The UK pharma giant is clearly impressed by Anacor's boron-based drugs, having committed over $2.5bn to a discovery-stage alliance.
The deal covers the wide-remit of viral and bacterial diseases and GSK will choose at least eight potential drugs against four undisclosed targets.
The Californian biopharma firm will be primarily responsible for moving the drugs through to proof-of-concept before GSK decides whether to pursue them further.
Boron is a relatively underutilised element in pharmaceutical products and could hold a number of advantages over carbon-based molecules.
Firstly, boron compounds have a unique geometry that geometry that allows them to have two distinct shapes.
This could enable them to inhibit normally difficult targets, according to Anacor.
Secondly, boron-based compounds can interact with a biological target to create a change that is specific to a particular disease or condition.
A spokesperson for GSK told DrugResearcher.com that it was this novel chemistry, including the ability to modulate biological targets, which really attracted GSK, especially since it is an area they have little experience in and so can learn a lot from the collaboration.
Zhi Hong, head of GSK's Infectious Diseases Centre of Excellence for Drug Discovery (CEDD), said: "We recognise the issues created by resistance to available medicine and are determined to take advantage of novel approaches that offer new prospects for treatments across a range of infectious diseases."
This style of deal is becoming more common (in fact, it's a setup reminiscent of the deal Pfizer signed with Icagen back in August), where big pharma companies seem increasingly unwilling to wait until proof-of-concept has been established, instead signing contracts almost on a 'first refusal' basis for very early stage projects.
This concept makes sense for both parties: GSK get exclusive rights to a number of drugs without having to spend much money (for them); and Anacor gets the big deal most shareholders want without first having to establish their drug works and the small fee will keep them going until they can.
In this case, Anacor will receive $12m upfront, a $10m equity investment and total milestone payments of between $252m and $331m for each product candidate (a total deal size of over $2.5bn).
This is over twice the industry average for a 2006 discovery-stage deal, which stands at similar amounts upfront and in equity but only around $150m in milestones, according to figures from Recombinant Capital.
However, compare GSK's deal to the one Schering-Plough signed with Anacor in March of this year for its lead drug, AN2690, which is due to enter Phase III trials in 2008: $40m upfront, $10m equity investment, all development and commercialisation costs and up to $505m in milestones for onychomycosis are met and more if other indications are sought.
This is precisely the stage GSK will be given the option of whether to pursue the development of not, only the milestone payments of over $150m less per product.
With the average size of a Phase II deal hovering around $300m across the industry, suddenly the GSK deal doesn't seem so expensive, merely the norm.
Of course the indications may be making a difference to the price but since GSK is unwilling to divulge them for this latest deal, it is impossible to tell.
However the global market for onychomycosis drugs is estimated to grow to $3.6bn in 2010 but with a huge variety of bacterial and viral diseases to choose from, GSK could be expected to target some large indications itself.