The only melanoma treatment currently funded by Pharmac is not ideal for treating the disease, a representative says.
Both Australia and the UK subsidise pembrolizumab (Keytruda) which can stall and shrink tumours in some patients but, in New Zealand, Pharmac has declined to fund it.
Pharmac director of operations Sarah Fitt told Checkpoint with John Campbell that the clinical committees that advise Pharmac had not rejected Keytruda, but had given it a low priority.
Keytruda is expensive: un-funded, the drug costs over $10,000 a month.
Yesterday, melanoma survivor Leisa Renwick told Checkpoint the drug had saved her life.
But Ms Fitt said Pharmac's advisory committees were not satisfied the drug represented clinical value for the cost of the therapy.
"It wasn't actually a 'no', both committees gave it a low priority, they thought the drug looked promising, but it's still fairly early days.
"So we are continuing to work with the suppliers of a number of drugs in this class to look at the efficacy, to look at the clinical trial data."
She said Pharmac looked at data for Keytruda supplied by the company, and also independent advice. It concluded that, while drug gave a response, it still had doubts.
"We want to see survival benefit. It's an expensive treatment and we want to be sure that we are giving a drug that's giving a good response to these patients in the longer term."
Ms Fitt said that, although Australia had decided to fund the drug, the Australian drug funding agency had also raised questions about the drug's efficacy, similar to those raised by Pharmac.
Ultimately Pharmac had to consider the whole population and the best heath outcomes for "all New Zealand patients", she said.
She acknowledged that a chemotherapy treatment currently funded, Dacarbazine, was not ideal for treating melanoma.
"We acknowledge that there definitely is a need for better treatments in this area.
"We need to weigh-up the evidence around this medicine against evidence for other medicines that at the moment offer better and more certain value than this agent does at the moment."