Effect of polysorbate 80 quality on photostability of a monoclonal antibody.

Polysorbate 80 is one of the key components of protein formulations. It primarily inhibits interfacial damage of the protein molecule due to mechanical stress during shipping and handling. However, polysorbate 80 also affects the formulation photostability. Exposure to light of polysorbate 80 aqueous solution results in peroxide generation, which in turn may result in oxidation of the susceptible amino acid residues in the protein molecule. The purpose of this study was to determine if the photostability of our proprietary IgG(1) monoclonal antibody formulation containing polysorbate 80 is affected by the quality (grade/vendor) of polysorbate 80. Following four types of polysorbate 80 were tested: (1) Polysorbate 80 Super-Refined, Mallinckrodt Baker, (2) Polysorbate 80 NF, Mallinckrodt Baker, (3) Polysorbate 80 NF, EMD Chemicals, and (4) Ultra-pure Polysorbate 80 (HX), NOF Corporation. The samples were exposed to light as per ICH guidelines Q1B. The results of the study show that photostability of the antibody formulation is indeed affected by the quality of polysorbate 80. This study underscores the importance of carefully choosing the quality of polysorbate 80 to ensure the robustness of formulation.

L-Carnosine: multifunctional dipeptide buffer for sustained-duration topical ophthalmic formulations.

OBJECTIVES: The use of l-carnosine as an excipient in topical ophthalmic formulations containing gellan gum, a carbohydrate polymer with in-situ gelling properties upon mixing with mammalian tear fluid, was developed as a novel platform to extend precorneal duration. Specific utilisation of l-carnosine as a buffer in gellan gum carrying vehicles was characterised. METHODS: Buffer capacity was evaluated using 7.5, 13.3, and 44.2 mm l-carnosine in a pH range of 5.5-7.5. Accelerated chemical stability was determined by HPLC at l-carnosine concentrations of 5-100 mm. Combinations of 7.5 mm l-carnosine with 0.06-0.6% (w/v) gellan gum were characterised rheologically. l-Carnosine-buffered solutions of gellan gum were tested for acute topical ocular tolerance in vivo in pigmented rabbits. A unique formulation combining timolol (which lowers intraocular pressure) in l-carnosine-buffered gellan gum was compared with Timoptic-XE in normotensive dogs. KEY FINDINGS: l-Carnosine exhibited optimal pharmaceutical characteristics for use as a buffer in chronically administered topical ocular formulations. Enhancement trends were observed in solution-to-gel transition of l-carnosine-buffered vehicles containing gellan gum vs comparators. Topical tolerability of l-carnosine-buffered gellan gum formulations and lowering of intraocular pressure were equivalent with timolol and Timoptic-XE. CONCLUSIONS: Functional synergy between excipients in gellan gum formulations buffered with l-carnosine has potential for topical ocular dosage forms with sustained precorneal residence.

Effect of circulation on the disposition and ocular tissue distribution of 20 nm nanoparticles after periocular administration.

PURPOSE: Our previous studies indicated that while 20 nm particles are rapidly cleared from the periocular space of the rat following posterior subconjunctival injection, 200 nm particles persisted for at least two months. To understand faster clearance of 20 nm particles, the purpose of this study was to determine transscleral permeability and in vivo disposition in the presence and absence of circulation. Further, it was the purpose of this study to simulate sustained retinal drug delivery after periocular administration of rapidly cleared and slowly cleared nanoparticles. METHODS: The permeability of 20 and 200 nm particles over 24 h was examined across isolated bovine sclera and sclera-choroid-RPE with or without a surfactant (Tween 20, 0.1% w/v) added to the preparation. The in vivo disposition of nanoparticles was performed using Sprague Dawley rats. The rats, either dead or alive, were administered with 400 microg of the nanoparticles in the periocular space, and the particle disposition in the eye tissues was assessed 6 h later. To evaluate the role of the reticulo-endothelial system and lymphatic circulation, isolated liver, spleen, and cervical, axillary, and mesenteric lymph nodes were analyzed using confocal microscopy. Mathematical simulations with Berkeley Madonna were used to evaluate the effect of nanoparticle size on retinal drug levels following periocular administration. Celecoxib was used as the model drug and the finalized pharmacokinetic model from a previous study was used with some modifications for the simulation. RESULTS: Transport of 20 nm particles across sclera in the presence and absence of the surfactant were 0.1%+/-0.07% and 0.46%+/-0.06%, respectively. These particles did not permeate across the sclera-choroid-RPE in 24 h. There was no quantifiable transport for 200 nm particles across the sclera or the sclera-choroid-RPE. In live animals, the 20 nm particles were undetectable in any of the ocular tissues except in the sclera-choroid following periocular administration; however, in dead animals, the particle concentrations in the sclera-choroid were 19 fold higher than those in live animals, and particles were detectable in the retina as well as vitreous. The retention of 20 nm particles at the site of administration was two fold higher in the dead animals. In live animals, the particles were clearly detectable in the spleen and to a very low extent in the liver as well. The particles were also detected in the cervical, axillary, and mesenteric lymph nodes of the live animals. Simulations with two particles (20 nm and 200 nm) with different clearance rates demonstrated that the retinal drug levels were affected by particle clearance. Larger nanoparticles sustained retinal drug delivery better than smaller nanoparticles. With an increase in drug release rate from the particles, these differences diminish. CONCLUSIONS: The 20 nm particles are transported across the sclera to a minor degree; however, there is no significant transport across the sclera-choroid-RPE. Periocular circulation (blood and lymphatic) plays an important role in the clearance of the 20 nm particles. The higher particle levels in the ocular tissues in the post-mortem studies indicate a dynamic physiologic barrier to the entry of particles into the ocular tissues after periocular administration. The particle size of the delivery system can play an important role in the observed retinal drug levels after periocular administration. Slow release nanoparticles with low clearance by blood and lymphatic circulations are suitable for prolonged transscleral drug delivery to the back of the eye.