Background: Bispecific antibodies (bsAbs), such as epcoritamab (CD3×CD20 for DLBCL; FDA-approved May 2023) and elranatamab (BCMA×CD3 for MM; FDA-approved August 2023), represent rapidly expanding treatment options, especially for relapsed/refractory disease. However, the geographic distribution of bsAb clinical trials across the United States has not been systematically characterized with respect to disease incidence, Medicaid penetration, racial and ethnic composition, or rurality, despite their potential to influence equitable access to these therapies.

Methods: We identified all U.S.-based bsAb trials in DLBCL and MM registered on ClinicalTrials.gov from 2015 through 2024. Trial site locations were mapped by state and county. We compared site distribution to state-level, age-adjusted DLBCL/MM incidence (using SEER data) and to Medicaid managed care penetration as of July 2022 (based on KFF state Medicaid reports). Counties were classified by urban/rural status (2010 RUCA codes) and by racial/ethnic majority (from American Community Survey data). We calculated trial-site density per 1,000 incident cases in each state and used logistic regression to estimate odds of a county hosting a bsAb trial site based on racial/ethnic majority, rurality, and Medicaid metrics, adjusting for local incidence rates.

Results: We identified 127 unique U.S. bsAb trial sites for DLBCL and MM, including representative trials such as NCT04649359, NCT04824794, and ISB-1342 studies. Over 60% of sites were concentrated in only 10 metropolitan counties. States with Medicaid expansion generally had higher Medicaid managed care penetration rates (≥80% of eligible enrollees) compared with non-expansion states (averaging ~60%).

Majority-Black and majority-Hispanic counties were markedly less likely to host bsAb trial sites even after adjusting for incidence and insurance coverage: majority-Black counties had nearly threefold lower odds of hosting any trial (adjusted OR ~0.33; p<0.01), and majority-Hispanic counties had roughly twofold lower odds (adjusted OR ~0.52; p=0.02). Rural counties showed significantly lower odds of hosting a bsAb site compared with urban counties (adjusted OR ~0.28; p<0.001).

Trial-site density per 1,000 incident cases was highest in northeastern states like Massachusetts and New York (>0.20 sites per 1,000 cases) but lowest in several southern, non-Medicaid-expansion states (e.g., Alabama, Mississippi, New Mexico), where density fell below 0.05 sites per 1,000 cases. Notably, sponsor diversity was limited: three pharmaceutical companies accounted for approximately 70% of all bsAb trial sites, with some states only offering single-sponsor or investigator-initiated studies.

Conclusion: This is the first quantitative, population-based analysis showing that bsAb trial access for DLBCL and MM is significantly skewed toward urban, high-income, majority-White counties with higher Medicaid-managed care penetration and located in Medicaid-expansion states. Disadvantaged counties (majority-Black/Hispanic, rural, lower Medicaid reach) are dramatically underrepresented. Given that bsAbs like epcoritamab and elranatamab were FDA approved in 2023, this contemporary gap risks perpetuating inequities in access to cutting-edge immunotherapies. These disparities warrant urgent sponsor and policy level interventions, including incentives for trial placement in underserved areas, representation quotas, and Medicaid alignment. These concerns may be further exacerbated by proposed federal legislation in 2025 aimed at reducing Medicaid coverage and rural health infrastructure, which could widen existing gaps in trial access for historically marginalized populations.

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2025
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