The revamp, announced on Tuesday, is the result of a keenly awaited strategic review at the company.
Chief Executive Joe Jimenez said the changes would focus the company on innovative businesses with global scale. "They also improve our financial strength, and are expected to add to our growth rates and margins immediately," he said.
Novartis said it had agreed to acquire GSK's oncology products for a $14.5 billion payment. The Swiss drugmaker will also divest its vaccines business, excluding flu, to GSK for $7.1 billion plus royalties.
In a separate transaction, Novartis said it had agreed to divest its animal health division to Eli Lilly for approximately $5.4 billion.
The deals mark a major reorganisation for GSK too, which is to return 4 billion pounds to shareholders following the changes. GSK will take the lead in running a future consumer health business with Novartis but will effectively give up its ambitions to be a global leader in oncology.
GSK said the company would in future have a balanced business centered around consumer health, vaccines, respiratory and HIV medicines, which together would account for about 70 percent of revenues.