Vorasidenib, known by the brand name Voranigo, is one of several medicines approved in August for subsidised access on the Pharmaceutical Benefits Scheme.
The pill slows the progression of a rare and incurable type of brain cancer called IDH-mutant astrocytoma and oligodendroglioma.
The slow-growing tumour is caused by a genetic mutation.
The addition of the pill to the scheme marks a breakthrough for patients and oncologists who have previously relied on surgery, radiotherapy and chemotherapy to treat the cancer.
Its degenerative effects include seizures, cognitive changes, physical disability and loss of independence.
"Access to vorasidenib through the PBS provides clinicians with a targeted treatment option, adding another tool to the toolbox and supporting greater choice when discussing treatment options with patients," Peter McCallum Cancer Centre medical oncologist Jim Whittle said.
Victorian woman Leah Ferguson was diagnosed with the cancer two and a half years ago, just months after giving birth to her daughter Lulu.
She underwent surgery to remove the tumour, but doctors were forced to leave behind a small section in a part of the 38-year-old's brain too dangerous to operate on.
Ms Ferguson said Voranigo, which she started taking two years ago, had helped allay anxiety surrounding her remaining tumour.
"It's that sense of hope to have an option not to have to think about it every day and to know that I'm doing all I can to delay any progression," she told AAP.
"The main thing I wanted was more time with my daughter ... I can have this quality of time and just think about doing the fun things, living with Lulu and my family."
Before it was listed on the government's affordable medicine scheme on August 1, the drug came with a $28,000-per-month price tag.
Health Minister Mark Butler said the medicine could help 135 Australians diagnosed with the disease every year, most of whom were younger than 45.
"Tragically, this hits people in very young adulthood, usually in their 20s and 30s, and is deeply, deeply debilitating," he told News24 on Sunday.
The subsidised treatment is eligible to adults and adolescents aged 12 years and older who have not previously received systemic anti-cancer therapy or radiotherapy.
Several other medicines have also been added to the scheme or had access expanded from August.
Subsidies for cancer treatment Selpercatinib have been expanded to include people with a rare form of thyroid cancer.
Tafasitamab, an immunotherapy treatment for a rare type of slow-growing blood cancer, has been listed for the first time, potentially helping 600 Australians diagnosed each year with relapsed or refractory follicular lymphoma.
Access to government discounts on two medicines that treat the chronic bowel illness Crohn's disease, Adalimumab and Infliximab, has been expanded to include children.
The addition of the anti-inflammatory medications to the scheme could slash pharmacy costs from $500 to $25 a script for more than 400 children.
