Human testing started Monday in Brazil on a controversial anti-cancer medicine that has been distributed in the country for years without having gone through proper trials.

The drug, a synthetic phosphoethanolamine known widely as "the cancer pill," was beginning testing with 10 patients at the Sao Paulo Cancer Institute, the Sao Paulo state health department said.

None of those taking part in the trial are being treated with any other drugs, a statement said. If no serious side effects are noted, the trial will then be expanded to up to 1,000 people.

The pill was created by Sao Paulo University professor Gilberto Orivaldo Chierice in the 1990s. Despite claims of a miracle cure, there has been little evidence of its efficacy.

Chierice's drug was not tested but after entering into use in one Sao Paulo hospital word rapidly spread, boosting demand, until Sao Paulo University's chemistry institute was making 50,000 capsules a month without any government oversight.

Distribution was halted in 2014 amid growing doubts in the scientific community about the safety. But in April, president Dilma Rousseff—who was just about to be suspended from her post in an impeachment trial—signed a law legalizing the substance.

Shortly after the Supreme Court overruled her and said the medicine's distribution would depend on it going through proper testing.