Isis Pharmaceuticals has kicked off a Phase I study of an antiviral candidate partnered with GSK, triggering a $3 million milestone payment from the latter firm.

Details are somewhat scant, with the firms saying only that the antisense drug ISIS-GSK3Rx has been designed - with Isis' discovery platform - to inhibit the production of an undisclosed target to treat a common viral infection. 

B. Lynne Parshall, chief operating officer of Isis, also revealed that the study was being undertaken within a therapeutic area "where there is a significant need for better therapies".

Isis will develop the product to Phase II proof-of-concept, after which point GSK can opt to in-license the program and further progress its development. 

Under their 2010 pact to identify and develop new drugs for rare and serious diseases, the US group also stands to receive additional pre-licensing milestone payments as the drug advances, as well as double-digit royalties on future sales.