Role of arginine salts in preventing freezing-induced increase in subvisible particles in protein formulations

While arginine hydrochloride (ArgHCl) has emerged as a potential stabilizer of protein drugs in liquid formulations, the purpose of this manuscript was to evaluate its stabilization potential in frozen solutions. The phase behavior of frozen ArgHCl solutions was investigated by differential scanning calorimetry and low temperature powder X-ray diffractometry. The aggregation of β-galactosidase was evaluated following freeze-thaw cycling in ArgHCl solutions with and without mannitol. ArgHCl (5% w/v) was retained amorphous in frozen aqueous solutions and effectively inhibited protein aggregation even after 5 freeze-thaw cycles. Annealing frozen arginine solution (5% w/v) containing mannitol (10% w/v) induced mannitol crystallization which in turn facilitated crystallization of ArgHCl. The stabilizing effect of ArgHCl was completely lost in the presence of mannitol. Use of alternate arginine salts (aspartate, glutamate, and acetate) allowed selective crystallization of mannitol while arginine was retained amorphous and stabilized the protein.