Immutep (ASX:IMM) shares have risen six per cent to a three-week high after its lead drug candidate was granted a US patent and the world’s largest asset manager upped its stake in the Sydney immunotherapy company.

The patent “combined preparations for the treatment of cancer or infection” covers Immutep’s eftilagimod alpha (“efti”) when combined with Merck’s “miracle” anti-cancer drug Keytruda or Bristol Myer Squibb’s Opdivo.

Both drugs are known as PD-1 pathway inhibitors, which work by blocking a method cancer cells use to hide from the body’s immune system. (In Australia, Imugene (ASX:IMU) is developing its own PD-1 inhibitor, and a number of other companies have drugs in development).

Immutep and Merck last month expanded their phase 2 study testing how well efti and Keytruda work together to fight head and neck cancer, after early data showed “very encouraging” results in a small number of patients. It’s also being tested in breast and non-small lung cancer.

Immutep chief scientific officer Dr Frédéric Triebel said the US patent “represents another important milestone for the company, and along with the clinical data we have seen from our trials, supports our long-held view that combining efti with an anti-PD-1 checkpoint inhibitor should result in a very meaningful therapeutic benefit to cancer patients.”

BlackRock ups IMM holdings

Separately, Immutep disclosed that American multinational investor BlackRock Group (NYSE:BLK) had upped its stake in the company from 6.6 per cent to 7.9 per cent.

BlackRock took an initial “substantial holding” of 5.3 per cent of Immutep on December 22, and has been adding to its position since then.

Around noon, Immutep shares were up 6.4 per cent to 42c, their highest level since December 11.