Evaluating External Validity of Oncology Biosimilar Safety Studies
- Biologics are the fastest growing medication class in the US, significantly contributing to healthcare costs.
- The Biologics Price Competition and Innovation Act of 2009 created an abbreviated approval pathway to make biological products more accessible.
- A phase 3 randomized trial of SB3, a trastuzumab biosimilar, showed no symptomatic congestive heart failure and minimal asymptomatic left ventricular ejection fraction decrease compared to its originator product.
- Despite clinical guidelines, up to 28% of patients with ERBB2-overexpressing early-stage breast cancer do not receive targeted therapy, primarily due to cost barriers.
- Racial inequities exist in the US, with Black patients less likely to receive trastuzumab due to financial and structural barriers.
- Oncology biosimilars like SB3 have the potential to reduce costs and increase access to treatment, particularly for patients facing financial barriers.
- The study noted a lack of representation of Black, Latinx, and South Asian participants, who have higher cardiovascular morbidity and toxicity risks.
- External validity concerns include generalizability and transportability of the study findings to a broader, more diverse population.
- Data equity is crucial for capturing diverse experiences and ensuring equitable health outcomes. The FDA released draft guidance to improve diversity in clinical trial enrollment, which will be mandated by 2024.
- Empirical data can address gaps in data equity and improve clinical trial diversity, impacting the generalizability and transportability of findings.
Biologics are the fastest growing medication class in the US and account for an increasing portion of health care costs. In the US, the Biologics Price Competition and Innovation Act of 2009 created an abbreviated approval pathway to expand access to safe and effective biological products. Pivot et al report the results of a phase 3 randomized trial of SB3, a trastuzumab biosimilar approved by the US Food and Drug Administration (FDA) in 2019, in the largest and longest follow-up study to date comparing cardiac safety and survival with its originator product, reference trastuzumab. Trastuzumab is a monoclonal antibody human epidermal growth factor receptor 2 (ERBB2) antagonist indicated for treatment of ERBB2-overexpressing breast cancer.
Use of ERBB2-targeted therapy is the standard of care for patients with ERBB2-overexpressing tumors in most clinical scenarios. Despite clear clinical guidelines, previous studies indicate that up to 28% of patients with ERBB2-overexpressing early-stage breast cancer do not receive ERBB2-targeted therapy and that cost of treatment is the greatest reported barrier, especially in low-income and middle-income countries. In the US, there are also racial inequities, whereby Black patients, who are disproportionately burdened with financial toxicity and other structural barriers to cancer care, are less likely than their White counterparts to receive trastuzumab. The entry of oncology biosimilars such as SB3 into a stable, competitive market represents a potential for cost savings and increased access to these treatments, especially among patients for whom cost is a barrier to receipt of optimal therapy. Here, we apply a health equity lens to the evaluation of biosimilar safety and consider long-term follow-up studies of oncology biosimilars and their corresponding external validity in relation to health equity.
As with other medical advances, biosimilars have the potential to reduce or exacerbate health inequities depending on whether studies supporting regulatory approval exclude marginalized populations as commonly occurs, thus impacting external validity, and whether uptake remains disparate across racial and ethnic populations.
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