Comparison of the physicochemical properties of a biosimilar filgrastim with those of reference filgrastim.

Recombinant human granulocyte-colony stimulating factor (filgrastim) is a therapeutic protein used primarily to reduce incidence and duration of severe neutropenia and its associated, and serious, complications. We have developed a biosimilar filgrastim (Hospira filgrastim; Nivestim) designed to be comparable to Amgen filgrastim (Neupogen). An extensive characterization study assessed the physiochemical similarity of Hospira filgrastim to Amgen filgrastim. Both drugs were supplied in 1 ml glass, single-use, prefilled syringes (five batches of each product at 480 microg/0.5 ml and one batch of each product at 300 microg/0.5 ml). Samples were evaluated using state-of-the-art analytical methods (validated in accordance with International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use or Pharmeuropa guidelines) to determine physicochemical properties, molecular characteristics, purity and biological activity. Samples were compared after long-term storage at 2-8 degrees C and storage at 40 degrees C (stress conditions) to evaluate their degradation impurity profiles. Hospira filgrastim and Amgen filgrastim were shown to have similar physicochemical properties, molecular characteristics, purity and biological activity. No significant differences in product-related impurities were recorded between Hospira filgrastim and Amgen filgrastim following storage for 12 weeks under stress conditions. These data show that the physicochemical profile of Hospira filgrastim is similar to that of Amgen filgrastim.

Low temperature properties of lyophilized solutions and their influence on lyophilization cycle design: pentamidine isethionate.

Pentamidine isethionate is a lyophilized antiprotozoal drug. Its solutions, when lyophilized, have been found to exhibit a range of properties that depend on its concentration and the manner in which it is allowed to freeze. These properties were examined by Differential Scanning Calorimetry (DSC), freeze-drying microscopy and X-ray powder diffraction. In DSC studies, the drug exhibited eutectic behavior with a eutectic temperature of -2.8 degrees C. Freeze-drying microscopic examination of a sample of solution after cooling at about 1 degrees C/min showed that the sample dried with retention up to -4 degrees C, where melting was observed. By using the appropriate drug concentration and manipulating the freezing stage, crystallization of the drug from solution could be induced during cooling to yield a crystalline end-product.

Effect of Entrapped Markers on the in situ Jejunal Uptake from Liposomal Systems.

The effect of entrapped PEG-4000, inulin, and insulin on thein situuptake from the rat jejunum of liposomes was determined. Each of these markers greatly reduced or completely eliminated jejunal uptake unless the liposomes were repeatedly "washed" to remove marker from the external bilayer surface. Addition of free marker to a suspension of empty liposomes resulted in complete loss of liposomal uptake. It appears that "inert" markers can profoundly affect the rate and extent of liposomal uptake from the rat jejunum and the preparative technique employed can greatly affect the behavior of the system.

Monolayer studies of insulin-lipid interactions.

The interactions between insulin and various lipids were studied by monolayer penetration experiments at constant surface area. The increase in surface pressure, delta II, of a lipid film depended upon the particular lipid used and the concentration of insulin in the subphase. For all lipids studied, delta II was dependent on the initial surface pressure of the lipid film. Evidence of the interaction between insulin and the lipids was found in the ability of insulin to penetrate lipid films with initial pressures greater than 16 dynes/cm, the maximum surface pressure obtained by insulin alone. For phospholipids, both the nonpolar and polar regions influenced the degree of interaction with insulin. Saturated chain lecithins exhibited less penetration than phospholipids with unsaturated hydrocarbon chains. The net charge of the lipid was not found to be an important determinant of penetration; however, the structure of the polar group can have a dramatic effect. Insulin penetration of mixed lipid films cannot be predicted by the penetration characteristics of the pure components. The possible role of these interactions in determining the geography of the insulin molecule within the liposome and its resultant effects on the stability is discussed.

Effect of Ca2+ on thermotropic properties of saturated phosphatidylcholine liposomes.

The effect of various concentrations of calcium ion (Ca2+) on dipalmitoylphosphatidylcholine (DPPC), distearoylphosphatidylcholine (DSPC) and mixed DPPC/DSPC (1:1) liposomes was studied by differential scanning calorimetry. Ca2+ concentrations of 10 mM and above split the main transition peak of DPPC into two distinguishable components, and, at 30 mM and above, also resulted in the disappearance of a pre-transition peak. The effect of Ca2+ on DSPC liposomes was even more dramatic in that it induced a more definitive split in the main transition peak and caused the loss of the pretransition peak at only 10 mM concentration. The thermograms of the DPPC/DSPC mixed liposomes were unaltered in the presence of Ca2+, even at a concentration of 50 mM. Whether or not Ca2+ is able to alter thermograms of phosphatidylcholine liposomes appears to be dependent on the degree of molecular order of the bilayer prior to interaction with Ca2+.