Trastuzumab-qyyp Maintains Stability and Potency Under Extended In-Use Conditions

Researchers using “a range of structural analytical techniques and a functional bioassay” found that biosimilar trastuzumab-qyyp is stable and maintains its biological activity under extended in-use conditions. They said that the findings, which were published in the Journal of Oncology Pharmacy Practice, are consistent with results from other studies on the reference product (Herceptin) and other trastuzumab biosimilars.

Pfizer Europe MA EEIG’s trastuzumab biosimilar (Trazimera) was granted marketing authorization for all indications of the originator by the European Medicines Agency (EMA) in 2018 and was approved by the FDA in 2019. Trastuzumab is a recombinant monoclonal antibody to human epidermal growth factor receptor 2 (HER2). It is used to treat metastatic breast cancers and gastric cancers that overexpress HER2, either as monotherapy or together with other therapies.

Although trastuzumab provides “significant clinical benefit” in these conditions, the authors said, a “substantial portion” of patients with HER2-positive metastatic breast cancer in the United States and Europe don’t receive trastuzumab therapy. They cited surveys of physicians that identified barriers to trastuzumab prescription as primarily cost-related. The authors said the development of trastuzumab biosimilars could expand access to patients who could benefit from HER2-targeted therapy.

Extended in-use conditions

The investigators explained that trastuzumab requires dilution in 0.9% sodium chloride before it is administered to patients, and it is typically recommended to use the diluted trastuzumab within 24 hours “due to concerns with microbiological contamination.” However, they wrote, this is not necessarily the case in clinical practice, where “infusion solutions are often prepared well in advance of use,” and “robust data on product stability under extended in-use conditions would be beneficial to accommodate scheduling and logistics.”

The investigators followed guidelines established by The Specialist Pharmacy Service of the National Health Service (NHS) in the United Kingdom for assessing the stability of a biologic, which included measurement of the product’s physicochemical stability and biological activity. They tested trastuzumab-qyyp “over a range of concentrations and time periods that may be encountered prior to administration, using a wide range of analytical and cell-based techniques.”

To simulate possible storage conditions in a clinical setting, the biosimilar was diluted in 0.9% sodium chloride to concentrations ranging from 0.2 mg/ml to 4 mg/ml in 3 different types of infusion bags (polyolefin, ethylene vinyl acetate, and polyvinyl chloride), and stored for 24 hours at 25°C, followed by storage for 0, 1, 2, 4, or 6 weeks at between 2°C and 8°C.

Physicochemical characteristics and biological activity

No differences in visual characteristics were detected between samples, and there were “no substantial changes” in the pH of any of the samples over time, though the authors observed higher variability in pH in lower-concentration samples. They also reported no changes in protein concentration over the storage period, suggesting that there was “minimal” protein adsorption to the plastic infusion bags.

The investigators found no significant differences in molecular weight or charge variants for any of the concentrations, time points, and infusion bags they tested. The proportion of intact antibody was greater than 85% in all samples, and the authors found no evidence of an increase in antibody fragmentation over time.

Peptide mapping of the 4 mg/ml samples suggested no change in the primary structure of the protein during storage. The authors added that the “high degree of similarity between the chromatograms also indicates that no significant post-translational modification” occurred over the 6 weeks of storage. Further analysis of the 4 mg/ml samples found no indication of a change in the secondary structure or thermal stability of the protein throughout the study.

The authors wrote the degree of methionine oxidation of the antibody “remained consistently low throughout the study, with most samples showing <5% oxidation.” However, they added that low-concentration samples in ethylene vinyl acetate infusion bags showed higher levels of oxidation than those in polyolefin or polyvinyl chloride bags.

Cation-exchange chromatography demonstrated no significant change in relative abundance of the main charge species, or acidic or basic variants, over the course of the study.

Finally, biological activity of the antibody, as assessed using a cell-based growth inhibition assay, demonstrated that the relative potency of the biosimilar was maintained during the time in storage.

The authors concluded, “the physicochemical stability and biological activity of [trastuzumab-qyyp] was maintained following dilution and storage for 24 h at 25±5° C and then an extended period of up to 6 weeks at 2–8° C.” They added that their results were similar to those from previous studies on the reference product and other trastuzumab biosimilars.

Reference

Weiser S, Burns C, Zartler ER. Physicochemical stability of PF-05280014 (trastuzumab-qyyp; TrazimeraTM), a trastuzumab biosimilar, under extended in-use conditions. J Oncol Pharm Pract. 2022 Jan 24:10781552221074649. doi:10.1177/10781552221074649.