Chinese fintech giant Ant Group was all set to celebrate the biggest initial public offering the world had ever seen. Then, just two days before the scheduled record-breaking $37 billion dual-listing in Hong Kong and Shanghai, Chinese regulators pulled the plug.

Based in Hangzhou, Ant Group operates one of China’s most popular mobile financial apps— Alipay. It is also a close affiliate of Chinese e-commerce giant, Alibaba Group.

For the Hong Kong listing, Simpson Thacher & Bartlett was advising on Hong Kong and U.S. law, with Fangda Partners serving as Chinese counsel. Freshfields Bruckhaus Deringer was representing joint sponsors Citigroup, J.P. Morgan Securities, Morgan Stanley and China International Capital Corp. on Hong Kong and U.S. law, with King & Wood Mallesons acting as Chinese counsel.