Sustained-release hot melt extrudates of the weak acid TMP-001: A case study using PBB modelling.

Over the last 30 years, hot melt extrusion has become a leading technology in the manufacture of amorphous drug delivery systems. Mostly applied as an 'enabling formulation' for poorly soluble compounds, application in the design of sustained-release formulations increasingly attracts the attention of the pharmaceutical industry. The drug candidate TMP-001 is currently under evaluation for the early treatment of Multiple Sclerosis. Although this weak acid falls into class II of the Biopharmaceutics Classification System, the compound exhibits high solubility in the upper intestine resulting in high peroral bioavailability. In the present studies, four different formulation prototypes varying in their sustained-release behavior were developed, using L-arginine as a pore-forming agent in concentrations ranging between 0 and 20%. Initially, biorelevant release testing was applied to assess the dissolution behavior of the prototypes. For these formulations, a total drug release of 44.7%, 64.6%, 75%, and 90.5% was achieved in FaSSIF-v2 after 24 h. Two candidates were selected for further characterization considering the crystal structure and the physical stability of the amorphous state of TMP-001 in the formulations together with the release behavior in Level II biorelevant media. Our findings indicate L-arginine as a valuable excipient in the formulation of hot melt extrudates, as its presence led to a considerable stabilization of the amorphous state and favorably impacted the milling process and release behavior of TMP-001. To properly evaluate the proposed formulations and the importance of colonic dissolution and absorption on the overall bioavailability, a physiologically-based biopharmaceutics model was used.