Biosimilars may be able to increase treatment access for traditionally excluded communities, especially racial and ethnic minority populations.
Even with clear clinical guidelines present, former studies show that up to 28% of patients with monoclonal antibody human epidermal growth factor receptor 2 (ERBB2)-overexpressing early-stage breast cancer do not receive ERBB2-targeted therapy, and that cost is the greatest cited hurdle, especially in low- and middle-income countries, according to a review in JAMA Network Open.
The United States also perceives racial inequities whereby Black patients, who are disproportionately laden with financial toxicity and other structural blocks to cancer care, are less likely to receive reference trastuzumab, an ERBB2 antagonist.
Biologics like trastuzumab are the fastest growing medication class in the country and make up a growing portion of health care costs.
Biosimilars hold the possibility to reduce or worsen health inequalities depending on if studies supporting regulatory approval dismiss marginalized populations and could impact external validity and if update continues across racial and ethnic populations. Introduction of trastuzumab biosimilar SB3 (Ontruzant) could save costs and promote access.
“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,” said the researchers.
Therefore, the researchers affixed a health equity lens to the assessment of biosimilar safety while considering long-term follow-up studies of oncology biosimilars and their corresponding external validity relative to health equity.
The authors cited a report (Pivot et al) assessing the results of a phase 3 randomized trial of SB3, a trastuzumab biosimilar approved by the FDA in 2019, in the largest and longest follow-up study to date comparing cardiac safety and survival with its originator, reference trastuzumab.
The primary outcomes present in this cardiac safety investigation were incidences of symptomatic congestive heart failure and asymptomatic significant decrease in left ventricular ejection fraction with a median follow-up of 68 months.
A subset of 367 participants in the phase 3 trial who were supervised for cardiac safety outcomes, wherein no symptomatic congestive heart failure was seen in either the SB3 or trastuzumab groups and only 3 asymptomatic significant left ventricular ejection fraction decreases were reported, with 1 in the SB3 group and 2 in the trastuzumab group.
The cohort primarily consisted of White and Asian American patients and did not include any Black or Latin American (Latinx) patients. Additionally, although 20% of the cohort was Asian American, very few were of South Asian descent.
These findings came in stark contrast with the significantly increased risk of congestive heart failure (relative risk [RR], 5.11; 90% CI, 3.00-8.72; P < .00001) and left ventricular ejection fraction decline (RR, 1.83; 90% CI, 1.36-2.47; P = .0008) reported in a meta-analysis or prior trastuzumab clinical trials.
Pivot et al indicated that the reasons for lower rates of cardiac events in this setting include cardiac monitoring procedures with early stopping issues, and stringent inclusion criteria for the study. The overall presence of cardiovascular disease (coronary artery disease, 3.90%) and conditions representing cardiovascular risk factors (obesity, 4.46%; diabetes, 2.60%; and hypercholesterolemia, 1.12%) were very low.
Even though an absence of serious cardiac events seen over 5 years of follow up is heartening, researchers are becoming more and more cognizant of cancer treatment-related cardiotoxic effects when reviewed in clinical practice, where cardiovascular risk factor rates and cardiovascular mortality are substantially higher and disproportionately affect historically marginalized racial and ethnic groups.
This study adds necessary pharmacovigilance data on Asian patients with breast cancer, a group seen to have higher risk of ERBB2-overexpressing breast cancer in the US, because approximately 20% of patients in both the control and treatment groups were of Asian descent.
“However, no Black or Latinx participants were included in this biosimilar safety analysis, and few South Asian participants were represented, all of which are populations with higher rates of cardiovascular morbidity and high incidence of cardiovascular toxic effects following anti–ERBB2-targeted therapies,” said the researchers.
In 2022, the FDA announced draft guidance on diversity plans to improve participant enrollment from historically excluded communities in clinical trials and will signify a mandate for drug sponsors in 2024.
Prior to conducting a study, the researchers emphasize that enrollment can be optimized by prioritizing health equity and include historically excluded racial and ethnic populations in the beginning in the prospective evidence generation life cycle.
Some limitations of study consisted of the lack of external validity for Black and Latinx patients who are both at higher risk of cardiovascular toxic effects and have the least access to ERBB2-targeted therapy and may have the most possible benefit from increased affordability.
“We highlight the potential of empirical data for retrospective and prospective evidence generation to address a root cause of persistent cancer health inequities,” concluded the researchers.
Calip GS, Altomare IP, Guadamuz JS. Evaluating external validity of oncology biosimilar safety studies. JAMA Netw Open. Published online April 6, 2023. Accessed July 18, 2023. doi:10.1001/jamanetworkopen.2023.5776