PADUCAH, Kentucky — Two Kentucky men have been indicted on federal charges of selling an extremely powerful designer drug recently declared a controlled substance that left a man dead of an overdose and hospitalized his teenage brother.

Jevan Sheppard, 25, and Thomas Jared Hardin, 23, of Calvert City, are accused of selling the powerful synthetic opioid U-4770 — also known as U-4 or Pink — which led Taylor and Karson May to overdose.

The May brothers were found unresponsive in a Calvert City home in March after using U-4. Taylor, a 23-year-old construction worker, was declared dead at the scene. His brother Karson, an 18-year-old college student, was revived at a local hospital.

Investigators later determined that the May brothers had purchased the drugs from Hardin, who had acquired it from, Sheppard, who had allegedly imported it from a laboratory in China, prosecutors said. When Sheppard was arrested, police seized a stash of drugs that had been packaged for sale, a cache of weapons, including assault rifles, and $20,000 in cash from his home.

If convicted, Sheppard and Hardin face a mandatory minimum sentence of 20 years with no parole. Hardin faces additional manslaughter charges in a Kentucky state court, where Sheppard also faces drug trafficking charges. Both have pleaded not guilty.

In late 2016, the Drug Enforcement Agency temporarily declared U-4 a schedule one controlled substance. Eight times more powerful than heroin, U-4770 was developed in the 1970s by pharma giant Upjohn as a less addictive morphine substitute, but was never tested on humans.

Despite the new classification, the drug continues to be manufactured in China and remains readily available online. Officials say the drug has been linked to multiple fatal overdoses around the country and was among the stash of drugs recovered from singer Prince’s home after he died of an overdose in April 2016.