The Shanghai Stock Exchange has reprimanded a Chinese biotech company over claims that it was manufacturing an experimental drug to treat coronavirus.

Suzhou-based BrightGene Bio-Medical Technology 688166, +0.20% said in early February that it had received approval to make remdesivir, the only drug thought to be effective in treating the virus, according to the World Health Organization.

However, the Shanghai bourse said on Sunday that BrightGene had not obtained approval from China’s drug regulators or authorization from the patent owner, U.S. drugmaker Gilead Sciences GILD, -1.26% , to manufacture the drug in large quantities.

Shares in BrightGene, which spiked almost 60% on Feb. 12 after the company said it had managed to mass produce remdesivir, fell 20% on Monday, the daily limit of the stock exchange.

Remdesivir has been used treat the Ebola virus, the Middle Eastern Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). It might be also be effective for treating patients infected with the COVID-19 virus, according to The University of Alberta’s Li Ka Shing Institute of Virology.

Gilead said on Feb. 26 that it had initiated two late-stage studies to test the safety and efficacy of remdesivir in nearly 1,000 patients with COVID-19 at medical centres across Asia, as well as in other countries with high numbers of diagnosed cases.

There are now a total of 3,048 deaths from coronoavirus, according to the latest figures from the Johns Hopkins University tracker.

BrightGene’s censure comes after the Securities and Exchange Commission last month warned investors about investment frauds involving claims that a company’s products or services could be used to help stop the coronavirus outbreak.

“We have become aware of a number of Internet promotions, including on social media, claiming that the products or services of publicly-traded companies can prevent, detect, or cure coronavirus, and that the stock of these companies will dramatically increase in value as a result,” the SEC said.