June 15 (Reuters) - Doximity Inc, a social network for doctors, is looking to raise nearly $536 million through a U.S. initial public offering, targeting a valuation of about $4 billion, according to a regulatory filing on Tuesday. The San Francisco-based company plans to sell 23.3 million shares priced between $20 and $23 per share. About 19 million shares will be sold by Doximity, while roughly 4.3 million shares are being offered by existing investors. The offering comes at a time when numerous firms are cashing in on a boom in the health tech sector, which has received a boost from the COVID-19 pandemic. Founded in 2010, Doximity offers a cloud-based digital platform for medical professionals and free membership for physicians. It has more than 1.8 million members on its platform as of March 31, the filing showed. The company has applied to list its shares on the New York Stock Exchange under the ticker symbol "DOCS". Morgan Stanley, Goldman Sachs and J.P. Morgan are the lead underwriters for the offering. Reporting by Sohini Podder in Bengaluru; Editing by Ramakrishnan M. Our Standards: The Thomson Reuters Trust Principles.