Experience, Longevity, Quality and Service.

CenExel Centers of Excellence offer world-class quality and experience. CenExel CNS champions that standard.

CenExel CNS provides cutting-edge treatment while advancing medical research.

With two large campuses in Long Beach, CA, Garden Grove, CA, and Torrance, CA, CenExel CNS is a leading clinical research organization that conducts studies in a wide variety of therapeutic areas. CenExel CNS’s highly trained and experienced staff, including four board certified clinical investigators, is dedicated to maintaining the highest standard of quality results in the trials they conduct.

Hundreds of clinical trials conducted since 2010.
View Current Studies
CenExel CNS offers 27,000 square feet of facility space with several dedicated units.
CenExel CNS exceeds 100% of patient target in recruitment.
Full-service, Phase I CRO capabilities provided through strategic partnerships.
CenExel CNS centralizes budgeting and contracting for faster study start-up.
group of people
CenExel CNS serves a broad and diverse demographic.

Center Leadership

Debra Hoffmeyer

David Walling, Ph.D.

Chief Clinical Officer

Dr. Walling co-founded Collaborative Neuroscience Research (CNS) in 2000 to advance medical knowledge through the execution of clinical trials. His operational and strategic leadership has enabled the growth of CNS into one of the largest clinical research providers in the US. He is a principal investigator for many studies at the inpatient unit in Long Beach as well as the outpatient clinic in Garden Grove. Dr. Walling advises pharmaceutical companies in numerous ways including the creation of drug development plans, design and analysis of clinical trials in all phases, and preparation for interactions with regulatory agencies.

Work History

Dr. Walling has served as an investigator in over 600 trials, including over 100 Phase I trials, with many focusing on schizophrenia and cognition, areas in which he is recognized as a thought leader.

Before founding CNS, Dr. Walling was VP of Clinical Services at Psychiatric Management Resources & Stadt Solutions Pharmacy Corporation. He has also served as an Assistant Professor and Research Scientist in Psychiatry and Behavioral Sciences at the University of Texas Medical Branch at Galveston. Dr. Walling has clinical experience as a licensed psychologist and marriage, family, and child counselor.

Dr. Walling has authored dozens of articles on psychiatric indications that have been published in leading scientific journals. Dr. Walling also provides training to rater training companies for some of the most widely used psychiatric and cognitive rating scales including the Positive and Negative Syndrome Scale (PANSS).

Dr. Walling is a highly sought-after KOL in psychiatry and in digital device and software technologies. His pioneering work in small proof of concept studies within Phase I development programs has ensured the successful path for several drugs. He holds multiple advisory board memberships and consulting positions for sponsors.

Dr. Walling received his doctorate in Counseling Psychology from the University of Southern California. He attended California State University, Long Beach, earning a master’s degree in Counseling as well as a bachelor’s degree in Psychology.

David Poling

Dalia Botros, MD, MBBS

Chief Operating Officer

Dr. Botros joined CNS in 2008, bringing in over 10 years’ experience in clinical research. She leads operations for all CNS’s locations, ensuring policies and procedures are optimized and continuously reviewed to exceed the highest standards of industry expectations. Dr. Botros works relentlessly to achieve effective project planning and operational management for each trial. She makes sure that clinical research activities are fully compliant with federal regulations and ICH/GCP guidelines.

Work History

Prior to being elevated to her current role in 2020, Dr. Botros served as Director of Operations for the CNS Long Beach site for 10 years. She led the CNS Clinical Pharmacology Unit expansion to support both healthy normal volunteers and patient populations in early phase clinical trials and developed the associated standard operating procedures. From 2008 to 2010, Dr. Botros was Site Director for CNS’s Torrance site, managing the day-to-day operations of the research clinic and supervising the clinical team. Prior to joining CNS, Dr. Botros worked in Dermatology Research as a Clinical Research Fellow, completing almost 50 studies for over 20 pharmaceutical companies. Earlier on, she was a General Physician at the Alexandria Medical University Hospital as well as an obstetrician/Gynecologist at the Kafr Dawar Public Hospital in Alexandria, Egypt. Dr. Botros has published numerous clinical studies and poster presentations and has been a guest speaker for a variety of pharmaceutical companies.


Dr. Botros received her medical degree from the Alexandria University School of Medicine in Egypt. She is fluent in English, French and Arabic.

2018 – 2020 Statistics

Therapeutic Areas

Clinical Trials

Patients Enrolled



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Reaching new heights in clinical research

Our Centers of Excellence provide unparalleled medical and scientific support in the design and execution of clinical trials. Our attention to detail assures quality, reliable results, and has helped CenExel to consistently achieve and exceed patient recruitment goals. We deliver the expertise, engagement, and results to ensure our clients achieve their clinical research goals.

To speed up study implementation, we provide centralized budgeting and contracting for sponsors engaging multiple Centers of Excellence. The geographic diversity of our network offers strong access to roughly 35 million subjects while our broad therapeutic expertise enables a variety of clinical trial strengths.

Top Therapeutic Areas of Expertise

Alzheimer’s Disease
Anxiety Disorder
Bipolar Disorder
Depressive Disorders
Parkinson’s Disease

Seasonal Influenza
Pandemic Influenza

Acute Post-op Pain:
Open Hernia Repair
Wisdom Tooth Extraction

Healthy Volunteer (all ages)
Sleep Apnea
Women’s Health

Meet our Centers of Excellence

Click on any highlighted state to see our Centers of Excellence

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