Amino acid-based stable adalimumab formulation in spray freeze-dried microparticles for pulmonary delivery

Adalimumab is a monoclonal antibody that neutralizes tumor necrosis factor-alpha (TNF-alpha), which is involved in chronic inflammatory diseases including asthma. We aimed to prepare porous adalimumab microparticles with appropriate aerodynamic properties and stability for inhalable therapy. Adalimumab formulations were processed through spray freeze-drying (SFD) in the presence of amino acids. The effects of leucine, phenylalanine, glycine, and arginine on the physicochemical stability of adalimumab were studied by mass spectrometry, microchip electrophoresis, circular dichroism, UV spectrophotometry, and size-exclusion chromatography. The aerodynamic behavior of SFD-processed powders was assessed using a two-stage impinger. Biological activity of the adalimumab formulations was assessed using fibroblast L-929 cells. The microparticles prepared by SFD were highly porous, spherical, and 8-12 mu m in diameter. The amino acids ensured the stability of adalimumab during the SFD process as well as over a 3-month storage period at 40 degrees C and 75% relative humidity. The stability results were well correlated with those of biological activity obtained in L-929 cells. Deterioration in the stability of adalimumab resulted in decreased biological activity. The adalimumab formulations containing leucine or phenylalanine exhibited the best aerodynamic performance. Thus, SFD-processed adalimumab prepared with leucine or phenylalanine could provide inhalable microparticles useful for anti-TNF-alpha therapy.