TigerText, whose customers include leading US hospitals, has closed a $21 million Series B round led by investment firm Shasta Ventures and joined by health investor Orbimed, Anglo-Dutch publisher Reed-Elsevier and Canadian mobile operator Telus.

The US firm offers secure, real-time mobile messaging for enterprises and has take-up across “dozens of the top 100 hospitals” in the States, it said.

The additional funding will support expansion, off the back of 2013 where sales climbed more than fourfold over the previous year.

Returning Series A investors Easton Capital, new Leaf Venture Partners and New Science Ventures also joined the latest round.