactin. Validate findings with pharmacokinetic/pharmacodynamic (PK/PD) simulations to identify minimal effective and maximal tolerated doses .

Q. What biomarkers are validated for monitoring this compound’s therapeutic efficacy in endocrine disorders?

  • Methodological Answer : IGF-I normalization (for acromegaly) and prolactin suppression (for hyperprolactinemia) are primary biomarkers. Secondary endpoints include tumor volume reduction (MRI) and patient-reported outcomes (e.g., headache resolution). Ensure assays meet CLIA/CAP certification standards to minimize variability .

Advanced Research Questions

Q. How can researchers reconcile contradictory findings on this compound’s association with valvular heart disease?

  • Methodological Answer : Apply multivariate Cox regression in large-scale cohort studies to adjust for confounders (e.g., age, hypertension, cumulative dose). Stratify analyses by dose thresholds (e.g., <3 mg/week vs. ≥3 mg/week) and validate echocardiographic endpoints (e.g., valve thickening) with blinded adjudication. Meta-analyses should assess publication bias via funnel plots and Egger’s test .

Q. What statistical approaches are suitable for analyzing this compound’s synergistic effects with somatostatin analogs in acromegaly?

  • Methodological Answer : Use interaction terms in mixed-effects regression models to evaluate additive vs. synergistic effects on IGF-I suppression. Individual patient data (IPD) meta-analyses can pool data from heterogeneous studies, adjusting for baseline IGF-I, tumor size, and prolactin levels. Sensitivity analyses should exclude outliers to ensure robustness .

Q. How to design longitudinal studies evaluating this compound’s long-term neuroendocrine and cardiovascular outcomes?

  • Methodological Answer : Implement a prospective, matched cohort design with annual echocardiography and hormonal profiling. Use time-dependent covariates in survival analysis to account for cumulative exposure. Power calculations should assume a 5% annual incidence of subclinical valvulopathy, requiring ≥500 patient-years of follow-up .

Q. Methodological Considerations

  • Contradiction Analysis : When studies report conflicting results (e.g., valvulopathy risk), perform subgroup analyses by dose, duration, and population characteristics. Use the Bradford Hill criteria to assess causality .
  • Research Design : For preclinical studies, adhere to ARRIVE guidelines for experimental rigor. In clinical research, prioritize randomized adaptive trials for dose-finding and PROBE designs for long-term safety .

Retrosynthesis Analysis

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Feasible Synthetic Routes

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