Background and importance Efficacy and safety of emerging biosimilars is ensured by the comparative studies required for their centralised approval by the European Medicines Agency. However, there is a lack of studies of biosimilars safety in clinical practice. Recently a new biosimilar bevacizumab, Zirabev, has been commercialised.

Aim and objectives To assess the safety of bevacizumab biosimilar Zirabev in clinical practice.

Material and methods We conducted a prospective observational study of a cohort of patients who started treatment with bevacizumab biosimilar between February and July 2021 at the Oncology Service of the health organisation Barrualde-Galdakao in a Basque health institution.

Eligible patients: new bevacizumab treatments, treatment restarts, changes in line of treatment and ovarian, cervix and brain carcinoma pathologies maintenances. Switching has done in treatments already started from Avastin to Zirabev.

Information was collected in a database from medical records. Adverse reactions were measured according to National Cancer Institute of the United States toxicity criteria.

Results Between February 2021 and July 2021, 27 adult patients started bevacizumab biosimilar treatment in our centre. Baseline characteristics of the patients (N = 27): female 22 (81.5%); age 57.5 ± 13.7 years (mean ± SD); baseline blood pressure (mmHg) 124.3 ± 18.2/78.0 ± 7.2. Neoplasia ovarian 8 (29.6%), cervix 2 (7.4%), colon 9 (33.3%), brain 3 (11.1%), breast 5 (18.5%). Days with bevacizumab biosimilar treatment: 112.7 ± 46.9. Switching from reference medicine to biosimilar: 11 (40.7%). New bevacizumab treatments: 16 (59.3%).

Adverse events (G = grade) in switching patients (N=11): G1 epistaxis 2, G1 gingival haemorrhage 1.

Adverse events in starting treatments: G1 arterial hypertension 1, G2 arterial hypertension 3, G3 venous thrombosis 1, G3 arterial thromboembolism (pulmonary) 2.

Most frequent adverse event was hypertension (14.8%, N=27, G1–2). Thrombotic-like events were the most serious reactions (11.1%, N=27, G3).

Only one patient stopped bevacizumab treatment due to toxicity (G3 pulmonary embolism and G3 deep vein thrombosis).

Conclusion and relevance Initiation of use of bevacizumab biosimilar in our centre has shown a positive safety profile. Thrombotic-like reactions were more severe compared to the literature. Nevertheless, there were no serious adverse events (G4–5).

References and/or acknowledgements Common Terminology Criteria for Adverse Events (CTCAE) Version 5.0. 27 November 2017.

Conflict of interest No conflict of interest