SAN ANTONIO – The South Texas Allergy & Asthma Medical Professionals (STAAMP) research center is offering thousands of patients the brand name anticoagulant drug Xarelto for free to those with a positive COVID-19 test, mild to moderate symptoms and an underlying risk factor for the virus. The Bill and Melinda Gates Research Institute made the Xarelto trial possible. Dr. Gonzalez said COVID-19 positive patients with an underlying medical condition that puts them at high risk should call STAAMP at 210-980-7711 or visit staampallergy.com. The underlying medical conditions can include asthma, respiratory diseases, autoimmune diseases, heart disease, high blood pressure, diabetes and obesity. STAAMP Research is one of six centers nationwide chosen for the trial.