Interest on the new funds will be a rate of 10% annually with repayments starting on 1 May and the final repayment due on 1 February.
The facility was set up just under two years ago with a maximum draw down of US$10mln. The latest loan tranche will be used for working capital. It is secured on 7.77mln shares of Kromek and 14.9mln shares of Motif Bio.
Richard Morgan, Amphion’s chief executive, said: "We continue to believe in the future upside potential of our holdings in both partner companies, Kromek and Motif Bio.
“We are working on moving other programmes forward and this facility gives us access to additional working capital to progress the business' pipeline while these two partner companies develop further."
Graham Lumsden, CEO of Motif Bio, said: "We welcome Amphion's continued commitment as a shareholder in Motif Bio."