(909) 981-6644 | Fax: (909) 981-5048 info@groveinternalmedicine.com

About Us


Sean To, MD

Sean S. To, M.D.

Dr. Sean S. To graduated from Chicago Medical School in 1998 and completed his internship and residency at the University of Southern California/Los Angeles County Hospital and Akron General Medical Center in Ohio. He has been practicing medicine since 2001.

With his specialty in Internal medicine, he applies scientific knowledge and clinical expertise to the diagnosis, treatment, and compassionate care of adults across the spectrum from health to complex illness. Dr. To is joined by David Kirshbaum, PA-C; together they specialize in treating complex conditions such as: hypertension, diabetes, high cholesterol, COPD, congestive heart failure, osteoporosis and geriatric care.

Dr. To is a dedicated physician who keeps current on advances in medicine to enhance his patient care. His utmost passion is to provide the highest quality of care and to establish long and rewarding personal relationships with his patients. He is happily married to his wife and they have three sons. In his spare time he enjoys reading, ballroom dancing, golfing and spending time with his family.



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David Kirshbaum, PA-C

David Kirshbaum, PA-C

David Kirshbaum, PA-C graduated from Western University in Pomona in 1998. He has been working since then under the supervision of Dr. Robert J. Kirshbaum and Dr. Sean To in Rancho Cucamonga. David is well trained in internal medicine and complex medical problems. Dr. To and David Kirshbaum, PA-C have participated in continuing medical education courses in order to stay current with the latest diagnosis and treatments. They are currently affiliated with San Antonio Hospital. He believes that in health care, success is driven by patient satisfaction, and that success is earned one patient at a time.

david care philosophy


Erika McAlister

Erika McAlister, MMS, PA-C

Erika McAlister, PA-C graduated with her Master of Medical Science from Marshall B. Ketchum University in Fullerton, following an undergraduate degree in Exercise Science. She has many years of experience in obesity management and specializes in exercise and nutritional counseling to assist in weight reduction and better management of chronic health conditions. With her training and prior clinical experience, she is equipped to provide health assessment, diagnosis, education, and treatment of acute and chronic illnesses alongside Dr. Sean S. To and David Kirshbaum, PA-C. Erika is passionate about empowering her patients with the knowledge and guidance needed to make impactful, preventative, and restorative lifestyle changes. In her free time, she enjoys exploring new hikes & beaches, long-distance cycling, camping, and spending time with her husband.

erika care philosophy