Phase IV pharmacovigilance study of biosimilar drugs in cancer: A Colombian cohort.

e23348 Background: Biosimilar drugs are essential for improving access to treatments in developing countries, reducing costs without compromising efficacy. Assessing their safety profile compared to innovator drugs is crucial to ensure equivalent outcomes in clinical practice. Methods: We conducted a single-arm cohort study using medical records at two exposure-based time points, innovator and biosimilar drug. The objective was to evaluate adverse drug reactions (ADR) incidence and analyze correlations with ADR groups. Statistical analyses considered variable normality, with non-parametric tests used of three related groups to identify significant associations. Results: A total of 21 patients were included in the study, receiving treatment with bevacizumab (57%), rituximab (24%), and trastuzumab (19%). Data were analyzed across two periods, resulting in 42 data points and 29 reported ADR events. For innovator drugs, the ADR incidence was 71.5% (15 events), with 26% involving multiple ADRs. Common toxicities were neurological (47%), gastrointestinal (40%), musculoskeletal (27%), dermatological (13%), and others (13%). Primarily ADRs were grade 2 or 3 (CTCAE), with two grade 4 events (rituximab and bevacizumab). ADRs occurred in 100% of trastuzumab patients, 83% with bevacizumab, and 20% with rituximab (P = 0.01), no infusion reactions were reported. Among ADR cases, 57% were on concomitant therapy. Median ADR development times were 8 months for trastuzumab (CI: 95% 1-8), 6 months for bevacizumab (CI: 95% 1-13), and 6 months for rituximab (CI: not calculable), with no significant differences. For biosimilars, the ADR incidence was 66% (14 events), with 43% involving multiple ADRs. Common toxicities included gastrointestinal (57%), dermatological (35%), neurological (14%), fatigue (14%), and others (35%). Primarily ADRs were grade 2 or 3 (CTCAE), with one grade 4 event (bevacizumab). ADRs occurred in 92% of bevacizumab patients, 40% with rituximab, and 25% with trastuzumab (P = 0.01), with one infusion reaction reported for rituximab. Among ADR cases, 76% were on concomitant therapy. Median ADR development times were 5 months for rituximab (CI: nc), 3 months for trastuzumab (CI: nc), and 2 months for bevacizumab (CI: 95% 1-2), with no significant differences. The incidence of ADRs was compared between biosimilar drugs and innovator drugs, resulting in a P-value of 0.2. Conclusions: Biosimilars demonstrated a comparable safety profile comparable to innovator drugs, with no significant differences in ADR incidence. Trastuzumab biosimilars showed a trend toward lower ADR incidence and bevacizumab biosimilars exhibited a higher incidence, though not statistically significant. These results support their safe use in Colombia, highlighting the need for further studies on cost-effectiveness, long-term safety, and real-world efficacy, especially in diverse and low-income populations.