GSK's event began in September with a two-day commercial briefing for 250 GSK sales and brand team staff.
The second part of the event comprises trade presentations. These will take the form of an experiential installation enabling GSK brands to engage, educate and interact with business partners over three months.
GSK anticipates that buyers and contacts from more than 70 client organisations will attend the second part of the event.
GSK appointed Sledge following the agency's work on a previous event this year.
GSK spokesman Tim Pemberton said: "Following the success of our internal sales briefing in May this year, we decided to reappoint Sledge as it demonstrated an understanding of our briefs, the brands and the importance of delivering quality within the budget.
"Sledge has met our objectives of communicating with our colleagues in an engaging and interactive way and we are confident we can achieve this high level of engagement with our business partners too," said Pemberton.