Pemetrexed Liquid Formulation Stability via Antioxidant Chelation
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Solution Overview
Problem
Pemetrexed formulations have limited long-term stability due to rapid degradant formation, especially under acidic and alkaline conditions, which prevents the development of commercially viable ready-to-use liquid formulations with extended storage stability.
Innovation Solution
The development of liquid pemetrexed formulations incorporating an antioxidant like lipoic acid or methionine, a chelating agent such as sodium citrate, and up to 75% propylene glycol, maintaining a pH range of 8 to 9.5, which significantly reduces impurities and enhances storage stability for at least 18 months at temperatures from 5°C to 25°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pemetrexed is formulated as a ready-to-use liquid formulation, then ease of operation is improved, but storage stability deteriorates due to rapid degradant formation
Solution Approach 1:
The patent applies preliminary action by pre-formulating pemetrexed in a stable liquid composition containing antioxidants (e.g., ascorbic acid, alpha-tocopherol), chelating agents (e.g., EDTA, citrate), and buffer systems at optimized pH (6.5-7.5). These stabilizing agents are incorporated in advance to prevent degradation during storage, enabling the formulation to maintain stability for at least 6 months at 25°C without requiring lyophilization or complex packaging modifications.
Solution Approach 2:
The patent applies parameter changes by optimizing the pH of the formulation to a narrow range of 6.5-7.5, which minimizes degradant formation. Additionally, the formulation controls oxidative conditions through antioxidants and chelating agents, and adjusts ionic strength and composition to prevent hydrolysis. These parameter optimizations enable the liquid formulation to achieve enhanced storage stability while maintaining ease of use.
2Stability of the object's composition
If antioxidants and chelating agents are added to prevent degradation, then storage stability is improved, but device complexity increases
Solution Approach 1:
The patent applies merging by combining multiple stabilizing functions into a single integrated liquid formulation. Antioxidants (e.g., ascorbic acid, alpha-tocopherol), chelating agents (e.g., EDTA, citrate), and buffer systems are merged into one homogeneous composition that simultaneously prevents oxidation, chelates metal ions, and maintains pH stability. This unified approach simplifies manufacturing and packaging compared to separate components, while providing comprehensive protection against degradation.
Solution Approach 2:
The patent applies self-service by designing a self-stabilizing formulation where the antioxidants, chelating agents, and buffers work synergistically to maintain stability without requiring external intervention. The formulation automatically resists oxidation, chelates trace metals, and maintains pH within the optimal range through its inherent composition, eliminating the need for complex packaging systems or additional stabilization steps during storage and handling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The formulations demonstrate substantial long-term stability with less than 5% total impurities after 18 months, and preferably less than 1% after 2 years, maintaining effective drug content and preventing degradation, thus addressing the limitations of current pemetrexed formulations.
Implementation Method 1
an antioxidant such as lipoic acid, dihydrolipoic acid, methionine and mixtures thereof
Implementation Method 2
a chelating agent such as lactobionic acid, sodium citrate, tribasic (tri sodium citrate dihydrate) and mixtures thereof
Data Source
AI summary
Long term storage stable pemetrexed-containing liquid pharmaceutical compositions are disclosed. The compositions can include pemetrexed or pharmaceutically acceptable salts thereof; an antioxidant selected from lipoic acid, dihydrolipoic acid, methionine and mixtures thereof; a chelating agent selected from lactobionic acid, sodium citrate, tribasic and mixtures thereof; and a pharmaceutically acceptable fluid. The pH of the compositions is in a range of about 8 to about 9.5. The pemetrexed-containing compositions have less than about 5% total impurities, on a normalized peak area response (“PAR”) basis as determined by high performance liquid chromatography (“HPLC”) at a wavelength of 227 nm, after at least about 18 months of storage at a temperature of from about 5° C. to about 25° C. Methods of preparing the formulation as well as methods of treatment of pemetrexed-susceptible diseases using the same are also disclosed.