Sullivan's grim outlook had been that Pene would survive just days and no more than a fortnight.
"His personal story is truly remarkable," said Sullivan.
Now, four months later, Pene is planning to return to his job as a supervisor at a pest control company two days a week, partly to help pay for Keytruda, but also because "I've always worked, all my life, so has my wife".
He has had seven infusions of Keytruda. After the third, a scan showed his tumours, caused by mesothelioma in the peritoneum, the lining of the abdomen, had shrunk by 61 per cent. He was exposed to asbestos at a Penrose factory as a 15-year-old during a holiday job at the workplace of his father, whom Leonard said had died of asbestos-related illness in his 60s.
"I've got no pain, I don't take any pills ... no problems."
But financial concerns for the cost of Keytruda are growing. The drug has chewed up more than $34,000 of his and wife Paulette's retirement savings, even with a large discount from the supplier, Merck, Sharp and Dohme.
He said it was "stupid" that Pharmac wouldn't pay for him to have the drug when it does pay for those with advanced melanoma to be treated with it or Opdivo, a similar drug.
Keytruda and Opdivo have had remarkable results in many patients with melanoma, but in others they don't work and there is no way of predicting who will benefit although work is under way on developing tests.
Both drugs are licensed with Medsafe New Zealand for treating lung cancer as well as melanoma, but neither is licensed for mesothelioma, in which there is not yet sufficient evidence of superiority to chemotherapy to seek a licence. A Medsafe licence is generally required before Pharmac will consider funding.
The two drugs, both in the "PD-1 inhibitor" class, are being trialled in numerous cancers, including Keytruda in breast, head and neck and stomach cancers; and Opdivo in bowel, brain, and head and neck cancers. It is unclear how long they should be taken for.
"The highest benefit seems to be melanoma," said Sullivan.
"There is a phase 1 trial of Keytruda in mesothelioma with a response rate around 25 per cent, but as yet we don't know the duration of response as the data is too immature."
He has treated around 20 mesothelioma patients and seen "some amazing responses, Len being one of them."
"The real challenge is trying to perfect the PD-1 testing so we can predict who benefits and who doesn't ... and then make cost effective health investment decisions."
• Leonard Pene's Givealittle page can be found here
