All of Uma Gunasekaran’s patients have diabetes, and most are uninsured. The most severe cases might end up with amputated limbs or on dialysis. Gunasekaran, an endocrinologist who runs Parkland Health’s Global Diabetes Program, in Dallas, relies on the benevolence of multibillion-dollar pharmaceutical companies to supply her patients with medicines at no cost.Among the array of diabetes treatments, those in greatest demand are part of a relatively new class of drugs. These are sometimes referred to broadly as Ozempic, after the brand name of the best-known drug of its kind on the market. They work by mimicking the effects of a hormone produced in the gut, glucagon-like peptide-1, or GLP-1, which regulates blood sugar, slows the stomach’s emptying process, and fosters a sensation of fullness…