Prediction of Aggregation In Vivo by Studies of Therapeutic Proteins in Human Plasma

Aggregation of human plasma and of human blood induced in vitro by filgrastim originator product; effect of PEGylation

We herein report that filgrastim product Neupogen® and the filgrastim formulation buffer induced aggregate formation when mixed in vitro with human plasma, and formation of large membranous erythrocyte aggregates when mixed with human blood, similar to the aggregation induced by pegfilgrastim and by pegfilgrastim buffer [T. Arvinte, E. Poirier, N. Ersayin, G. Darpin, A. Cudd, J. Dowd, S. Brokx, Aggregation of human plasma and of human blood induced in vitro by pegfilgrastim originator formulation buffer and pegfilgrastim products, Eur. J. Pharmaceut. Biopharmaceut. (2023), doi: 10.1016/j.ejpb.2023.10.019]. The data identify the filgrastim buffer (which is practically the same in filgrastim and pegfilgrastim products) as the main driver of human plasma and blood aggregation. Kinetic experiments showed differences in the extent of plasma aggregation induced by a filgrastim product manufactured in EU and one manufactured in USA. Human donor variability in the plasma aggregation induced by filgrastim was observed. To study the effect of PEGylation of the filgrastim protein on plasma aggregation we compared filgrastim (Neupogen®) with pegfilgrastim (Neulasta®) solutions at the same protein concentration. These data show that PEGylation has a beneficial effect in inhibiting to an extent plasma aggregation. Interestingly, 20 kDa polyethylene glycol in the filgrastim buffer induced more plasma aggregation compared to the buffer, similar to the aggregation induced by pegfilgrastim. For intravenous infusion filgrastim solutions (300 µg/ml, vials only) may be diluted in 5 % dextrose from a concentration of 300 µg/ml to 5 µg/ml. Aggregation of human plasma was also induced by filgrastim solutions diluted in 5 % dextrose to 50 µg/ml, 15 µg/ml and 5 µg/ml filgrastim, as well as by the filgrastim buffer similarly diluted in 5 % dextrose (1:6, 1:20 and 1:60 dilution). These data show that filgrastim solutions used for intravenous administration in patients induce human plasma aggregation in vitro. Such aggregation phenomena may be related to known infusion side effects of filgrastim therapy.

Defining the right diluent for intravenous infusion of therapeutic antibodies

Therapeutic monoclonal antibodies (mAbs) are commonly administered to patients through intravenous (IV) infusion, which involves diluting the medication into an infusion solution (e.g., saline and 5% dextrose). Using the wrong diluent can cause product aggregation, which may compromise patient safety. We and others have shown that Herceptin® (trastuzumab) and Avastin® (bevacizumab) undergo rapid aggregation upon mixing with dextrose and human plasma in vitro. In this study, we evaluated the compatibility of a panel of 11 therapeutic mAbs with dextrose or saline and human serum. These mAbs were randomly selected for their distinct formulations and IgG isotypes (IgG1, IgG2, IgG4, and Fc-fusion protein). All the mAbs appeared to be compatible with saline and human serum. However, mAbs that were formulated at acidic pH (≤ 6.5) exclusively formed insoluble aggregates upon mixing with dextrose and serum. Such aggregation was not detected for the mAbs that are at neutral pH (7.2–7.5) or in buffers containing sodium chloride. Mass spectrometric analysis revealed that the insoluble aggregates were composed of mAb molecules and several serum proteins (e.g., complement proteins, apolipoprotein, fibronectin) that are characterized by an isoelectric point of pH 5.4–6.7. At proximate pH to the isoelectric point values, those abundant serum proteins appeared to undergo isoelectric precipitation with mAb molecules. Our observations highlight a potential risk of protein aggregation at the blood-IV interface if a diluent is incompatible with a specific mAb formulation. This information has implications in guiding the design of product formulations and the selection of the right diluent for intravenous infusion of therapeutic mAbs.

Abbreviations: ADC: antibody-drug conjugate; D5W: 5% dextrose in water; IM: intramuscular; IV: intravenous; LC-MS/MS: liquid chromatography-tandem mass spectrometry; mAb: monoclonal antibody; SC: subcutaneous; pI: isoelectric point