Stability-Indicating RP-HPLC Method Development and Validation of Lonafarnib in Pure and Pharmaceutical Dosage Forms

The pharmaceutical industry places high importance on the development of precise and reliable analytical methods to maintain drug quality and patient safety. Lonafarnib, a farnesyltransferase inhibitor, has garnered significant attention due to its therapeutic applications in treating progeria, a rare genetic disorder characterized by premature aging, and its potential in oncology. Ensuring the stability and efficacy of Lonafarnib in pharmaceutical products necessitates advanced analytical techniques capable of detecting the drug and its degradation products. Among these techniques, reverse-phase high-performance liquid chromatography (RP-HPLC) has emerged as a powerful tool due to its high precision, sensitivity, and adaptability to various formulations and matrices. Stability-indicating methods (SIMs) based on RP-HPLC are essential for regulatory compliance, enabling the accurate quantification of active pharmaceutical ingredients (APIs) and their degradation pathways. This review highlights the principles, methodologies, and challenges involved in the development and validation of RP-HPLC methods for Lonafarnib, with an emphasis on their practical applications in pharmaceutical dosage forms.

Lonafarnib is a farnesyltransferase inhibitor (FTI) primarily known for its role in treating Hutchinson-Gilford Progeria Syndrome (HGPS), a rare and fatal genetic disorder characterized by premature aging. Developed initially for oncology applications, Lonafarnib has demonstrated significant therapeutic benefits in addressing the underlying molecular pathology of progeria by inhibiting the farnesylation of progerin, a defective form of lamin A protein. The drug prevents the attachment of farnesyl groups to progerin, reducing its toxic accumulation in the nuclear envelope and mitigating cellular dysfunction.

In addition to its use in HGPS, Lonafarnib has shown potential in treating other conditions, such as hepatitis D virus (HDV) infections and certain types of cancer. Its ability to block the farnesylation process—a key post-translational modification involved in cell signaling and protein localization—has made it a versatile candidate in precision medicine. Lonafarnib is an oral medication, offering a convenient route of administration for chronic conditions. It is often formulated in combination with other agents to enhance its efficacy or target multiple pathways simultaneously. However, its therapeutic use necessitates rigorous quality control to ensure its stability and efficacy over time. This underscores the importance of robust analytical methods, such as reverse-phase high-performance liquid chromatography (RP-HPLC), for its quantification and stability assessment in both pure and pharmaceutical dosage forms. With its FDA approval for HGPS and ongoing research into broader applications, Lonafarnib represents a significant advancement in addressing unmet medical needs. Analytical and stability studies are crucial for optimizing its formulation and ensuring compliance with regulatory standards.

2. Importance of Stability-Indicating Methods

Stability-indicating methods are analytical procedures that effectively separate and quantify APIs and their degradation products. The significance of such methods lies in their ability to:
1. Assess the stability of drugs under various stress conditions (e.g., thermal, oxidative, photolytic, and hydrolytic).
2. Ensure the consistency of pharmaceutical formulations over their shelf life.
3. Detect and quantify impurities and degradation products, thereby supporting risk assessment and regulatory submissions.
The International Council for Harmonisation (ICH) guidelines, specifically Q1A(R2) for stability testing and Q2(R1) for analytical method validation, provide the foundation for developing SIMs. These guidelines mandate comprehensive forced degradation studies and the establishment of method performance characteristics to ensure reliability and reproducibility.

       
           
       
3. Method Development for Lonafarnib

RP-HPLC method development for Lonafarnib involves optimizing chromatographic conditions to achieve precise and reliable separation. Key aspects include:
**3.1 Chromatographic Considerations**
- Column Selection: C18 columns are commonly employed due to their hydrophobicity and ability to provide good resolution. Column dimensions typically range from 150–250 mm in length and 4.6 mm in diameter, with particle sizes of 3–5 µm.
- Mobile Phase Composition: The mobile phase usually consists of a combination of organic solvents (e.g., acetonitrile or methanol) and aqueous buffers (e.g., phosphate or acetate buffers). The pH is carefully adjusted (e.g., pH 3–7) to enhance separation and reduce peak tailing.
- Flow Rate: Optimized between 0.8 and 1.2 mL/min to balance resolution and runtime efficiency.
- Detection: UV or photodiode array detectors are commonly used. Lonafarnib exhibits maximum absorbance (?max) at 260–280 nm.
**3.2 Forced Degradation Studies**
Forced degradation studies are pivotal in determining the stability of Lonafarnib. Stress conditions applied include:
- Acid and Base Hydrolysis: Samples are treated with HCl or NaOH solutions to evaluate hydrolytic stability.
- Oxidation: Exposure to hydrogen peroxide (H2O2) to assess oxidative degradation.
- Thermal Stress: Samples are heated to temperatures up to 70°C to study thermal degradation.
- Photolysis: Samples are exposed to UV and visible light to test photostability.

4. Method Validation

Validation is conducted following ICH Q2(R1) guidelines to ensure method reliability. Key parameters include:
**4.1 Validation Parameters**
- Specificity: Ability to differentiate Lonafarnib from its impurities and degradation products, often tested using spiked samples.
- Linearity: Assessed by constructing calibration curves over a range of concentrations, ensuring correlation coefficients (R?2;) >0.99.
- Accuracy: Recovery studies typically range between 98–102%, indicating method accuracy.
- Precision: Repeatability and intermediate precision are evaluated, with relative standard deviation (RSD) <2> - Sensitivity: LOD and LOQ values are established to ensure the method's ability to detect low concentrations.
- Robustness: Variations in method parameters (e.g., flow rate, pH, mobile phase composition) are tested to confirm consistency.
**4.2 System Suitability Testing**
System suitability tests (SST) are integral to RP-HPLC method validation. Parameters such as retention time, theoretical plate count, resolution, and peak symmetry are monitored to ensure chromatographic performance.