Pharmac's experts committee last week granted it low-priority status because of uncertainty about its benefits and its high cost -- about $300,000 a patient for two years' treatment.
Mr Little said there was a case for political intervention into areas of clinical judgment.
"You set up a system with a level of independence for obvious reasons for clinical judgments but they are clinical judgments for resource allocation.
"I think there is a case for politics where the circumstances are such you've got widespread incidence of the condition that you've got a drug for and it is used in other countries.
"If the reason it is accorded low priority is because they are awaiting more data, I think those are circumstances where politics can intervene and say 'we are not going to deny this to New Zealanders pending more data'."
Paul Smith, New Zealand director of Merck Sharp and Dohme which supplies Keytruda, said 70 per cent of patients either had tumours shrink or stabilise with treatment.
Melanoma is New Zealand's fourth most commonly registered cause of cancer with 2300 new cases each year. Three hundred and fifty people die of it each year.
National politicised the funding of Herceptin in the 2008 election campaign, promising to fund a 12-month course of the dug used in the treatment of breast cancer instead of the nine-week treatment Pharmac was previously funding.
Pharmac's combined pharmaceutical budget for the year ended June 30:
• 2015 - $795 million
• 2014 - $795 million
• 2013 - $783.6 million
• 2012 - $777.4 million
• 2011 -$706.1 million
• 2010 - $693.8 million
• 2009 - $653 million
• 2008 - $635.4 million
