TORONTO -- Ontario's health minister promised Wednesday to review the criteria for a drug that helps patients with a rare disorder known as PKU after advocates complained no one was actually qualifying for the medication.

"I think it's prudent and responsible for us to have another peek at the data to see if in fact we've got the right criteria or if they should be adjusted," Eric Hoskins said after PKU patients and supporters held a news conference at the legislature.

The drug called Kuvan, which costs $70,000 a year, helps some patients with PKU, an inherited, brain-threatening disorder where the body can't process an essential amino acid found in dietary protein. Patients must eat what advocates call "the most restrictive medical diet known to science," and without medication face symptoms ranging from mild cognitive impairment to severe intellectual disability.

Ontario agreed to cover Kuvan on a case-by-case basis for some patients in 2013, but not one met the qualifications to have the drug paid for by the province, said John Adams, CEO of the Canadian PKU and Allied Disorders group.

"After two years, not a single patient has access to this drug through the Ontario drug program," said Adams, whose 28-year-old son has PKU. "Ontario's highly restrictive criteria are preventing patients from qualifying for public funding for this brain-protecting treatment."

Patients must meet three medical criteria to qualify for Kuvan, added Adams.

"They say you have to meet A and B and C and the solution is it should be A or B or C," he said.

The Progressive Conservatives welcomed Hoskins' decision to review the criteria for Kuvan as a "good first step," but insisted the system for patients to access such drugs is not working as it should.

If people are being denied access to Kuvan and specialists in PKU say the criteria could be better, it's important the province take a look at them, added Hoskins.

"Especially with rare diseases, it's hard to get the clinical evidence early on, and the data that's available and the evidence can change fairly rapidly," he said.

Tory MPP Michael Harris wants an all-party committee to look at the 7,000 rare diseases and disorders that affect small numbers of people so they don't have to keep going to Queen's Park "cap in hand" looking for financial help.

"Instead of dealing with the larger problem of how our health-care system funds drugs for these rare diseases, we have seen time and again government offering little more than stop-gap measures, usually only when public pressure has been applied," he said.

Hoskins was cool to the idea of a committee, and said the issues are best dealt with by a relatively new national process, the common drug review, which determines which medications the provinces should list on their drug plans.

"We worked hard to de-politicize the process," he said. "We've got something good going here and I think it's more important to look at the existing process and how we can refine and support that so it works even better."

Ontario started screening newborns for PKU 50 years ago.