The company, which is about to start a two-week roadshow of UK institutions, has caught the eye of institutional investors in Israel and the US.
The strong interest in XTL, which has signed product agreements with market leaders like Eli Lilly and Roche, has prompted its advisers, WestLB Panmure, to consider raising its issue price. Analysts have revalued XTL at as much as $375m (E416m).
It also provides further evidence of continuing optimism in the European biotech sector. Weston Medical, a drug delivery company, debuted on Friday with a 6.5p rise from its issue price.