What made PureTech different, however, was that it was also developing its own pipeline of drugs, having signed a partnership agreement with Swiss drugs giant Roche last month. The deal was to use microscopic sacs - or 'exosomes' - which are found in milk, as a route of oral administration for biological treatments. Apparently, the ingredient could help the ingredients survive the harsh, acidic environment of a patient's stomach, and could be worth up to $1bn to PureTech. Meddings said much of the company's risk in its portfolio companies was shared with investors, including Amgen Ventures, Baillie Gifford, and the Wellcome Trust. However, PureTech's share price has been a roller coaster ride since floating at 160p in 2015, with the firm closing at 154p on Friday, putting a value of £441.9m on it. The Nasdaq listing, $100m fundraising, and a string of positive trial results had failed to put any fire under the share price, which had risen less than 4% since the beginning of the year.