(Reuters) - Gelesis, founded by biotech firm PureTech Health, will list on the New York Stock Exchange through a merger with an acquisition vehicle, valuing the weight management firm at about $1.3 billion. Gelesis will merge with Capstar Special Purpose Acquisition Corp, sponsored by affiliates of Capstar Partners LLC and funds managed by bond giant PIMCO, PureTech said on Monday. Special purpose acquisition companies, or SPACs, are shell companies that raise funds via an initial public offering to take a private company public through a merger at a later date. Gelesis, London-listed PureTech’s third publicly-traded founded entity, is expected to receive proceeds of up to $376 million from the transaction. The U.S. Food and Drug Administration approved Gelesis’ flagship product Plenity in 2019. The pill, when consumed, becomes a substance that expands in the stomach to reduce space available for food, helping people eat less.