Arginine glutamate

Thermal stability attributes including unfolding onset (T_onset) and mid-point (T_m) are often utilized for efficient development of monoclonal antibody (mAb) products during lead selection and formulation screening workflows. An assumption of direct correlation between thermal and kinetic physical stability underpins this basic approach. While literature reports have substantiated this general approach under specific conditions, clear exceptions have been highlighted alongside. Herein, a set of mAbs formulated under diverse solution conditions to generate a broad array of thermal and kinetic stability profiles were systematically analyzed. Sequence modifications in the Fc region were purposefully engineered to generate a set of low-melting mAbs. A diverse set of excipients were subsequently utilized and shown to modulate the T_m over a wide range. While a general correlation between high T_m and low aggregation rate was observed under accelerated conditions, the predictive utility of T_m under relevant product storage conditions was inadequate at best. Critically, T_m data did not correlate with long-term aggregation rates under refrigerated or room temperature conditions. Even under accelerated conditions, T_m appeared to be a poor predictor of aggregation once it exceeded the solution storage temperature (40°C) by ∼15°C, similar to conditions routinely encountered in the development of canonical mAbs (T_m > 60°C). Pitfalls of simplistic correlative approaches are discussed in the context of practical biologics product development.

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.