In-Depth Comparison of Fasted State Simulated Intestinal Fluid (FaSSIF) Versions via NMR Spectroscopy and...

Area of Science:

• Pharmaceutical Sciences
• Analytical Chemistry
• Physical Chemistry

Background:

• Efficient early drug development requires accurate simulation of the small intestine's absorption environment.
• Fasted State Simulated Intestinal Fluid (FaSSIF) versions V2 and V3 are crucial for mimicking these conditions, with updated formulations aiming for greater physiological relevance.
• Understanding drug and polymer interactions within these simulated fluids is key to predicting oral drug absorption.

Purpose of the Study:

• To investigate the molecular-level aggregation behavior and interactions of model drugs (carbamazepine, ketoconazole, efavirenz) and polymers within FaSSIF-V2 and FaSSIF-V3 using NMR spectroscopy.
• To elucidate the impact of formulation differences between FaSSIF-V2 and FaSSIF-V3 on diffusion behavior and analytical outcomes.
• To compare the robustness and suitability of FaSSIF-V2 and FaSSIF-V3 for drug interaction studies.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy, including Diffusion Ordered Spectroscopy (DOSY), was employed to study molecular interactions and diffusion.
• Solubility measurements and Dynamic Light Scattering (DLS) were used to characterize the media and particle behavior.
• Molecular Dynamics (MD) simulations were performed to complement experimental findings and provide deeper mechanistic insights.

Main Results:

• Individual FaSSIF versions exhibited different diffusion behaviors, which were normalized upon addition of drugs or polymers.
• FaSSIF-V3's complex composition led to increased spectral overlap and challenges in DOSY analysis due to co-existing species with varying solubilities.
• Model drugs displayed distinct interaction profiles, ranging from minimal interaction (carbamazepine) to full incorporation into bile aggregates (efavirenz).
• Differences in diffusion behavior between FaSSIF-V2 and FaSSIF-V3 were attributed to solubility variations in lecithin-like molecules.

Conclusions:

• FaSSIF-V2 demonstrated greater robustness across multiple analytical techniques compared to FaSSIF-V3, despite FaSSIF-V3 offering a closer mimic of the natural intestinal environment.
• NMR spectroscopy, combined with other methods, provides valuable molecular-level insights into drug behavior in simulated intestinal fluids.
• FaSSIF-V2 is a reliable and robust medium for studying drug-excipient interactions in early drug development, offering consistent results across different analytical approaches.