12 Investigator Site Networks Operating in the United States in 2026

A clinical investigator site network is where a trial actually happens: the physical location, staff, and principal investigator responsible for enrolling and treating patients according to protocol. Across the US, these networks take several forms, from purpose-built, multi-bed Phase 1 pharmacology units to community-based sites embedded inside primary care practices, to therapeutically focused networks built through acquisition and private equity investment.

The investigator site networks below are listed in no particular order and are all headquartered in the United States. Between them, these companies and providers cover diversity-focused multi-specialty networks, hospital-affiliated site models, purpose-built early-phase pharmacology units, decentralized and mobile trial models, and Integrated Research Organizations embedded inside large health systems.

Alcanza Clinical Research

Alcanza Clinical Research operates a network of 22 fully owned clinical research sites, six of which are embedded directly into active physician practices, with a name that translates from Spanish as "reach," reflecting its stated mission to expand access to underrepresented communities. Founded in 2021 and headquartered in Silver Spring, Maryland, the company runs trials across neurology, psychiatry, general medicine, vaccines, and cardiometabolic disease, with sites strategically located in areas with high concentrations of diverse patients. Alcanza maintains a dedicated Diversity, Equity, and Inclusion Committee that works to maintain demographic diversity across its site network and address language barriers for participants. The company expanded to Nevada in 2025 with the opening of Desert Clinical Research, part of a broader nationwide footprint that includes sites in Puerto Rico.

Alliance Clinical Network

Alliance Clinical Network (ACN) situates its research sites primarily on hospital campuses in cities with large minority populations, drawing on a proprietary recruitment model that has built a database of roughly 250,000 prequalified participants. Headquartered in Southlake, Texas, the company operates a network of wholly owned clinical research sites across Arizona, California, Florida, Nevada, New York, Pennsylvania, and Texas, running trials in CNS, dermatology, gastroenterology, internal medicine, metabolic conditions, pain, vaccines, and women's health. Amulet Capital Partners holds ACN as a portfolio company, backing its national expansion beyond its original Texas, California, and Nevada footprint. The network standardizes processes and technology across its wholly owned sites to compress study start-up timelines while maintaining consistent data quality.

Atlas Clinical Research

Atlas Clinical Research is a therapeutically driven, private-equity-backed clinical site network headquartered in Durham, North Carolina, specializing in infectious disease, CNS, gastroenterology, cardiovascular, metabolic, and general medicine research. The company, backed by private equity firm BPOC, has grown its portfolio through acquisitions including Rochester Clinical Research and Suncoast Clinical Research, with individual investigator sites it describes as centers of excellence built up over roughly 30 years of combined operating history. Atlas joined hyperCORE International's partner site network in April 2025, a shared alliance the company said would strengthen its North American reach alongside seven other independently operating research site organizations. The company continues expanding its footprint, including a planned new site in Buffalo, New York.

Care Access Research

Care Access Research operates a global network of research sites built around a decentralized model that brought mobile clinical trial units, including trucks and RVs staffed with full lab capabilities, to nursing homes during Eli Lilly's BLAZE-2 monoclonal antibody trial for COVID-19 in 2020. Founded in 2016 and headquartered in Boston, the company now operates roughly 50 locations across 12 countries, including the US, Canada, Brazil, and Poland, following its 2022 acquisition of IBPClin in Brazil and a 2025 acquisition of CEMEC, another Brazilian research center. Care Access offers sponsors three core services: a global site network, community health screenings to expand study reach, and on-demand staffing and space expansion support for existing research sites. A 2025 study co-authored by Care Access researchers found its decentralized, community-integrated site model produced higher randomization rates in a large neurodegenerative disease trial compared with traditional site models.

CenExel Clinical Research

CenExel Clinical Research operates 18 Centers of Excellence across major US metropolitan areas, formed in 2018 through the merger of JBR Clinical Research, a Salt Lake City facility specializing in analgesia and vaccine research, with ACMR, an Atlanta-based psychiatric research facility. The company's individual sites trace their operating history back more than 40 years, with its first site dating to 1982, and it has grown through both organic expansion and a series of acquisitions backed by Webster Equity Partners since 2019. CenExel's Centers of Excellence specialize in CNS and early-phase clinical research, alongside expertise in psychiatry, vaccines, neurology, analgesia, dermatology, sleep disorders, and ethnic bridging studies. Each center is staffed by Principal Investigator physicians the company says routinely meet or exceed sponsor patient recruitment goals.

Centennial Medical Group

Centennial Medical Group runs its clinical trial work through Centennial Research Center, a division embedded within its broader primary care and urgent care practice in Columbia, Maryland, drawing on a database of more than 100,000 patients who receive routine care at the practice. The research center has managed more than 160 clinical trials since 2003, spanning high-enrolling vaccine studies (including influenza, tetanus, meningitis, and zoster), diagnostic device studies, and internal medicine indications such as obesity, diabetes, and osteoporosis. Because the practice's research providers also see patients on the primary care side of the business, the company says it maintains a constant clinical presence that supports faster identification of trial-eligible patients. Centennial operates from four fixed locations plus mobile sites as needed, giving sponsors access to a population base built through decades of ongoing primary care relationships rather than newly recruited volunteers.

