Understanding Phase Behavior of Nearly Energetically Equivalent Polymorphs To Achieve Controlled Crystallization for...

Area of Science:

• Pharmaceutical Sciences
• Solid-State Chemistry

Background:

• GENE-A, a Nav1.7 inhibitor with analgesic properties, was developed as a crystalline anhydrate.
• Two distinct polymorphic forms, Form I and Form II, were identified for GENE-A.

Purpose of the Study:

• To characterize the solid-state properties and determine the relative stability of GENE-A polymorphs.
• To evaluate thermodynamic and kinetic pathways for controlling polymorphic outcomes.
• To develop a scalable crystallization strategy for the desired solid form.

Main Methods:

• Solid-state characterization techniques were employed.
• Solubility measurements were conducted to assess thermodynamic stability.
• Competitive slurry experiments and crystallization studies were performed.

Main Results:

• Form I and Form II exhibited very similar free energies.
• Form II was determined to be the thermodynamically stable form above 25 °C.
• Form II was consistently obtained in competitive slurries at room temperature and in unseeded crystallization.
• Seeded crystallization experiments yielded variable results, with Form I forming under specific seeding conditions.

Conclusions:

• A controlled crystallization strategy using Form II as both starting material and seeds was developed.
• This strategy enables the reproducible production of the desired solid form upon scale-up.
• Understanding polymorphic behavior is crucial for consistent drug product manufacturing.