"Smart pill" firm Proteus raises $172 million

July 29 (Reuters) - A U.S. biotech company pioneering tablets containing embedded microchips that can tell if patients have taken their medication has raised a further $172 million, showing investor interest in its ingestible and wearable technology.

Privately held Proteus Digital Health, which is working with drugmakers including Novartis (Xetra: 904278 - news) and Otsuka (Other OTC: OSUKF - news) , said on Tuesday the funding was one of the biggest U.S. private financings this year and the largest in the digital health sector.

Proteus already has European and U.S. approval for its "smart pill" technology system, in which a tiny sensor is embedded in a tablet and linked to a patch worn on the patient's abdomen.

About the size of a grain of sand, the sensor has no battery or antenna and is powered by reacting with stomach juices. Information is sent from the sensor to the small skin patch, which transmits data by Bluetooth to a smartphone or tablet computer.

In addition to telling doctors if patients are taking their medicines properly, the tiny sensors can also monitor vital signs, such as heart rate.

Earlier this year the Redwood City, California-based group announced it was establishing its first international manufacturing site in Britain.

Proteus's funders include Carlyle, Essex Woodlands, Kaiser Permanente, Medtronic (NYSE: MDT - news) , Novartis, Otsuka, Oracle (NYSE: ORCL - news) and ON Semiconductor (NasdaqGS: ONNN - news) . The company said the latest fundraising involved additional unidentified institutional investors. (Reporting by Ben Hirschler; Editing by David Holmes)