DPP4 and type 2 diabetes mellitus: Our studies suggest that repurposing DPP4 class of drugs, as treatment option for patients with SARS-CoV-2 (2019-nCov) infections should be thoroughly investigated, which can benefit a number of elderly patients suffering from comorbidities such as type-2 diabetes, who are more susceptible to SARS-CoV-2 infections.