Table 1. Summary of ongoing clinical studies of metformin and immune checkpoint inhibitors combination therapy in nondiabetic patients with cancer.

No.	NCT Number	Title	Study design	Enrollment	Status	Diseases	Interventions	Sponsor	Start date
1	NCT03994744	Assessing Safety and Efficacy of Sintilimab and Metformin Combination Therapy in SCLC	Phase 2 Open Label	68	Recruiting	ED-stage SCLC patients resistant to or relapsed after standard chemotherapy	PD-1 inhibitor Sintilimab plus Metformin	Hunan Cancer Hospital, China	20-Aug-2019
2	NCT03800602	Nivolumab and Metformin in Patients With Treatment Refractory MSS Colorectal Cancer	Phase 2 Open Label	28	Recruiting	MSS stage IV colorectal cancer	Nivolumab plus Metformin	Emory University Hospital, Emory Saint Joseph's Hospital, United States	15-Jan-2019
3	NCT03618654	Durvalumab With or Without Metformin in Treating Participants With Head and Neck Squamous Cell Carcinoma	Phase 1 Randomized Open Label	38	Recruiting	Head and neck squamous cell carcinoma	Durvalumab vs Durvalumab plus Metformin	Sidney Kimmel Cancer Center at Thomas Jefferson University, United States	1-Nov-2018
4	NCT03311308	A Trial of Pembrolizumab and Metformin Versus Pembrolizumab Alone in Advanced Melanoma	Phase 1 Non-Randomized Open Label	30	Recruiting	Advanced Melanoma	Pembrolizumab vs Pembrolizumab plus Metformin	University of Pittsburgh Medical Center Hillman Cancer Center, United States	6-Dec-2017
5	NCT03048500	Nivolumab and Metformin Hydrochloride in Treating Patients With Stage III-IV Non-small Cell Lung Cancer That Cannot Be Removed by Surgery	Phase 2 Open Label	51	Recruiting	Recurrent or Stage III-IV NSCLC	Nivolumab plus Metformin	Northwestern University, United States	6-Jun-2017
6	NCT04114136	Anti-PD-1 mAb Plus Metabolic Modulator in Solid Tumor Malignancies	Phase 2 Open Label	108	Not yet recruiting	Solid Tumor Malignancies	Anti-PD-1 mAb (nivolumab or pembrolizumab) plus Metformin vs Anti-PD-1 mAb (nivolumab or pembrolizumab) plus Rosiglitazone	UPMC Hillman Cancer Center, United States	15-Oct-2019

Abbreviation: SCLC: small cell lung cancer, ED-stage: extensive stage disease, PD-1: programmed cell death protein 1, MSS: microsatellite stable, NSCLC: non-small-cell lung cancer.