Flourish Research

Flourish Research operates a network of 24 clinical trial sites and roughly 150 investigators built by acquiring and integrating independently operating research sites, including platform companies Clinical Trials of Texas, Excel Medical Clinical Trials, Great Lakes Clinical Trials, and Clinical Site Partners. Headquartered in Apex, North Carolina, the company has conducted more than 3,700 trials across more than 15 therapeutic areas, with particular depth in cardiovascular, metabolic, neuroscience, and infectious disease research. In September 2024, private equity firm Genstar Capital made a strategic majority investment in Flourish, following an earlier growth phase backed by NMS Capital that took the company from a single-site model to its current multi-state footprint spanning Alabama, California, Florida, Illinois, North Carolina, Pennsylvania, Maryland, and Texas. Flourish positions its shared technology platforms and standardized processes as giving sponsors a single point of entry to what would otherwise be a fragmented site landscape.

Javara

Javara pioneered what it calls Clinical Research As A Care Option (CRAACO), an Integrated Research Organization model that embeds clinical trial staff and infrastructure directly inside large healthcare systems so patients can access trials through their existing physicians. The company's founding coincided with the onset of the COVID-19 pandemic, and its first major partnership, a 2021 Integrated Research Agreement with Atrium Health Wake Forest Baptist, extended clinical trial access across the health system's 24-county service area in northwest North Carolina and southwest Virginia. Javara and Wake Forest Baptist also partnered with Oracle and the US Department of Health and Human Services on a community-based COVID-19 study that helped researchers understand regional infection patterns during the pandemic. Headquartered in Winston-Salem, the company has since expanded its IRO model to additional health system partners beyond its original Wake Forest Baptist relationship.

Orlando Clinical Research Center

Orlando Clinical Research Center (OCRC) operates a custom-built, 35,000-square-foot facility specifically designed for Phase 1 clinical trials, featuring 100 in-house volunteer beds across 26 dorm-style rooms and a specialized treatment area with 12 hospital beds, six of which are plumbed for onsite hemodialysis. Led by president Dr. Thomas Marbury, the independent site runs Phase I–IV trials and has supported studies including a hepatitis C protease inhibitor trial evaluating danoprevir in combination therapy. OCRC's facility includes dual-lead digital telemetry monitoring with up to 25 leads, a card-key security system with digitally recorded cameras, and amenities intended to keep participants comfortable during multi-day inpatient stays. The center is located in Orlando's medical district with easy access to Orlando International Airport, supporting sponsors who need to fly in study monitors or specialized equipment.

Paradigm Clinical Research

Paradigm Clinical Research has connected people to clinical trials since 2009 and operates a growing network of wholly owned, purpose-built research sites across California, Colorado, and Idaho, with a stated mission of making trials more accessible to historically underrepresented communities. The company opened its first Idaho location in Boise in 2024, following a 2023 expansion into Littleton, Colorado that brought its site count to four at the time and added primary care physician Dr. Andy Fine as a principal investigator. Paradigm's purpose-built sites support Phase I–IV clinical trials across multiple medical specialties, offering both healthy volunteer studies and trials for people with specific health conditions. The company continues to expand into new communities, citing demand for study participants and the need for more diverse investigator representation as ongoing growth drivers.

Spaulding Clinical Research

Spaulding Clinical Research operates a 200-bed, fully paperless Clinical Pharmacology Unit in West Bend, Wisconsin, including 96 full 12-lead telemetry beds, in a facility the company says makes it the largest telemetry provider in the world. Founded in 2007 in a building that was originally a hospital, Spaulding specializes in First-in-Human, Single and Multiple Ascending Dose, and cardiac safety (Thorough QT) studies, and in 2020 was awarded a five-year, $5 million contract with the FDA's Division of Applied Regulatory Science to conduct clinical trials exploring drug-induced QT prolongation. The company expanded its service offerings to include ADME (absorption, distribution, metabolism, and excretion) studies in 2023. Spaulding's COO Joe Erato was named a 2024 Wisconsin Titan 100 honoree, recognizing business leaders driving growth across the state.

Triad Clinical Trials

Triad Clinical Trials operates out of a 3,000-square-foot, 1905 farmhouse near Guilford College in Greensboro, North Carolina, a historic building the company renovated and moved into in 2015 after establishing the site in 2007. The community-based research site has completed more than 150 Phase II–IV studies over roughly the past decade and has enrolled more than 5,000 patients across more than 20 medical categories since opening, with recent FDA audits in 2015 and 2017 returning no findings. Medical director Dr. Richard M. Montgomery and principal investigator Dr. William Hopper have together led more than 300 clinical studies at the site, working across virtually every medical discipline. The company has built longstanding relationships with sponsor companies, institutional review boards, and CROs that route studies to the Triad region of North Carolina.

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This article is intended as an informational overview of vendors operating in this space. Inclusion on this list does not constitute an endorsement, recommendation, or qualification by Diligent.