The U.S. Federal Trade Commission has granted Novartis permission to acquire the GlaxoSmithKline (GSK) oncology portfolio - with some strings attached.

Canada's competition authority also has agreed to allow the $16 billion deal announced in April 2014.

In exchange for the US blessing, the Swiss drugmaker has agreed to divest assets related to its BRAF and MEK inhibitor drugs, now in development to treat melanoma, to Colorado-based Array BioPharma.

The FTC's green light applies to all parts of the envisioned complex transaction.

Along with the cancer drug deal, GSK will acquire Novartis' global vaccine business, apart from its flu vaccines. In the third component of the asset swap, the two companies would create a joint consumer healthcare business.

The US authority said the divestment of the inhibitors was needed as Glaxo and Novartis are among only a few companies active in this business segment.