Baxalta jumped to a four-and-a-half-month high yesterday on reports that rival drug maker Shire — the US firm formally based in Ireland — is in advanced talks to acquire it.

Pharmaceutical giant Shire, which is headquartered in Ireland for tax purposes, has agreed to buy US rare disease specialist Dyax Corp for about $5.9bn (€5.35bn), and potentially up to $6.5bn, while still pursuing a five- times larger unsolicited bid for biopharma firm Baxalta Inc.