Melanoma sufferers could soon have a new drug that's proven to shrink tumours.

MedSafe has approved and registered the immunotherapy 'Keytruda.'

Melanoma New Zealand said it will be the first 'effective' drug available to Kiwis if funding is made available.

The drug is already approved and funded in Australia and the United States.

Chief Executive Officer of Melanoma NZ Linda Flay said New Zealand has the highest rate of melanoma in the world and should be a priority country.

Flay said access to Keytruda is now in the hands of PHARMAC.

She's hoping for a good outcome given New Zealand has the highest incidence of melanoma in the world, alongside Australia.

More than four and a half thousand cases are diagnosed every year.