Chinese healthcare firm JD Health will reportedly raise as much as $4 billion in its upcoming Hong Kong initial public offering, making it one of the biggest IPOs of 2020.

JD Health, a subsidiary of Chinese e-commerce giant JD.com, will raise as much as $3.5 billion in the listing and could raise an additional $500 million in a green shoe option, a provision that grants the underwriter the right to sell investors more shares than initially planned by the issuer if demand proves higher than expected, the Financial Times reported on Wednesday. The listing would value the company at an estimated $28.5 billion.

The estimated numbers for JD Health's debut, which is slated for Dec. 8, would make it one of the biggest listings in Hong Kong this year and the first big Chinese technology listing since the last-minute suspension of Chinese fintech firm Ant Group's blockbuster IPO in Hong Kong and Shanghai.

JD Health provides online healthcare services for customers in China, including online health consultations with doctors and an online pharmacy offering products to both wholesale and retail customers. The company made $1.3 billion in revenue in the first half of 2020, representing a 76% year-on-year revenue increase.

Starting in late January, at the start of the coronavirus outbreak in China, JD Health made online health consultations free for its users. Between January and May, JD Health's online consultation platform recorded an average of over 120,000 daily consultations, compared to around 60,000 before the pandemic.

JD Health had 72.5 million annual active users as of June 30. Its pharmacy arm holds a dominant 30% market share in China's online retail pharmacy market, according to the firm's filing prospectus. JD Health's IPO will be Asia's biggest healthcare IPO ever, beating Japanese pharmaceutical firm Otsuka Holdings' $2.3 billion 2010 IPO, according to Bloomberg.

The company's rivals include Tencent-backed Wedoctor, Hong Kong-listed Pingan Good Doctor, and Ali Health, the healthcare affiliate of e-commerce giant and JD.com competitor Alibaba Group.

JD Health's IPO will place it among the biggest IPOs in Hong Kong this year, a bracket that includes parent company JD.com, which holds an 81% stake in JD Health. In June, JD.com raised $4.4. billion in a secondary listing in Hong Kong.

Nasdaq-listed JD.com is one of several U.S.-listed Chinese firms to pursue secondary offerings closer to home to raise more capital and offset potential regulatory risks facing Chinese companies listed on U.S. exchanges. That trend has resulted in a windfall for Hong Kong's exchange, with secondary IPOs from Chinese firms like JD, gaming company NetEase, and restaurant giant Yum China.